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From 9b45a7738eec52bf0f5d8d3d54e822962781c5f2 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@suse.de>
Date: Fri, 4 Feb 2022 12:55:37 +0100
Subject: [PATCH] iommu/amd: Fix loop timeout issue in iommu_ga_log_enable()
The polling loop for the register change in iommu_ga_log_enable() needs
to have a udelay() in it. Otherwise the CPU might be faster than the
IOMMU hardware and wrongly trigger the WARN_ON() further down the code
stream. Use a 10us for udelay(), has there is some hardware where
activation of the GA log can take more than a 100ms.
A future optimization should move the activation check of the GA log
to the point where it gets used for the first time. But that is a
bigger change and not suitable for a fix.
Fixes: 8bda0cfbdc1a ("iommu/amd: Detect and initialize guest vAPIC log")
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20220204115537.3894-1-joro@8bytes.org
---
drivers/iommu/amd/init.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index dc338acf3338..b10fb52ea442 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -21,6 +21,7 @@
#include <linux/export.h>
#include <linux/kmemleak.h>
#include <linux/cc_platform.h>
+#include <linux/iopoll.h>
#include <asm/pci-direct.h>
#include <asm/iommu.h>
#include <asm/apic.h>
@@ -834,6 +835,7 @@ static int iommu_ga_log_enable(struct amd_iommu *iommu)
status = readl(iommu->mmio_base + MMIO_STATUS_OFFSET);
if (status & (MMIO_STATUS_GALOG_RUN_MASK))
break;
+ udelay(10);
}
if (WARN_ON(i >= LOOP_TIMEOUT))
--
2.35.1
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