backing: move the min votes threshold to the runtime (#1200)

* move min backing votes const to runtime

also cache it per-session in the backing subsystem

Signed-off-by: alindima <alin@parity.io>

* add runtime migration

* introduce api versioning for min_backing votes

also enable it for rococo/versi for testing

* also add min_backing_votes runtime calls to statement-distribution

this dependency has been recently introduced by async backing

* remove explicit version runtime API call

this is not needed, as the RuntimeAPISubsystem already takes care
of versioning and will return NotSupported if the version is not
right.

* address review comments

- parametrise backing votes runtime API with session index
- remove RuntimeInfo usage in backing subsystem, as runtime API
caches the min backing votes by session index anyway.
- move the logic for adjusting the configured needed backing votes with the size of the backing group
to a primitives helper.
- move the legacy min backing votes value to a primitives helper.
- mark JoinMultiple error as fatal, since the Canceled (non-multiple) counterpart is also fatal.
- make backing subsystem handle fatal errors for new leaves update.
- add HostConfiguration consistency check for zeroed backing votes threshold
- add cumulus accompanying change

* fix cumulus test compilation

* fix tests

* more small fixes

* fix merge

* bump runtime api version for westend and rollback version for rococo

---------

Signed-off-by: alindima <alin@parity.io>
Co-authored-by: Javier Viola <javier@parity.io>

polkadot/runtime/parachains/src/configuration.rs

@@ -24,8 +24,8 @@ use frame_system::pallet_prelude::*;
 use parity_scale_codec::{Decode, Encode};
 use polkadot_parachain::primitives::{MAX_HORIZONTAL_MESSAGE_NUM, MAX_UPWARD_MESSAGE_NUM};
 use primitives::{
-	vstaging::AsyncBackingParams, Balance, ExecutorParams, SessionIndex, MAX_CODE_SIZE,
-	MAX_HEAD_DATA_SIZE, MAX_POV_SIZE, ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
+	vstaging::AsyncBackingParams, Balance, ExecutorParams, SessionIndex, LEGACY_MIN_BACKING_VOTES,
+	MAX_CODE_SIZE, MAX_HEAD_DATA_SIZE, MAX_POV_SIZE, ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
 };
 use sp_runtime::{traits::Zero, Perbill};
 use sp_std::prelude::*;
@@ -245,6 +245,9 @@ pub struct HostConfiguration<BlockNumber> {
 	/// This value should be greater than
 	/// [`paras_availability_period`](Self::paras_availability_period).
 	pub minimum_validation_upgrade_delay: BlockNumber,
+	/// The minimum number of valid backing statements required to consider a parachain candidate
+	/// backable.
+	pub minimum_backing_votes: u32,
 }
 
 impl<BlockNumber: Default + From<u32>> Default for HostConfiguration<BlockNumber> {
@@ -295,6 +298,7 @@ impl<BlockNumber: Default + From<u32>> Default for HostConfiguration<BlockNumber
 			on_demand_fee_variability: Perbill::from_percent(3),
 			on_demand_target_queue_utilization: Perbill::from_percent(25),
 			on_demand_ttl: 5u32.into(),
+			minimum_backing_votes: LEGACY_MIN_BACKING_VOTES,
 		}
 	}
 }
@@ -331,6 +335,8 @@ pub enum InconsistentError<BlockNumber> {
 	MaxHrmpOutboundChannelsExceeded,
 	/// Maximum number of HRMP inbound channels exceeded.
 	MaxHrmpInboundChannelsExceeded,
+	/// `minimum_backing_votes` is set to zero.
+	ZeroMinimumBackingVotes,
 }
 
 impl<BlockNumber> HostConfiguration<BlockNumber>
@@ -411,6 +417,10 @@ where
 			return Err(MaxHrmpInboundChannelsExceeded)
 		}
 
+		if self.minimum_backing_votes.is_zero() {
+			return Err(ZeroMinimumBackingVotes)
+		}
+
 		Ok(())
 	}
 
@@ -477,7 +487,8 @@ pub mod pallet {
 	/// v5-v6: <https://github.com/paritytech/polkadot/pull/6271> (remove UMP dispatch queue)
 	/// v6-v7: <https://github.com/paritytech/polkadot/pull/7396>
 	/// v7-v8: <https://github.com/paritytech/polkadot/pull/6969>
-	const STORAGE_VERSION: StorageVersion = StorageVersion::new(8);
+	/// v8-v9: <https://github.com/paritytech/polkadot/pull/7577>
+	const STORAGE_VERSION: StorageVersion = StorageVersion::new(9);
 
 	#[pallet::pallet]
 	#[pallet::storage_version(STORAGE_VERSION)]
@@ -1153,6 +1164,18 @@ pub mod pallet {
 				config.on_demand_ttl = new;
 			})
 		}
+		/// Set the minimum backing votes threshold.
+		#[pallet::call_index(52)]
+		#[pallet::weight((
+			T::WeightInfo::set_config_with_u32(),
+			DispatchClass::Operational
+		))]
+		pub fn set_minimum_backing_votes(origin: OriginFor<T>, new: u32) -> DispatchResult {
+			ensure_root(origin)?;
+			Self::schedule_config_update(|config| {
+				config.minimum_backing_votes = new;
+			})
+		}
 	}
 
