Re: [PATCH v1 04/26] x86/sev: Add the host SEV-SNP initialization support

[Borislav Petkov]

On Sat, Dec 30, 2023 at 10:19:32AM -0600, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@xxxxxxx>
> 
> The memory integrity guarantees of SEV-SNP are enforced through a new
> structure called the Reverse Map Table (RMP). The RMP is a single data
> structure shared across the system that contains one entry for every 4K
> page of DRAM that may be used by SEV-SNP VMs. APM2 section 15.36 details
> a number of steps needed to detect/enable SEV-SNP and RMP table support
> on the host:
> 
>  - Detect SEV-SNP support based on CPUID bit
>  - Initialize the RMP table memory reported by the RMP base/end MSR
>    registers and configure IOMMU to be compatible with RMP access
>    restrictions
>  - Set the MtrrFixDramModEn bit in SYSCFG MSR
>  - Set the SecureNestedPagingEn and VMPLEn bits in the SYSCFG MSR
>  - Configure IOMMU
> 
> RMP table entry format is non-architectural and it can vary by
> processor. It is defined by the PPR. Restrict SNP support to CPU
> models/families which are compatible with the current RMP table entry
> format to guard against any undefined behavior when running on other
> system types. Future models/support will handle this through an
> architectural mechanism to allow for broader compatibility.
> 
> SNP host code depends on CONFIG_KVM_AMD_SEV config flag, which may be
> enabled even when CONFIG_AMD_MEM_ENCRYPT isn't set, so update the
> SNP-specific IOMMU helpers used here to rely on CONFIG_KVM_AMD_SEV
> instead of CONFIG_AMD_MEM_ENCRYPT.

Small fixups to the commit message:

    The memory integrity guarantees of SEV-SNP are enforced through a new
    structure called the Reverse Map Table (RMP). The RMP is a single data
    structure shared across the system that contains one entry for every 4K
    page of DRAM that may be used by SEV-SNP VMs. The APM v2 section on
    Secure Nested Paging (SEV-SNP) details a number of steps needed to
    detect/enable SEV-SNP and RMP table support on the host:
    
     - Detect SEV-SNP support based on CPUID bit
     - Initialize the RMP table memory reported by the RMP base/end MSR
       registers and configure IOMMU to be compatible with RMP access
       restrictions
     - Set the MtrrFixDramModEn bit in SYSCFG MSR
     - Set the SecureNestedPagingEn and VMPLEn bits in the SYSCFG MSR
     - Configure IOMMU
    
    The RMP table entry format is non-architectural and it can vary by
    processor. It is defined by the PPR document for each respective CPU
    family. Restrict SNP support to CPU models/families which are compatible
    with the current RMP table entry format to guard against any undefined
    behavior when running on other system types. Future models/support will
    handle this through an architectural mechanism to allow for broader
    compatibility.
    
    The SNP host code depends on CONFIG_KVM_AMD_SEV config flag which may
    be enabled even when CONFIG_AMD_MEM_ENCRYPT isn't set, so update the
    SNP-specific IOMMU helpers used here to rely on CONFIG_KVM_AMD_SEV
    instead of CONFIG_AMD_MEM_ENCRYPT.

> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index f1bd7b91b3c6..15ce1269f270 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -599,6 +599,8 @@
>  #define MSR_AMD64_SEV_ENABLED		BIT_ULL(MSR_AMD64_SEV_ENABLED_BIT)
>  #define MSR_AMD64_SEV_ES_ENABLED	BIT_ULL(MSR_AMD64_SEV_ES_ENABLED_BIT)
>  #define MSR_AMD64_SEV_SNP_ENABLED	BIT_ULL(MSR_AMD64_SEV_SNP_ENABLED_BIT)
> +#define MSR_AMD64_RMP_BASE		0xc0010132
> +#define MSR_AMD64_RMP_END		0xc0010133
>  
>  /* SNP feature bits enabled by the hypervisor */
>  #define MSR_AMD64_SNP_VTOM			BIT_ULL(3)
> @@ -709,7 +711,14 @@
>  #define MSR_K8_TOP_MEM2			0xc001001d
>  #define MSR_AMD64_SYSCFG		0xc0010010
>  #define MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT	23
> -#define MSR_AMD64_SYSCFG_MEM_ENCRYPT	BIT_ULL(MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT)
> +#define MSR_AMD64_SYSCFG_MEM_ENCRYPT		BIT_ULL(MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT)
> +#define MSR_AMD64_SYSCFG_SNP_EN_BIT		24
> +#define MSR_AMD64_SYSCFG_SNP_EN		BIT_ULL(MSR_AMD64_SYSCFG_SNP_EN_BIT)
> +#define MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT	25
> +#define MSR_AMD64_SYSCFG_SNP_VMPL_EN		BIT_ULL(MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT)
> +#define MSR_AMD64_SYSCFG_MFDM_BIT		19
> +#define MSR_AMD64_SYSCFG_MFDM			BIT_ULL(MSR_AMD64_SYSCFG_MFDM_BIT)
> +

Fix the vertical alignment:

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 15ce1269f270..f482bc6a5ae7 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -710,14 +710,14 @@
 #define MSR_K8_TOP_MEM1			0xc001001a
 #define MSR_K8_TOP_MEM2			0xc001001d
 #define MSR_AMD64_SYSCFG		0xc0010010
-#define MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT	23
-#define MSR_AMD64_SYSCFG_MEM_ENCRYPT		BIT_ULL(MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT)
-#define MSR_AMD64_SYSCFG_SNP_EN_BIT		24
+#define MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT 23
+#define MSR_AMD64_SYSCFG_MEM_ENCRYPT	BIT_ULL(MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT)
+#define MSR_AMD64_SYSCFG_SNP_EN_BIT	24
 #define MSR_AMD64_SYSCFG_SNP_EN		BIT_ULL(MSR_AMD64_SYSCFG_SNP_EN_BIT)
-#define MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT	25
-#define MSR_AMD64_SYSCFG_SNP_VMPL_EN		BIT_ULL(MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT)
-#define MSR_AMD64_SYSCFG_MFDM_BIT		19
-#define MSR_AMD64_SYSCFG_MFDM			BIT_ULL(MSR_AMD64_SYSCFG_MFDM_BIT)
+#define MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT 25
+#define MSR_AMD64_SYSCFG_SNP_VMPL_EN	BIT_ULL(MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT)
+#define MSR_AMD64_SYSCFG_MFDM_BIT	19
+#define MSR_AMD64_SYSCFG_MFDM		BIT_ULL(MSR_AMD64_SYSCFG_MFDM_BIT)
 
 #define MSR_K8_INT_PENDING_MSG		0xc0010055
 /* C1E active bits in int pending message */

-- 
Regards/Gruss,
    Boris.

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