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

Borislav Petkov
2024-01-04T11:17:57Z

On Sat, Dec 30, 2023 at 10:19:32AM -0600, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@amd.com>
>
> 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.