 	#[pallet::hooks]

polkadot/runtime/parachains/src/configuration/migration.rs

@@ -19,3 +19,4 @@
 pub mod v6;
 pub mod v7;
 pub mod v8;
+pub mod v9;

polkadot/runtime/parachains/src/configuration/migration/v8.rs

@@ -23,14 +23,114 @@ use frame_support::{
 	weights::Weight,
 };
 use frame_system::pallet_prelude::BlockNumberFor;
-use primitives::SessionIndex;
+use primitives::{
+	vstaging::AsyncBackingParams, Balance, ExecutorParams, SessionIndex,
+	ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
+};
 use sp_runtime::Perbill;
 use sp_std::vec::Vec;
 
 use frame_support::traits::OnRuntimeUpgrade;
 
 use super::v7::V7HostConfiguration;
-type V8HostConfiguration<BlockNumber> = configuration::HostConfiguration<BlockNumber>;
+/// All configuration of the runtime with respect to paras.
+#[derive(Clone, Encode, Decode, Debug)]
+pub struct V8HostConfiguration<BlockNumber> {
+	pub max_code_size: u32,
+	pub max_head_data_size: u32,
+	pub max_upward_queue_count: u32,
+	pub max_upward_queue_size: u32,
+	pub max_upward_message_size: u32,
+	pub max_upward_message_num_per_candidate: u32,
+	pub hrmp_max_message_num_per_candidate: u32,
+	pub validation_upgrade_cooldown: BlockNumber,
+	pub validation_upgrade_delay: BlockNumber,
+	pub async_backing_params: AsyncBackingParams,
+	pub max_pov_size: u32,
+	pub max_downward_message_size: u32,
+	pub hrmp_max_parachain_outbound_channels: u32,
+	pub hrmp_sender_deposit: Balance,
+	pub hrmp_recipient_deposit: Balance,
+	pub hrmp_channel_max_capacity: u32,
+	pub hrmp_channel_max_total_size: u32,
+	pub hrmp_max_parachain_inbound_channels: u32,
+	pub hrmp_channel_max_message_size: u32,
+	pub executor_params: ExecutorParams,
+	pub code_retention_period: BlockNumber,
+	pub on_demand_cores: u32,
+	pub on_demand_retries: u32,
+	pub on_demand_queue_max_size: u32,
+	pub on_demand_target_queue_utilization: Perbill,
+	pub on_demand_fee_variability: Perbill,
+	pub on_demand_base_fee: Balance,
+	pub on_demand_ttl: BlockNumber,
+	pub group_rotation_frequency: BlockNumber,
+	pub paras_availability_period: BlockNumber,
+	pub scheduling_lookahead: u32,
+	pub max_validators_per_core: Option<u32>,
+	pub max_validators: Option<u32>,
+	pub dispute_period: SessionIndex,
+	pub dispute_post_conclusion_acceptance_period: BlockNumber,
+	pub no_show_slots: u32,
+	pub n_delay_tranches: u32,
+	pub zeroth_delay_tranche_width: u32,
+	pub needed_approvals: u32,
+	pub relay_vrf_modulo_samples: u32,
+	pub pvf_voting_ttl: SessionIndex,
+	pub minimum_validation_upgrade_delay: BlockNumber,
+}
+
+impl<BlockNumber: Default + From<u32>> Default for V8HostConfiguration<BlockNumber> {
+	fn default() -> Self {
+		Self {
+			async_backing_params: AsyncBackingParams {
+				max_candidate_depth: 0,
+				allowed_ancestry_len: 0,
+			},
+			group_rotation_frequency: 1u32.into(),
+			paras_availability_period: 1u32.into(),
+			no_show_slots: 1u32.into(),
+			validation_upgrade_cooldown: Default::default(),
+			validation_upgrade_delay: 2u32.into(),
+			code_retention_period: Default::default(),
+			max_code_size: Default::default(),
+			max_pov_size: Default::default(),
+			max_head_data_size: Default::default(),
+			on_demand_cores: Default::default(),
+			on_demand_retries: Default::default(),
+			scheduling_lookahead: 1,
+			max_validators_per_core: Default::default(),
+			max_validators: None,
+			dispute_period: 6,
+			dispute_post_conclusion_acceptance_period: 100.into(),
+			n_delay_tranches: Default::default(),
+			zeroth_delay_tranche_width: Default::default(),
+			needed_approvals: Default::default(),
+			relay_vrf_modulo_samples: Default::default(),
+			max_upward_queue_count: Default::default(),
+			max_upward_queue_size: Default::default(),
+			max_downward_message_size: Default::default(),
+			max_upward_message_size: Default::default(),
+			max_upward_message_num_per_candidate: Default::default(),
+			hrmp_sender_deposit: Default::default(),
+			hrmp_recipient_deposit: Default::default(),
+			hrmp_channel_max_capacity: Default::default(),
+			hrmp_channel_max_total_size: Default::default(),
+			hrmp_max_parachain_inbound_channels: Default::default(),
+			hrmp_channel_max_message_size: Default::default(),
+			hrmp_max_parachain_outbound_channels: Default::default(),
+			hrmp_max_message_num_per_candidate: Default::default(),
+			pvf_voting_ttl: 2u32.into(),
+			minimum_validation_upgrade_delay: 2.into(),
+			executor_params: Default::default(),
+			on_demand_queue_max_size: ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
+			on_demand_base_fee: 10_000_000u128,
+			on_demand_fee_variability: Perbill::from_percent(3),
+			on_demand_target_queue_utilization: Perbill::from_percent(25),
+			on_demand_ttl: 5u32.into(),
+		}
+	}
+}
 
 mod v7 {
 	use super::*;

