linux-kernel - [tip: locking/core] x86,amd_iommu: Replace cmpxchg

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Message-ID: <168595097042.404.1105917513854333768.tip-bot2@tip-bot2>
Date:   Mon, 05 Jun 2023 07:42:50 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Vasant Hegde <vasant.hegde@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] x86,amd_iommu: Replace cmpxchg_double()

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     0a0a6800b02489c1288f963ad290b6a4876a2cc8
Gitweb:        https://git.kernel.org/tip/0a0a6800b02489c1288f963ad290b6a4876a2cc8
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Wed, 31 May 2023 15:08:41 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 05 Jun 2023 09:36:38 +02:00

x86,amd_iommu: Replace cmpxchg_double()

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Mark Rutland <mark.rutland@....com>
Tested-by: Vasant Hegde <vasant.hegde@....com>
Tested-by: Mark Rutland <mark.rutland@....com>
Link: https://lore.kernel.org/r/20230531132323.788955257@infradead.org
---
 drivers/iommu/amd/amd_iommu_types.h |  9 +++++++--
 drivers/iommu/amd/iommu.c           | 10 ++++------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 2ddbda3..ab8aa8f 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -986,8 +986,13 @@ union irte_ga_hi {
 };
 
 struct irte_ga {
-	union irte_ga_lo lo;
-	union irte_ga_hi hi;
+	union {
+		struct {
+			union irte_ga_lo lo;
+			union irte_ga_hi hi;
+		};
+		u128 irte;
+	};
 };
 
 struct irq_2_irte {
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 4a31464..1e9f85e 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3003,10 +3003,10 @@ out:
 static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
 			  struct irte_ga *irte, struct amd_ir_data *data)
 {
-	bool ret;
 	struct irq_remap_table *table;
-	unsigned long flags;
 	struct irte_ga *entry;
+	unsigned long flags;
+	u128 old;
 
 	table = get_irq_table(iommu, devid);
 	if (!table)
@@ -3017,16 +3017,14 @@ static int modify_irte_ga(struct amd_iommu *iommu, u16 devid, int index,
 	entry = (struct irte_ga *)table->table;
 	entry = &entry[index];
 
-	ret = cmpxchg_double(&entry->lo.val, &entry->hi.val,
-			     entry->lo.val, entry->hi.val,
-			     irte->lo.val, irte->hi.val);
 	/*
 	 * We use cmpxchg16 to atomically update the 128-bit IRTE,
 	 * and it cannot be updated by the hardware or other processors
 	 * behind us, so the return value of cmpxchg16 should be the
 	 * same as the old value.
 	 */
-	WARN_ON(!ret);
+	old = entry->irte;
+	WARN_ON(!try_cmpxchg128(&entry->irte, &old, irte->irte));
 
 	if (data)
 		data->ref = entry;