Hi Ashish,
[Sorry. I didn't see this series and responded to v2].
On 2/4/2025 3:26 AM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
>
> Fix issues with enabling SNP host support and effectively SNP support
> which is broken with respect to the KVM module being built-in.
>
> SNP host support is enabled in snp_rmptable_init() which is invoked as
> device_initcall(). SNP check on IOMMU is done during IOMMU PCI init
> (IOMMU_PCI_INIT stage). And for that reason snp_rmptable_init() is
> currently invoked via device_initcall() and cannot be invoked via
> subsys_initcall() as core IOMMU subsystem gets initialized via
> subsys_initcall().
>
> Now, if kvm_amd module is built-in, it gets initialized before SNP host
> support is enabled in snp_rmptable_init() :
>
> [ 10.131811] kvm_amd: TSC scaling supported
> [ 10.136384] kvm_amd: Nested Virtualization enabled
> [ 10.141734] kvm_amd: Nested Paging enabled
> [ 10.146304] kvm_amd: LBR virtualization supported
> [ 10.151557] kvm_amd: SEV enabled (ASIDs 100 - 509)
> [ 10.156905] kvm_amd: SEV-ES enabled (ASIDs 1 - 99)
> [ 10.162256] kvm_amd: SEV-SNP enabled (ASIDs 1 - 99)
> [ 10.171508] kvm_amd: Virtual VMLOAD VMSAVE supported
> [ 10.177052] kvm_amd: Virtual GIF supported
> ...
> ...
.../...
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index c5cd92edada0..4bcb474e2252 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)
> {
> #ifdef CONFIG_KVM_AMD_SEV
> if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
> @@ -3219,6 +3219,14 @@ static void iommu_snp_enable(void)
> goto disable_snp;
> }
>
> + /*
> + * Enable host SNP support once SNP support is checked on IOMMU.
> + */
> + 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;
>
> @@ -3318,6 +3326,9 @@ 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))
I think we should clear when `amd_iommu_snp_en` is true. May be below check is
enough?
if (ret && amd_iommu_snp_en)
-Vasant
