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SubjectRe: [PATCH] iommu/amd: Fix loop timeout issue in iommu_ga_log_enable()
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On 31/01/2022 16:17, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> 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.
>
> Fixes: 8bda0cfbdc1a ("iommu/amd: Detect and initialize guest vAPIC log")
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> drivers/iommu/amd/init.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index dc338acf3338..d2e09d53851f 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -834,6 +834,7 @@ 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(1);

Maybe readl_relaxed_poll_timeout_atomic() could be used instead

Thanks,
John

> }
>
> if (WARN_ON(i >= LOOP_TIMEOUT))
>

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