Commit f0eb154c authored by Marc Zyngier's avatar Marc Zyngier Committed by Thomas Gleixner
Browse files

irqchip/gic-v4: Substitute vmovp_lock for a per-VM lock 



vmovp_lock is abused in a number of cases to serialise updates
to vlpi_count[] and deal with map/unmap of a VM to ITSs.

Instead, provide a per-VM lock and revisit the use of vlpi_count[]
so that it is always wrapped in this per-VM vmapp_lock.

This reduces the potential contention on a concurrent VMOVP command,
and paves the way for subsequent VPE locking that holding vmovp_lock
actively prevents due to the lock ordering.

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarNianyao Tang <tangnianyao@huawei.com>
Link: https://lore.kernel.org/r/20240705093155.871070-3-maz@kernel.org
parent 7d2c2048

drivers/irqchip/irq-gic-v3-its.c

+12 −15
Original line number Diff line number Diff line
@@ -1317,7 +1317,6 @@ static void its_send_vmovp(struct its_vpe *vpe) 
{

	struct its_cmd_desc desc = {};

	struct its_node *its;

	unsigned long flags;

	int col_id = vpe->col_idx;



	desc.its_vmovp_cmd.vpe = vpe;
@@ -1329,6 +1328,12 @@ static void its_send_vmovp(struct its_vpe *vpe) 
		return;

	}



	/*

	 * Protect against concurrent updates of the mapping state on

	 * individual VMs.

	 */

	guard(raw_spinlock_irqsave)(&vpe->its_vm->vmapp_lock);



	/*

	 * Yet another marvel of the architecture. If using the

	 * its_list "feature", we need to make sure that all ITSs
@@ -1337,8 +1342,7 @@ static void its_send_vmovp(struct its_vpe *vpe) 
	 *

	 * Wall <-- Head.

	 */

	raw_spin_lock_irqsave(&vmovp_lock, flags);



	guard(raw_spinlock)(&vmovp_lock);

	desc.its_vmovp_cmd.seq_num = vmovp_seq_num++;

	desc.its_vmovp_cmd.its_list = get_its_list(vpe->its_vm);
@@ -1353,8 +1357,6 @@ static void its_send_vmovp(struct its_vpe *vpe) 
		desc.its_vmovp_cmd.col = &its->collections[col_id];

		its_send_single_vcommand(its, its_build_vmovp_cmd, &desc);

	}



	raw_spin_unlock_irqrestore(&vmovp_lock, flags);

}



static void its_send_vinvall(struct its_node *its, struct its_vpe *vpe)
@@ -1791,12 +1793,10 @@ static bool gic_requires_eager_mapping(void) 


static void its_map_vm(struct its_node *its, struct its_vm *vm)

{

	unsigned long flags;



	if (gic_requires_eager_mapping())

		return;



	raw_spin_lock_irqsave(&vmovp_lock, flags);

	guard(raw_spinlock_irqsave)(&vm->vmapp_lock);



	/*

	 * If the VM wasn't mapped yet, iterate over the vpes and get
@@ -1814,19 +1814,15 @@ static void its_map_vm(struct its_node *its, struct its_vm *vm) 
			its_send_vinvall(its, vpe);

		}

	}



	raw_spin_unlock_irqrestore(&vmovp_lock, flags);

}



static void its_unmap_vm(struct its_node *its, struct its_vm *vm)

{

	unsigned long flags;



	/* Not using the ITS list? Everything is always mapped. */

	if (gic_requires_eager_mapping())

		return;



	raw_spin_lock_irqsave(&vmovp_lock, flags);

	guard(raw_spinlock_irqsave)(&vm->vmapp_lock);



	if (!--vm->vlpi_count[its->list_nr]) {

		int i;
@@ -1834,8 +1830,6 @@ static void its_unmap_vm(struct its_node *its, struct its_vm *vm) 
		for (i = 0; i < vm->nr_vpes; i++)

			its_send_vmapp(its, vm->vpes[i], false);

	}



	raw_spin_unlock_irqrestore(&vmovp_lock, flags);

}



static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
@@ -3942,6 +3936,8 @@ static void its_vpe_invall(struct its_vpe *vpe) 
{

	struct its_node *its;



	guard(raw_spinlock_irqsave)(&vpe->its_vm->vmapp_lock);



	list_for_each_entry(its, &its_nodes, entry) {

		if (!is_v4(its))

			continue;
@@ -4547,6 +4543,7 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq 
	vm->db_lpi_base = base;

	vm->nr_db_lpis = nr_ids;

	vm->vprop_page = vprop_page;

	raw_spin_lock_init(&vm->vmapp_lock);



	if (gic_rdists->has_rvpeid)

		irqchip = &its_vpe_4_1_irq_chip;

include/linux/irqchip/arm-gic-v4.h

+8 −0
Original line number Diff line number Diff line
@@ -25,6 +25,14 @@ struct its_vm { 
	irq_hw_number_t		db_lpi_base;

	unsigned long		*db_bitmap;

	int			nr_db_lpis;

	/*

	 * Ensures mutual exclusion between updates to vlpi_count[]

	 * and map/unmap when using the ITSList mechanism.

	 *

	 * The lock order for any sequence involving the ITSList is

	 * vmapp_lock -> vpe_lock ->vmovp_lock.

	 */

	raw_spinlock_t		vmapp_lock;

	u32			vlpi_count[GICv4_ITS_LIST_MAX];

};