From 9b45a7738eec52bf0f5d8d3d54e822962781c5f2 Mon Sep 17 00:00:00 2001 From: Joerg Roedel 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 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 dc338ac..b10fb52 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -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)) -- 2.7.4