polkadot/runtime/parachains/src/configuration/migration/v9.rs

@@ -0,0 +1,321 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! A module that is responsible for migration of storage.
+
+use crate::configuration::{self, Config, Pallet};
+use frame_support::{
+	pallet_prelude::*,
+	traits::{Defensive, StorageVersion},
+	weights::Weight,
+};
+use frame_system::pallet_prelude::BlockNumberFor;
+use primitives::{SessionIndex, LEGACY_MIN_BACKING_VOTES};
+use sp_runtime::Perbill;
+use sp_std::vec::Vec;
+
+use frame_support::traits::OnRuntimeUpgrade;
+
+use super::v8::V8HostConfiguration;
+type V9HostConfiguration<BlockNumber> = configuration::HostConfiguration<BlockNumber>;
+
+mod v8 {
+	use super::*;
+
+	#[frame_support::storage_alias]
+	pub(crate) type ActiveConfig<T: Config> =
+		StorageValue<Pallet<T>, V8HostConfiguration<BlockNumberFor<T>>, OptionQuery>;
+
+	#[frame_support::storage_alias]
+	pub(crate) type PendingConfigs<T: Config> = StorageValue<
+		Pallet<T>,
+		Vec<(SessionIndex, V8HostConfiguration<BlockNumberFor<T>>)>,
+		OptionQuery,
+	>;
+}
+
+mod v9 {
+	use super::*;
+
+	#[frame_support::storage_alias]
+	pub(crate) type ActiveConfig<T: Config> =
+		StorageValue<Pallet<T>, V9HostConfiguration<BlockNumberFor<T>>, OptionQuery>;
+
+	#[frame_support::storage_alias]
+	pub(crate) type PendingConfigs<T: Config> = StorageValue<
+		Pallet<T>,
+		Vec<(SessionIndex, V9HostConfiguration<BlockNumberFor<T>>)>,
+		OptionQuery,
+	>;
+}
+
+pub struct MigrateToV9<T>(sp_std::marker::PhantomData<T>);
+impl<T: Config> OnRuntimeUpgrade for MigrateToV9<T> {
+	#[cfg(feature = "try-runtime")]
+	fn pre_upgrade() -> Result<Vec<u8>, sp_runtime::TryRuntimeError> {
+		log::trace!(target: crate::configuration::LOG_TARGET, "Running pre_upgrade() for HostConfiguration MigrateToV9");
+		Ok(Vec::new())
+	}
+
+	fn on_runtime_upgrade() -> Weight {
+		log::info!(target: configuration::LOG_TARGET, "HostConfiguration MigrateToV9 started");
+		if StorageVersion::get::<Pallet<T>>() == 8 {
+			let weight_consumed = migrate_to_v9::<T>();
+
+			log::info!(target: configuration::LOG_TARGET, "HostConfiguration MigrateToV9 executed successfully");
+			StorageVersion::new(9).put::<Pallet<T>>();
+
+			weight_consumed
+		} else {
+			log::warn!(target: configuration::LOG_TARGET, "HostConfiguration MigrateToV9 should be removed.");
+			T::DbWeight::get().reads(1)
+		}
+	}
+
+	#[cfg(feature = "try-runtime")]
+	fn post_upgrade(_state: Vec<u8>) -> Result<(), sp_runtime::TryRuntimeError> {
+		log::trace!(target: crate::configuration::LOG_TARGET, "Running post_upgrade() for HostConfiguration MigrateToV9");
+		ensure!(
+			StorageVersion::get::<Pallet<T>>() >= 9,
+			"Storage version should be >= 9 after the migration"
+		);
+
+		Ok(())
+	}
+}
+
+fn migrate_to_v9<T: Config>() -> Weight {
+	// Unusual formatting is justified:
+	// - make it easier to verify that fields assign what they supposed to assign.
+	// - this code is transient and will be removed after all migrations are done.
+	// - this code is important enough to optimize for legibility sacrificing consistency.
+	#[rustfmt::skip]
+	let translate =
+		|pre: V8HostConfiguration<BlockNumberFor<T>>| ->
+		V9HostConfiguration<BlockNumberFor<T>>
+	{
+		V9HostConfiguration {
+max_code_size                            : pre.max_code_size,
+max_head_data_size                       : pre.max_head_data_size,
+max_upward_queue_count                   : pre.max_upward_queue_count,
+max_upward_queue_size                    : pre.max_upward_queue_size,
+max_upward_message_size                  : pre.max_upward_message_size,
+max_upward_message_num_per_candidate     : pre.max_upward_message_num_per_candidate,
+hrmp_max_message_num_per_candidate       : pre.hrmp_max_message_num_per_candidate,
+validation_upgrade_cooldown              : pre.validation_upgrade_cooldown,
+validation_upgrade_delay                 : pre.validation_upgrade_delay,
+max_pov_size                             : pre.max_pov_size,
+max_downward_message_size                : pre.max_downward_message_size,
+hrmp_sender_deposit                      : pre.hrmp_sender_deposit,
+hrmp_recipient_deposit                   : pre.hrmp_recipient_deposit,
+hrmp_channel_max_capacity                : pre.hrmp_channel_max_capacity,
+hrmp_channel_max_total_size              : pre.hrmp_channel_max_total_size,
+hrmp_max_parachain_inbound_channels      : pre.hrmp_max_parachain_inbound_channels,
+hrmp_max_parachain_outbound_channels     : pre.hrmp_max_parachain_outbound_channels,
+hrmp_channel_max_message_size            : pre.hrmp_channel_max_message_size,
+code_retention_period                    : pre.code_retention_period,
+on_demand_cores                          : pre.on_demand_cores,
+on_demand_retries                        : pre.on_demand_retries,
+group_rotation_frequency                 : pre.group_rotation_frequency,
+paras_availability_period                : pre.paras_availability_period,
