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contact devel+owner@edk2.groups.io Reply-To: devel@edk2.groups.io,thomas.lendacky@amd.com X-Gm-Message-State: NfXcdtIfnejmlUcRRjnxhsvRx1787277AA= Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=groups.io; q=dns/txt; s=20140610; t=1595366649; bh=YaeAtDCZU45lRsxpEdbBIWEKn3a82q0zI/0HeELdjjo=; h=CC:Content-Type:Date:From:Reply-To:Subject:To; b=jPga8Tl1aipAfU1nBrU/CikHGiK3pKfwirKNAuBxsX1e08Rw2DfwW2b8Y5ISH7MliNL AEkrRhYj6UEXi03Y1/HlVRcS6mqpLZBHphp6gXqG5X44bBgMt1wiYgfbBul2oJa9XlXPr JYVfUBN/kpb7KQ0wKAr2GsQxwEVUS9JkAi8= X-ZohoMail-DKIM: pass (identity @groups.io) Content-Type: text/plain; charset="utf-8" From: Tom Lendacky BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3D2198 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 Cc: Laszlo Ersek Cc: Ard Biesheuvel Reviewed-by: Laszlo Ersek Signed-off-by: Tom Lendacky --- 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; =20 if (!MemEncryptSevEsIsEnabled ()) { return; @@ -83,6 +85,22 @@ AmdSevEsInitialize ( (UINT64)GhcbPageCount, GhcbBase)); =20 AsmWriteMsr64 (MSR_SEV_ES_GHCB, GhcbBasePa); + + // + // The SEV support will clear the C-bit from non-RAM areas. The early G= DT + // 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 =3D AllocatePages (EFI_SIZE_TO_PAGES ((UINTN) Gdtr.Limit + 1)); + ASSERT (Gdt !=3D NULL); + + CopyMem (Gdt, (VOID *) Gdtr.Base, Gdtr.Limit + 1); + Gdtr.Base =3D (UINTN) Gdt; + AsmWriteGdtr (&Gdtr); } =20 /** --=20 2.27.0 -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#63023): https://edk2.groups.io/g/devel/message/63023 Mute This Topic: https://groups.io/mt/75713151/1787277 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [importer@patchew.org] -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-