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SubjectRe: [PATCH v2] iommu/vt-d: avoid unnecessory panic if iommu init fail in tboot system
From
Date
+Will

Please consider this patch for v5.10.

Best regards,
baolu

On 2020/11/10 15:19, Zhenzhong Duan wrote:
> "intel_iommu=off" command line is used to disable iommu but iommu is force
> enabled in a tboot system for security reason.
>
> However for better performance on high speed network device, a new option
> "intel_iommu=tboot_noforce" is introduced to disable the force on.
>
> 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 the code setting force_on and move intel_iommu_tboot_noforce
> from tboot code to intel iommu code.
>
> Fixes: 7304e8f28bb2 ("iommu/vt-d: Correctly disable Intel IOMMU force on")
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@gmail.com>
> ---
> v2: move ckeck of intel_iommu_tboot_noforce into iommu code per Baolu.
>
> arch/x86/kernel/tboot.c | 3 ---
> drivers/iommu/intel/iommu.c | 5 +++--
> include/linux/intel-iommu.h | 1 -
> 3 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
> index 992fb14..420be87 100644
> --- a/arch/x86/kernel/tboot.c
> +++ b/arch/x86/kernel/tboot.c
> @@ -514,9 +514,6 @@ int tboot_force_iommu(void)
> if (!tboot_enabled())
> return 0;
>
> - if (intel_iommu_tboot_noforce)
> - return 1;
> -
> if (no_iommu || swiotlb || dmar_disabled)
> pr_warn("Forcing Intel-IOMMU to enabled\n");
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 1b1ca63..4d9b298 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -179,7 +179,7 @@ static inline unsigned long virt_to_dma_pfn(void *p)
> * (used when kernel is launched w/ TXT)
> */
> static int force_on = 0;
> -int intel_iommu_tboot_noforce;
> +static int intel_iommu_tboot_noforce;
> static int no_platform_optin;
>
> #define ROOT_ENTRY_NR (VTD_PAGE_SIZE/sizeof(struct root_entry))
> @@ -4885,7 +4885,8 @@ int __init intel_iommu_init(void)
> * Intel IOMMU is required for a TXT/tboot launch or platform
> * opt in, so enforce that.
> */
> - force_on = tboot_force_iommu() || platform_optin_force_iommu();
> + force_on = (!intel_iommu_tboot_noforce && tboot_force_iommu()) ||
> + platform_optin_force_iommu();
>
> if (iommu_init_mempool()) {
> if (force_on)
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index fbf5b3e..d956987 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -798,7 +798,6 @@ struct context_entry *iommu_context_addr(struct intel_iommu *iommu, u8 bus,
> extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
> extern int dmar_disabled;
> extern int intel_iommu_enabled;
> -extern int intel_iommu_tboot_noforce;
> extern int intel_iommu_gfx_mapped;
> #else
> static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
>

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