+scheduling_lookahead                     : pre.scheduling_lookahead,
+max_validators_per_core                  : pre.max_validators_per_core,
+max_validators                           : pre.max_validators,
+dispute_period                           : pre.dispute_period,
+dispute_post_conclusion_acceptance_period: pre.dispute_post_conclusion_acceptance_period,
+no_show_slots                            : pre.no_show_slots,
+n_delay_tranches                         : pre.n_delay_tranches,
+zeroth_delay_tranche_width               : pre.zeroth_delay_tranche_width,
+needed_approvals                         : pre.needed_approvals,
+relay_vrf_modulo_samples                 : pre.relay_vrf_modulo_samples,
+pvf_voting_ttl                           : pre.pvf_voting_ttl,
+minimum_validation_upgrade_delay         : pre.minimum_validation_upgrade_delay,
+async_backing_params                     : pre.async_backing_params,
+executor_params                          : pre.executor_params,
+on_demand_queue_max_size                 : 10_000u32,
+on_demand_base_fee                       : 10_000_000u128,
+on_demand_fee_variability                : Perbill::from_percent(3),
+on_demand_target_queue_utilization       : Perbill::from_percent(25),
+on_demand_ttl                            : 5u32.into(),
+minimum_backing_votes                    : LEGACY_MIN_BACKING_VOTES
+		}
+	};
+
+	let v8 = v8::ActiveConfig::<T>::get()
+		.defensive_proof("Could not decode old config")
+		.unwrap_or_default();
+	let v9 = translate(v8);
+	v9::ActiveConfig::<T>::set(Some(v9));
+
+	// Allowed to be empty.
+	let pending_v8 = v8::PendingConfigs::<T>::get().unwrap_or_default();
+	let mut pending_v9 = Vec::new();
+
+	for (session, v8) in pending_v8.into_iter() {
+		let v9 = translate(v8);
+		pending_v9.push((session, v9));
+	}
+	v9::PendingConfigs::<T>::set(Some(pending_v9.clone()));
+
+	let num_configs = (pending_v9.len() + 1) as u64;
+	T::DbWeight::get().reads_writes(num_configs, num_configs)
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::mock::{new_test_ext, Test};
+
+	#[test]
+	fn v9_deserialized_from_actual_data() {
+		// Example how to get new `raw_config`:
+		// We'll obtain the raw_config at a specified a block
+		// Steps:
+		// 1. Go to Polkadot.js -> Developer -> Chain state -> Storage: https://polkadot.js.org/apps/#/chainstate
+		// 2. Set these parameters:
+		//   2.1. selected state query: configuration; activeConfig():
+		//        PolkadotRuntimeParachainsConfigurationHostConfiguration
+		//   2.2. blockhash to query at:
+		//        0xf89d3ab5312c5f70d396dc59612f0aa65806c798346f9db4b35278baed2e0e53 (the hash of
+		//        the block)
+		//   2.3. Note the value of encoded storage key ->
+		//        0x06de3d8a54d27e44a9d5ce189618f22db4b49d95320d9021994c850f25b8e385 for the
+		// referenced        block.
+		//   2.4. You'll also need the decoded values to update the test.
+		// 3. Go to Polkadot.js -> Developer -> Chain state -> Raw storage
+		//   3.1 Enter the encoded storage key and you get the raw config.
+
+		// This exceeds the maximal line width length, but that's fine, since this is not code and
+		// doesn't need to be read and also leaving it as one line allows to easily copy it.
+		let raw_config =
+	hex_literal::hex!["
+	0000300000800000080000000000100000c8000005000000050000000200000002000000000000000000000000005000000010000400000000000000000000000000000000000000000000000000000000000000000000000800000000200000040000000000100000b004000000000000000000001027000080b2e60e80c3c901809698000000000000000000000000000500000014000000040000000100000001010000000006000000640000000200000019000000000000000300000002000000020000000500000002000000"
+	];
+
+		let v9 =
+			V9HostConfiguration::<primitives::BlockNumber>::decode(&mut &raw_config[..]).unwrap();
+
+		// We check only a sample of the values here. If we missed any fields or messed up data
+		// types that would skew all the fields coming after.
+		assert_eq!(v9.max_code_size, 3_145_728);
+		assert_eq!(v9.validation_upgrade_cooldown, 2);
+		assert_eq!(v9.max_pov_size, 5_242_880);
+		assert_eq!(v9.hrmp_channel_max_message_size, 1_048_576);
+		assert_eq!(v9.n_delay_tranches, 25);
+		assert_eq!(v9.minimum_validation_upgrade_delay, 5);
+		assert_eq!(v9.group_rotation_frequency, 20);
+		assert_eq!(v9.on_demand_cores, 0);
+		assert_eq!(v9.on_demand_base_fee, 10_000_000);
+		assert_eq!(v9.minimum_backing_votes, LEGACY_MIN_BACKING_VOTES);
+	}
+
+	#[test]
+	fn test_migrate_to_v9() {
+		// Host configuration has lots of fields. However, in this migration we only add one
+		// field. The most important part to check are a couple of the last fields. We also pick
+		// extra fields to check arbitrarily, e.g. depending on their position (i.e. the middle) and
+		// also their type.
+		//
+		// We specify only the picked fields and the rest should be provided by the `Default`
+		// implementation. That implementation is copied over between the two types and should work
+		// fine.
