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: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nianyao Tang <tangnianyao@huawei.com>
Link: https://lore.kernel.org/r/20240705093155.871070-3-maz@kernel.org

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 387ac5a31d1ddb8c0326be8a964e5073df6f8ec4..215c7ab74e3ac9bf4eac05a9f6fe5467400413a3 100644 (file)
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -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;

diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
index 2c63375bbd43f41d3c5019ab4f4f3583196b522f..ecabed6d3307528dd34c3fb2e02642d20771fc55 100644 (file)
--- a/include/linux/irqchip/arm-gic-v4.h
+++ b/include/linux/irqchip/arm-gic-v4.h
@@ -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];
 };