linux-kernel - [PATCH v2 5/5] iommu/amd: Use 128-bit cmpxchg in set_dte_irq

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Message-ID: <20240829180726.5022-6-suravee.suthikulpanit@amd.com>
Date: Thu, 29 Aug 2024 18:07:26 +0000
From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To: <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>
CC: <joro@...tes.org>, <robin.murphy@....com>, <vasant.hegde@....com>,
	<ubizjak@...il.com>, <jgg@...dia.com>, <jon.grimm@....com>,
	<santosh.shukla@....com>, <pandoh@...gle.com>, <kumaranand@...gle.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v2 5/5] iommu/amd: Use 128-bit cmpxchg in set_dte_irq_entry()

Interrupt-remapping-related fields are in the top 128-bit of the Device
Table Entry (DTE), which should be updated using 128-bit write based on the
AMD I/O Virtualization Techonology (IOMMU) Specification.

Therefore, modify set_dte_irq_entry() to use 128-bit cmpxchg. Also, use
struct dev_data->dte_sem to synchronize DTE access.

Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/iommu.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index a24986c2478b..4eb53bd40487 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3020,17 +3020,24 @@ static void iommu_flush_irt_and_complete(struct amd_iommu *iommu, u16 devid)
 static void set_dte_irq_entry(struct amd_iommu *iommu, u16 devid,
 			      struct irq_remap_table *table)
 {
-	u64 dte;
-	struct dev_table_entry *dev_table = get_dev_table(iommu);
+	u128 new, old;
+	struct dev_table_entry *dte = &get_dev_table(iommu)[devid];
+	struct iommu_dev_data *dev_data = search_dev_data(iommu, devid);
+
+	if (dev_data)
+		down_write(&dev_data->dte_sem);
+
+	old = new = dte->data128[1];
+	new &= ~DTE_IRQ_PHYS_ADDR_MASK;
+	new |= iommu_virt_to_phys(table->table);
+	new |= DTE_IRQ_REMAP_INTCTL;
+	new |= DTE_INTTABLEN;
+	new |= DTE_IRQ_REMAP_ENABLE;
 
-	dte	= dev_table[devid].data[2];
-	dte	&= ~DTE_IRQ_PHYS_ADDR_MASK;
-	dte	|= iommu_virt_to_phys(table->table);
-	dte	|= DTE_IRQ_REMAP_INTCTL;
-	dte	|= DTE_INTTABLEN;
-	dte	|= DTE_IRQ_REMAP_ENABLE;
+	WARN_ON(!try_cmpxchg128(&dte->data128[1], &old, new));
 
-	dev_table[devid].data[2] = dte;
+	if (dev_data)
+		up_write(&dev_data->dte_sem);
 }
 
 static struct irq_remap_table *get_irq_table(struct amd_iommu *iommu, u16 devid)
-- 
2.34.1