+		let v8 = V8HostConfiguration::<primitives::BlockNumber> {
+			needed_approvals: 69,
+			paras_availability_period: 55,
+			hrmp_recipient_deposit: 1337,
+			max_pov_size: 1111,
+			minimum_validation_upgrade_delay: 20,
+			..Default::default()
+		};
+
+		let mut pending_configs = Vec::new();
+		pending_configs.push((100, v8.clone()));
+		pending_configs.push((300, v8.clone()));
+
+		new_test_ext(Default::default()).execute_with(|| {
+			// Implant the v8 version in the state.
+			v8::ActiveConfig::<Test>::set(Some(v8));
+			v8::PendingConfigs::<Test>::set(Some(pending_configs));
+
+			migrate_to_v9::<Test>();
+
+			let v9 = v9::ActiveConfig::<Test>::get().unwrap();
+			let mut configs_to_check = v9::PendingConfigs::<Test>::get().unwrap();
+			configs_to_check.push((0, v9.clone()));
+
+			for (_, v8) in configs_to_check {
+				#[rustfmt::skip]
+				{
+					assert_eq!(v8.max_code_size                            , v9.max_code_size);
+					assert_eq!(v8.max_head_data_size                       , v9.max_head_data_size);
+					assert_eq!(v8.max_upward_queue_count                   , v9.max_upward_queue_count);
+					assert_eq!(v8.max_upward_queue_size                    , v9.max_upward_queue_size);
+					assert_eq!(v8.max_upward_message_size                  , v9.max_upward_message_size);
+					assert_eq!(v8.max_upward_message_num_per_candidate     , v9.max_upward_message_num_per_candidate);
+					assert_eq!(v8.hrmp_max_message_num_per_candidate       , v9.hrmp_max_message_num_per_candidate);
+					assert_eq!(v8.validation_upgrade_cooldown              , v9.validation_upgrade_cooldown);
+					assert_eq!(v8.validation_upgrade_delay                 , v9.validation_upgrade_delay);
+					assert_eq!(v8.max_pov_size                             , v9.max_pov_size);
+					assert_eq!(v8.max_downward_message_size                , v9.max_downward_message_size);
+					assert_eq!(v8.hrmp_max_parachain_outbound_channels     , v9.hrmp_max_parachain_outbound_channels);
+					assert_eq!(v8.hrmp_sender_deposit                      , v9.hrmp_sender_deposit);
+					assert_eq!(v8.hrmp_recipient_deposit                   , v9.hrmp_recipient_deposit);
+					assert_eq!(v8.hrmp_channel_max_capacity                , v9.hrmp_channel_max_capacity);
+					assert_eq!(v8.hrmp_channel_max_total_size              , v9.hrmp_channel_max_total_size);
+					assert_eq!(v8.hrmp_max_parachain_inbound_channels      , v9.hrmp_max_parachain_inbound_channels);
+					assert_eq!(v8.hrmp_channel_max_message_size            , v9.hrmp_channel_max_message_size);
+					assert_eq!(v8.code_retention_period                    , v9.code_retention_period);
+					assert_eq!(v8.on_demand_cores                          , v9.on_demand_cores);
+					assert_eq!(v8.on_demand_retries                        , v9.on_demand_retries);
+					assert_eq!(v8.group_rotation_frequency                 , v9.group_rotation_frequency);
+					assert_eq!(v8.paras_availability_period                , v9.paras_availability_period);
+					assert_eq!(v8.scheduling_lookahead                     , v9.scheduling_lookahead);
+					assert_eq!(v8.max_validators_per_core                  , v9.max_validators_per_core);
+					assert_eq!(v8.max_validators                           , v9.max_validators);
+					assert_eq!(v8.dispute_period                           , v9.dispute_period);
+					assert_eq!(v8.no_show_slots                            , v9.no_show_slots);
+					assert_eq!(v8.n_delay_tranches                         , v9.n_delay_tranches);
+					assert_eq!(v8.zeroth_delay_tranche_width               , v9.zeroth_delay_tranche_width);
+					assert_eq!(v8.needed_approvals                         , v9.needed_approvals);
+					assert_eq!(v8.relay_vrf_modulo_samples                 , v9.relay_vrf_modulo_samples);
+					assert_eq!(v8.pvf_voting_ttl                           , v9.pvf_voting_ttl);
+					assert_eq!(v8.minimum_validation_upgrade_delay         , v9.minimum_validation_upgrade_delay);
+					assert_eq!(v8.async_backing_params.allowed_ancestry_len, v9.async_backing_params.allowed_ancestry_len);
+					assert_eq!(v8.async_backing_params.max_candidate_depth , v9.async_backing_params.max_candidate_depth);
+					assert_eq!(v8.executor_params						   , v9.executor_params);
+				    assert_eq!(v8.minimum_backing_votes					   , v9.minimum_backing_votes);
+				}; // ; makes this a statement. `rustfmt::skip` cannot be put on an expression.
+			}
+		});
+	}
+
+	// Test that migration doesn't panic in case there're no pending configurations upgrades in
+	// pallet's storage.
+	#[test]
+	fn test_migrate_to_v9_no_pending() {
+		let v8 = V8HostConfiguration::<primitives::BlockNumber>::default();
+
+		new_test_ext(Default::default()).execute_with(|| {
+			// Implant the v8 version in the state.
+			v8::ActiveConfig::<Test>::set(Some(v8));
+			// Ensure there're no pending configs.
+			v8::PendingConfigs::<Test>::set(None);
+
+			// Shouldn't fail.
+			migrate_to_v9::<Test>();
+		});
+	}
+}

