On Fri, Jan 31, 2025, Ashish Kalra wrote:
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
>
> This patch fixes the current SNP host enabling code and effectively SNP
^^^^^^^^^^
> ---
> drivers/iommu/amd/init.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index c5cd92edada0..ee887aa4442f 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -3194,7 +3194,7 @@ static bool __init detect_ivrs(void)
> return true;
> }
>
> -static void iommu_snp_enable(void)
> +static __init void iommu_snp_enable(void)
If you're feeling nitpicky, adding "__init" could be done in a separate patch.
> {
> #ifdef CONFIG_KVM_AMD_SEV
> if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
> @@ -3219,6 +3219,11 @@ static void iommu_snp_enable(void)
> goto disable_snp;
> }
>
> + if (snp_rmptable_init()) {
> + pr_warn("SNP: RMP initialization failed, SNP cannot be supported.\n");
> + goto disable_snp;
> + }
> +
> pr_info("IOMMU SNP support enabled.\n");
> return;
>
> @@ -3426,18 +3431,23 @@ void __init amd_iommu_detect(void)
> int ret;
>
> if (no_iommu || (iommu_detected && !gart_iommu_aperture))
> - return;
> + goto disable_snp;
>
> if (!amd_iommu_sme_check())
> - return;
> + goto disable_snp;
>
> ret = iommu_go_to_state(IOMMU_IVRS_DETECTED);
> if (ret)
> - return;
> + goto disable_snp;
This handles initial failure, but it won't handle the case where amd_iommu_prepare()
fails, as the iommu_go_to_state() call from amd_iommu_enable() will get
short-circuited. I don't see any pleasant options. Maybe this?
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index c5cd92edada0..436e47f13f8f 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3318,6 +3318,8 @@ static int __init iommu_go_to_state(enum iommu_init_state state)
ret = state_next();
}
+ if (ret && !amd_iommu_snp_en && cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+ cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
return ret;
}
Somewhat of a side topic, what happens if the RMP is fully configured and _then_
IOMMU initialization fails? I.e. if amd_iommu_init_pci() or amd_iommu_enable_interrupts()
fails? Is that even survivable?
>
> amd_iommu_detected = true;
> iommu_detected = 1;
> x86_init.iommu.iommu_init = amd_iommu_init;
> + return;
> +
> +disable_snp:
> + if (cc_platform_has(CC_ATTR_HOST_SEV_SNP))
> + cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
> }
>
> /****************************************************************************
> --
> 2.34.1
>
