Commit 6e0498e2 authored Feb 04, 2022 by Joerg Roedel Committed by Greg Kroah-Hartman Feb 08, 2022

iommu/amd: Fix loop timeout issue in iommu_ga_log_enable()

commit 9b45a7738eec52bf0f5d8d3d54e822962781c5f2 upstream.

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: 8bda0cfb ("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

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 5c43d46d

drivers/iommu/amd_iommu_init.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,7 @@
		#include <linux/iommu.h>
		#include <linux/kmemleak.h>
		#include <linux/mem_encrypt.h>
		#include <linux/iopoll.h>
		#include <asm/pci-direct.h>
		#include <asm/iommu.h>
		#include <asm/apic.h>
		@@ -759,6 +760,7 @@ 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 (i >= LOOP_TIMEOUT)