polkadot/runtime/parachains/src/configuration/tests.rs

@@ -317,6 +317,7 @@ fn setting_pending_config_members() {
 			on_demand_fee_variability: Perbill::from_percent(3),
 			on_demand_target_queue_utilization: Perbill::from_percent(25),
 			on_demand_ttl: 5u32,
+			minimum_backing_votes: 5,
 		};
 
 		Configuration::set_validation_upgrade_cooldown(
@@ -467,6 +468,11 @@ fn setting_pending_config_members() {
 		.unwrap();
 		Configuration::set_pvf_voting_ttl(RuntimeOrigin::root(), new_config.pvf_voting_ttl)
 			.unwrap();
+		Configuration::set_minimum_backing_votes(
+			RuntimeOrigin::root(),
+			new_config.minimum_backing_votes,
+		)
+		.unwrap();
 
 		assert_eq!(PendingConfigs::<Test>::get(), vec![(shared::SESSION_DELAY, new_config)],);
 	})

polkadot/runtime/parachains/src/inclusion/mod.rs

@@ -36,11 +36,11 @@ use frame_system::pallet_prelude::*;
 use pallet_message_queue::OnQueueChanged;
 use parity_scale_codec::{Decode, Encode};
 use primitives::{
-	supermajority_threshold, well_known_keys, AvailabilityBitfield, BackedCandidate,
-	CandidateCommitments, CandidateDescriptor, CandidateHash, CandidateReceipt,
-	CommittedCandidateReceipt, CoreIndex, GroupIndex, Hash, HeadData, Id as ParaId,
-	SignedAvailabilityBitfields, SigningContext, UpwardMessage, ValidatorId, ValidatorIndex,
-	ValidityAttestation,
+	effective_minimum_backing_votes, supermajority_threshold, well_known_keys,
+	AvailabilityBitfield, BackedCandidate, CandidateCommitments, CandidateDescriptor,
+	CandidateHash, CandidateReceipt, CommittedCandidateReceipt, CoreIndex, GroupIndex, Hash,
+	HeadData, Id as ParaId, SignedAvailabilityBitfields, SigningContext, UpwardMessage,
+	ValidatorId, ValidatorIndex, ValidityAttestation,
 };
 use scale_info::TypeInfo;
 use sp_runtime::{traits::One, DispatchError, SaturatedConversion, Saturating};
@@ -199,17 +199,6 @@ impl<H> Default for ProcessedCandidates<H> {
 	}
 }
 
-/// Number of backing votes we need for a valid backing.
-///
-/// WARNING: This check has to be kept in sync with the node side checks.
-pub fn minimum_backing_votes(n_validators: usize) -> usize {
-	// For considerations on this value see:
-	// https://github.com/paritytech/polkadot/pull/1656#issuecomment-999734650
-	// and
-	// https://github.com/paritytech/polkadot/issues/4386
-	sp_std::cmp::min(n_validators, 2)
-}
-
 /// Reads the footprint of queues for a specific origin type.
 pub trait QueueFootprinter {
 	type Origin;
@@ -622,6 +611,7 @@ impl<T: Config> Pallet<T> {
 			return Ok(ProcessedCandidates::default())
 		}
 
+		let minimum_backing_votes = configuration::Pallet::<T>::config().minimum_backing_votes;
 		let validators = shared::Pallet::<T>::active_validator_keys();
 
 		// Collect candidate receipts with backers.
@@ -738,7 +728,11 @@ impl<T: Config> Pallet<T> {
 
 							match maybe_amount_validated {
 								Ok(amount_validated) => ensure!(
-									amount_validated >= minimum_backing_votes(group_vals.len()),
+									amount_validated >=
+										effective_minimum_backing_votes(
+											group_vals.len(),
+											minimum_backing_votes
+										),
 									Error::<T>::InsufficientBacking,
 								),
 								Err(()) => {

polkadot/runtime/parachains/src/inclusion/tests.rs

@@ -26,7 +26,10 @@ use crate::{
 	paras_inherent::DisputedBitfield,
 	shared::AllowedRelayParentsTracker,
 };
-use primitives::{SignedAvailabilityBitfields, UncheckedSignedAvailabilityBitfields};
+use primitives::{
+	effective_minimum_backing_votes, SignedAvailabilityBitfields,
+	UncheckedSignedAvailabilityBitfields,
+};
 
 use assert_matches::assert_matches;
 use frame_support::assert_noop;
@@ -120,11 +123,14 @@ pub(crate) fn back_candidate(
 	kind: BackingKind,
 ) -> BackedCandidate {
 	let mut validator_indices = bitvec::bitvec![u8, BitOrderLsb0; 0; group.len()];
-	let threshold = minimum_backing_votes(group.len());
+	let threshold = effective_minimum_backing_votes(
+		group.len(),
+		configuration::Pallet::<Test>::config().minimum_backing_votes,
+	);
 
 	let signing = match kind {
 		BackingKind::Unanimous => group.len(),
-		BackingKind::Threshold => threshold,
+		BackingKind::Threshold => threshold as usize,
 		BackingKind::Lacking => threshold.saturating_sub(1),
 	};
 
