On 11/25/21 7:12 AM, qi zhou wrote:
From 5b10265fa5c7b5ca728b4f18488089de6535ed28 Mon Sep 17 00:00:00 2001 From: Qi Zhou <atm...@outlook.com> Date: Thu, 25 Nov 2021 20:25:55 +0800 Subject: [PATCH] OvmfPkg/MemEncryptSevLib: check CPUID when read msr during PEI phaseTested on Intel Platform, It is like 'SEV-ES work area' can be modified by os(Windows etc), and will not restored on reboot, the SevEsWorkArea->EncryptionMask may have a random value after reboot. then it may casue fail on reboot. The msr bits already cached by mSevStatusChecked, there is no need to try cache again in PEI phase. Signed-off-by: Qi Zhou <atm...@outlook.com> --- .../PeiMemEncryptSevLibInternal.c | 55 +++++++------------ 1 file changed, 19 insertions(+), 36 deletions(-) diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c index e2fd109d12..0819f50669 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c @@ -38,49 +38,32 @@ InternalMemEncryptSevStatus ( UINT32 RegEax; MSR_SEV_STATUS_REGISTER Msr; CPUID_MEMORY_ENCRYPTION_INFO_EAX Eax; - BOOLEAN ReadSevMsr; - SEC_SEV_ES_WORK_AREA *SevEsWorkArea;- ReadSevMsr = FALSE;- - SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *) FixedPcdGet32 (PcdSevEsWorkAreaBase); - if (SevEsWorkArea != NULL && SevEsWorkArea->EncryptionMask != 0) { - // - // The MSR has been read before, so it is safe to read it again and avoid - // having to validate the CPUID information. + // + // Check if memory encryption leaf exist + // + AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL); + if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
This now defeats the purpose of the workarea the already validated CPUID information. This CPUID information will now require validating.
Wouldn't the best thing be to clear the workarea in the early boot code? Thanks, Tom
// - ReadSevMsr = TRUE; - } else { + // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported) // - // Check if memory encryption leaf exist - // - AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL); - if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) { + AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL); + + if (Eax.Bits.SevBit) { // - // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported) + // Check MSR_0xC0010131 Bit 0 (Sev Enabled) // - AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL); - - if (Eax.Bits.SevBit) { - ReadSevMsr = TRUE; + Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS); + if (Msr.Bits.SevBit) { + mSevStatus = TRUE; } - } - } - - if (ReadSevMsr) { - // - // Check MSR_0xC0010131 Bit 0 (Sev Enabled) - // - Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS); - if (Msr.Bits.SevBit) { - mSevStatus = TRUE; - }- //- // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled) - // - if (Msr.Bits.SevEsBit) { - mSevEsStatus = TRUE; + // + // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled) + // + if (Msr.Bits.SevEsBit) { + mSevEsStatus = TRUE; + } } }
-=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#84133): https://edk2.groups.io/g/devel/message/84133 Mute This Topic: https://groups.io/mt/87301748/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
