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SubjectRe: [PATCH] iommu/vt-d: avoid unnecessory panic if iommu init fail in tboot
+intel iommu maintainers,

Can anyone help review this patch? Thanks

Zhenzhong

On Wed, Nov 4, 2020 at 4:15 PM Zhenzhong Duan <zhenzhong.duan@gmail.com> wrote:
>
> "intel_iommu=off" command line is used to disable iommu and iommu is force
> enabled in a tboot system. Meanwhile "intel_iommu=tboot_noforce,off"
> could be used to force disable iommu in tboot for better performance.
>
> By default kernel should panic if iommu init fail in tboot for security
> reason, but it's unnecessory if we use "intel_iommu=tboot_noforce,off".
>
> Fix it by return 0 in tboot_force_iommu() so that force_on is not set.
>
> Fixes: 7304e8f28bb2 ("iommu/vt-d: Correctly disable Intel IOMMU force on")
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@gmail.com>
> ---
> arch/x86/kernel/tboot.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
> index 992fb1415c0f..9fd4d162b331 100644
> --- a/arch/x86/kernel/tboot.c
> +++ b/arch/x86/kernel/tboot.c
> @@ -511,12 +511,9 @@ struct acpi_table_header *tboot_get_dmar_table(struct acpi_table_header *dmar_tb
>
> int tboot_force_iommu(void)
> {
> - if (!tboot_enabled())
> + if (!tboot_enabled() || intel_iommu_tboot_noforce)
> return 0;
>
> - if (intel_iommu_tboot_noforce)
> - return 1;
> -
> if (no_iommu || swiotlb || dmar_disabled)
> pr_warn("Forcing Intel-IOMMU to enabled\n");
>
> --
> 2.25.1
>

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