@@ -1609,7 +1615,10 @@ fn backing_works() {
 		);
 
 		let backers = {
-			let num_backers = minimum_backing_votes(group_validators(GroupIndex(0)).unwrap().len());
+			let num_backers = effective_minimum_backing_votes(
+				group_validators(GroupIndex(0)).unwrap().len(),
+				configuration::Pallet::<Test>::config().minimum_backing_votes,
+			);
 			backing_bitfield(&(0..num_backers).collect::<Vec<_>>())
 		};
 		assert_eq!(
@@ -1631,7 +1640,10 @@ fn backing_works() {
 		);
 
 		let backers = {
-			let num_backers = minimum_backing_votes(group_validators(GroupIndex(0)).unwrap().len());
+			let num_backers = effective_minimum_backing_votes(
+				group_validators(GroupIndex(0)).unwrap().len(),
+				configuration::Pallet::<Test>::config().minimum_backing_votes,
+			);
 			backing_bitfield(&(0..num_backers).map(|v| v + 2).collect::<Vec<_>>())
 		};
 		assert_eq!(
@@ -1765,7 +1777,10 @@ fn can_include_candidate_with_ok_code_upgrade() {
 		assert_eq!(occupied_cores, vec![(CoreIndex::from(0), chain_a)]);
 
 		let backers = {
-			let num_backers = minimum_backing_votes(group_validators(GroupIndex(0)).unwrap().len());
+			let num_backers = effective_minimum_backing_votes(
+				group_validators(GroupIndex(0)).unwrap().len(),
+				configuration::Pallet::<Test>::config().minimum_backing_votes,
+			);
 			backing_bitfield(&(0..num_backers).collect::<Vec<_>>())
 		};
 		assert_eq!(

polkadot/runtime/parachains/src/paras_inherent/tests.rs

@@ -948,8 +948,11 @@ fn default_header() -> primitives::Header {
 mod sanitizers {
 	use super::*;
 
-	use crate::inclusion::tests::{
-		back_candidate, collator_sign_candidate, BackingKind, TestCandidateBuilder,
+	use crate::{
+		inclusion::tests::{
+			back_candidate, collator_sign_candidate, BackingKind, TestCandidateBuilder,
+		},
+		mock::{new_test_ext, MockGenesisConfig},
 	};
 	use bitvec::order::Lsb0;
 	use primitives::{
@@ -1207,131 +1210,133 @@ mod sanitizers {
 
 	#[test]
 	fn candidates() {
-		const RELAY_PARENT_NUM: u32 = 3;
+		new_test_ext(MockGenesisConfig::default()).execute_with(|| {
+			const RELAY_PARENT_NUM: u32 = 3;
 
-		let header = default_header();
-		let relay_parent = header.hash();
-		let session_index = SessionIndex::from(0_u32);
+			let header = default_header();
+			let relay_parent = header.hash();
+			let session_index = SessionIndex::from(0_u32);
 
-		let keystore = LocalKeystore::in_memory();
-		let keystore = Arc::new(keystore) as KeystorePtr;
-		let signing_context = SigningContext { parent_hash: relay_parent, session_index };
+			let keystore = LocalKeystore::in_memory();
+			let keystore = Arc::new(keystore) as KeystorePtr;
+			let signing_context = SigningContext { parent_hash: relay_parent, session_index };
 
-		let validators = vec![
-			keyring::Sr25519Keyring::Alice,
-			keyring::Sr25519Keyring::Bob,
-			keyring::Sr25519Keyring::Charlie,
-			keyring::Sr25519Keyring::Dave,
-		];
-		for validator in validators.iter() {
-			Keystore::sr25519_generate_new(
-				&*keystore,
-				PARACHAIN_KEY_TYPE_ID,
-				Some(&validator.to_seed()),
-			)
-			.unwrap();
-		}
-
-		let has_concluded_invalid =
-			|_idx: usize, _backed_candidate: &BackedCandidate| -> bool { false };
-
-		let entry_ttl = 10_000;
-		let scheduled = (0_usize..2)
-			.into_iter()
-			.map(|idx| {
-				let core_idx = CoreIndex::from(idx as u32);
-				let ca = CoreAssignment {
-					paras_entry: ParasEntry::new(
-						Assignment::new(ParaId::from(1_u32 + idx as u32)),
-						entry_ttl,
-					),
-					core: core_idx,
-				};
-				ca
-			})
-			.collect::<Vec<_>>();
-
-		let group_validators = |group_index: GroupIndex| {
-			match group_index {
-				group_index if group_index == GroupIndex::from(0) => Some(vec![0, 1]),
-				group_index if group_index == GroupIndex::from(1) => Some(vec![2, 3]),
-				_ => panic!("Group index out of bounds for 2 parachains and 1 parathread core"),
+			let validators = vec![
+				keyring::Sr25519Keyring::Alice,
+				keyring::Sr25519Keyring::Bob,
+				keyring::Sr25519Keyring::Charlie,
+				keyring::Sr25519Keyring::Dave,
+			];
+			for validator in validators.iter() {
+				Keystore::sr25519_generate_new(
+					&*keystore,
+					PARACHAIN_KEY_TYPE_ID,
+					Some(&validator.to_seed()),
+				)
+				.unwrap();
 			}
-			.map(|m| m.into_iter().map(ValidatorIndex).collect::<Vec<_>>())
-		};
 
