From: Joerg Roedel jroedel@suse.de
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: 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iommu/amd/init.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -20,6 +20,7 @@ #include <linux/export.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> @@ -833,6 +834,7 @@ static int iommu_ga_log_enable(struct am status = readl(iommu->mmio_base + MMIO_STATUS_OFFSET); if (status & (MMIO_STATUS_GALOG_RUN_MASK)) break; + udelay(10); }
if (WARN_ON(i >= LOOP_TIMEOUT))