From: Tom Lendacky <[email protected]> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
The SEV support will clear the C-bit from non-RAM areas. The early GDT lives in a non-RAM area, so when an exception occurs (like a #VC) the GDT will be read as un-encrypted even though it is encrypted. This will result in a failure to be able to handle the exception. Move the GDT into RAM so it can be accessed without error when running as an SEV-ES guest. Cc: Jordan Justen <[email protected]> Cc: Laszlo Ersek <[email protected]> Cc: Ard Biesheuvel <[email protected]> Reviewed-by: Laszlo Ersek <[email protected]> Signed-off-by: Tom Lendacky <[email protected]> --- OvmfPkg/PlatformPei/AmdSev.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c index 4fd4534cabea..a2b38c591236 100644 --- a/OvmfPkg/PlatformPei/AmdSev.c +++ b/OvmfPkg/PlatformPei/AmdSev.c @@ -39,6 +39,8 @@ AmdSevEsInitialize ( PHYSICAL_ADDRESS GhcbBasePa; UINTN GhcbPageCount, PageCount; RETURN_STATUS PcdStatus, DecryptStatus; + IA32_DESCRIPTOR Gdtr; + VOID *Gdt; if (!MemEncryptSevEsIsEnabled ()) { return; @@ -83,6 +85,22 @@ AmdSevEsInitialize ( (UINT64)GhcbPageCount, GhcbBase)); AsmWriteMsr64 (MSR_SEV_ES_GHCB, GhcbBasePa); + + // + // The SEV support will clear the C-bit from non-RAM areas. The early GDT + // lives in a non-RAM area, so when an exception occurs (like a #VC) the GDT + // will be read as un-encrypted even though it was created before the C-bit + // was cleared (encrypted). This will result in a failure to be able to + // handle the exception. + // + AsmReadGdtr (&Gdtr); + + Gdt = AllocatePages (EFI_SIZE_TO_PAGES ((UINTN) Gdtr.Limit + 1)); + ASSERT (Gdt != NULL); + + CopyMem (Gdt, (VOID *) Gdtr.Base, Gdtr.Limit + 1); + Gdtr.Base = (UINTN) Gdt; + AsmWriteGdtr (&Gdtr); } /** -- 2.27.0 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#63509): https://edk2.groups.io/g/devel/message/63509 Mute This Topic: https://groups.io/mt/75892796/21656 Group Owner: [email protected] Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