-		let backed_candidates = (0_usize..2)
-			.into_iter()
-			.map(|idx0| {
-				let idx1 = idx0 + 1;
-				let mut candidate = TestCandidateBuilder {
-					para_id: ParaId::from(idx1),
-					relay_parent,
-					pov_hash: Hash::repeat_byte(idx1 as u8),
-					persisted_validation_data_hash: [42u8; 32].into(),
-					hrmp_watermark: RELAY_PARENT_NUM,
-					..Default::default()
-				}
-				.build();
-
-				collator_sign_candidate(Sr25519Keyring::One, &mut candidate);
-
-				let backed = back_candidate(
-					candidate,
-					&validators,
-					group_validators(GroupIndex::from(idx0 as u32)).unwrap().as_ref(),
-					&keystore,
-					&signing_context,
-					BackingKind::Threshold,
-				);
-				backed
-			})
-			.collect::<Vec<_>>();
-
-		// happy path
-		assert_eq!(
-			sanitize_backed_candidates::<Test, _>(
-				backed_candidates.clone(),
-				has_concluded_invalid,
-				&scheduled
-			),
-			backed_candidates
-		);
-
-		// nothing is scheduled, so no paraids match, thus all backed candidates are skipped
-		{
-			let scheduled = &Vec::new();
-			assert!(sanitize_backed_candidates::<Test, _>(
-				backed_candidates.clone(),
-				has_concluded_invalid,
-				&scheduled
-			)
-			.is_empty());
-		}
-
-		// candidates that have concluded as invalid are filtered out
-		{
-			// mark every second one as concluded invalid
-			let set = {
-				let mut set = std::collections::HashSet::new();
-				for (idx, backed_candidate) in backed_candidates.iter().enumerate() {
-					if idx & 0x01 == 0 {
-						set.insert(backed_candidate.hash());
-					}
-				}
-				set
-			};
 			let has_concluded_invalid =
-				|_idx: usize, candidate: &BackedCandidate| set.contains(&candidate.hash());
+				|_idx: usize, _backed_candidate: &BackedCandidate| -> bool { false };
+
+			let entry_ttl = 10_000;
+			let scheduled = (0_usize..2)
+				.into_iter()
+				.map(|idx| {
+					let core_idx = CoreIndex::from(idx as u32);
+					let ca = CoreAssignment {
+						paras_entry: ParasEntry::new(
+							Assignment::new(ParaId::from(1_u32 + idx as u32)),
+							entry_ttl,
+						),
+						core: core_idx,
+					};
+					ca
+				})
+				.collect::<Vec<_>>();
+
+			let group_validators = |group_index: GroupIndex| {
+				match group_index {
+					group_index if group_index == GroupIndex::from(0) => Some(vec![0, 1]),
+					group_index if group_index == GroupIndex::from(1) => Some(vec![2, 3]),
+					_ => panic!("Group index out of bounds for 2 parachains and 1 parathread core"),
+				}
+				.map(|m| m.into_iter().map(ValidatorIndex).collect::<Vec<_>>())
+			};
+
+			let backed_candidates = (0_usize..2)
+				.into_iter()
+				.map(|idx0| {
+					let idx1 = idx0 + 1;
+					let mut candidate = TestCandidateBuilder {
+						para_id: ParaId::from(idx1),
+						relay_parent,
+						pov_hash: Hash::repeat_byte(idx1 as u8),
+						persisted_validation_data_hash: [42u8; 32].into(),
+						hrmp_watermark: RELAY_PARENT_NUM,
+						..Default::default()
+					}
+					.build();
+
+					collator_sign_candidate(Sr25519Keyring::One, &mut candidate);
+
+					let backed = back_candidate(
+						candidate,
+						&validators,
+						group_validators(GroupIndex::from(idx0 as u32)).unwrap().as_ref(),
+						&keystore,
+						&signing_context,
+						BackingKind::Threshold,
+					);
+					backed
+				})
+				.collect::<Vec<_>>();
+
+			// happy path
 			assert_eq!(
 				sanitize_backed_candidates::<Test, _>(
 					backed_candidates.clone(),
 					has_concluded_invalid,
 					&scheduled
-				)
-				.len(),
-				backed_candidates.len() / 2
+				),
+				backed_candidates
 			);
-		}
+
+			// nothing is scheduled, so no paraids match, thus all backed candidates are skipped
+			{
+				let scheduled = &Vec::new();
+				assert!(sanitize_backed_candidates::<Test, _>(
+					backed_candidates.clone(),
+					has_concluded_invalid,
+					&scheduled
+				)
+				.is_empty());
+			}
+
+			// candidates that have concluded as invalid are filtered out
+			{
+				// mark every second one as concluded invalid
+				let set = {
+					let mut set = std::collections::HashSet::new();
+					for (idx, backed_candidate) in backed_candidates.iter().enumerate() {
+						if idx & 0x01 == 0 {
+							set.insert(backed_candidate.hash());
+						}
+					}
+					set
+				};
+				let has_concluded_invalid =
+					|_idx: usize, candidate: &BackedCandidate| set.contains(&candidate.hash());
+				assert_eq!(
+					sanitize_backed_candidates::<Test, _>(
+						backed_candidates.clone(),
+						has_concluded_invalid,
+						&scheduled
+					)
+					.len(),
+					backed_candidates.len() / 2
+				);
+			}
+		});
 	}
 }

polkadot/runtime/parachains/src/runtime_api_impl/vstaging.rs

@@ -118,3 +118,8 @@ pub fn backing_state<T: initializer::Config>(
 pub fn async_backing_params<T: configuration::Config>() -> AsyncBackingParams {
 	<configuration::Pallet<T>>::config().async_backing_params
 }
+
+/// Return the min backing votes threshold from the configuration.
+pub fn minimum_backing_votes<T: initializer::Config>() -> u32 {
+	<configuration::Pallet<T>>::config().minimum_backing_votes
+}