linux-kernel - [PATCH v2 5/5] iommu/amd: Improving Interrupt Remapping Table Invalidation

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Date:   Thu, 18 May 2023 20:55:29 -0400
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>
CC:     <joro@...tes.org>, <joao.m.martins@...cle.com>,
        <alejandro.j.jimenez@...cle.com>, <boris.ostrovsky@...cle.com>,
        <jon.grimm@....com>, <santosh.shukla@....com>,
        <vasant.hegde@....com>, <kishon.vijayabraham@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v2 5/5] iommu/amd: Improving Interrupt Remapping Table Invalidation

Invalidating Interrupt Remapping Table (IRT) requires, the AMD IOMMU driver
to issue INVALIDATE_INTERRUPT_TABLE and COMPLETION_WAIT commands.
Currently, the driver issues the two commands separately, which requires
calling raw_spin_lock_irqsave() twice. In addition, the COMPLETION_WAIT
could potentially be interleaved with other commands causing delay of
the COMPLETION_WAIT command.

Therefore, combine issuing of the two commands in one spin-lock, and
changing struct amd_iommu.cmd_sem_val to use atomic64 to minimize
locking.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/amd_iommu_types.h |  2 +-
 drivers/iommu/amd/init.c            |  2 +-
 drivers/iommu/amd/iommu.c           | 27 ++++++++++++++++++++++-----
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 486a052e37ca..2fa65da2a9a5 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -744,7 +744,7 @@ struct amd_iommu {
 
 	u32 flags;
 	volatile u64 *cmd_sem;
-	u64 cmd_sem_val;
+	atomic64_t cmd_sem_val;
 
 #ifdef CONFIG_AMD_IOMMU_DEBUGFS
 	/* DebugFS Info */
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index fc0392d706db..16737819f79a 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -1750,7 +1750,7 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h,
 	iommu->pci_seg = pci_seg;
 
 	raw_spin_lock_init(&iommu->lock);
-	iommu->cmd_sem_val = 0;
+	atomic64_set(&iommu->cmd_sem_val, 0);
 
 	/* Add IOMMU to internal data structures */
 	list_add_tail(&iommu->list, &amd_iommu_list);
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 51c2b018433d..57ae4a8072d3 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -1182,11 +1182,11 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
 	if (!iommu->need_sync)
 		return 0;
 
-	raw_spin_lock_irqsave(&iommu->lock, flags);
-
-	data = ++iommu->cmd_sem_val;
+	data = atomic64_add_return(1, &iommu->cmd_sem_val);
 	build_completion_wait(&cmd, iommu, data);
 
+	raw_spin_lock_irqsave(&iommu->lock, flags);
+
 	ret = __iommu_queue_command_sync(iommu, &cmd, false);
 	if (ret)
 		goto out_unlock;
@@ -1284,11 +1284,28 @@ static void amd_iommu_flush_irt_all(struct amd_iommu *iommu)
 
 static void iommu_flush_irt_and_complete(struct amd_iommu *iommu, u16 devid)
 {
+	int ret;
+	u64 data;
+	unsigned long flags;
+	struct iommu_cmd cmd, cmd2;
+
 	if (iommu->irtcachedis_enabled)
 		return;
 
-	iommu_flush_irt(iommu, devid);
-	iommu_completion_wait(iommu);
+	build_inv_irt(&cmd, devid);
+	data = atomic64_add_return(1, &iommu->cmd_sem_val);
+	build_completion_wait(&cmd2, iommu, data);
+
+	raw_spin_lock_irqsave(&iommu->lock, flags);
+	ret = __iommu_queue_command_sync(iommu, &cmd, true);
+	if (ret)
+		goto out;
+	ret = __iommu_queue_command_sync(iommu, &cmd2, false);
+	if (ret)
+		goto out;
+	wait_on_sem(iommu, data);
+out:
+	raw_spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
 void iommu_flush_all_caches(struct amd_iommu *iommu)
-- 
2.31.1