From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by mx.groups.io with SMTP id smtpd.web10.7138.1619168867549212847 for ; Fri, 23 Apr 2021 02:07:47 -0700 Authentication-Results: mx.groups.io; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=ZRwKXmXh; spf=pass (domain: redhat.com, ip: 170.10.133.124, mailfrom: lersek@redhat.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619168866; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=R467LmbpsCiORvleyprjVwme2VlPdPMi0goNiOqEDUQ=; b=ZRwKXmXh8hDeUSk9F06z5pTWGQVd+8q0Jp8eZY8za1oUPM0O/2A8eEFakgforIcqBVe6bG lEs35taI8yn9qhEvsM+E33Gc1xODiXWIT6Rywwd/yRPsR0BhjfSiLXSMO7ODDnfaL0RMYZ xoIAUcWPaHrh4J+LXuQc+Y14NHuPnUM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-274-lMh-WRiBPN6jlrKK9NQ27w-1; Fri, 23 Apr 2021 05:07:42 -0400 X-MC-Unique: lMh-WRiBPN6jlrKK9NQ27w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0576A343A2; Fri, 23 Apr 2021 09:07:41 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-115-2.ams2.redhat.com [10.36.115.2]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8695560C21; Fri, 23 Apr 2021 09:07:37 +0000 (UTC) Subject: Re: [edk2-devel] [PATCH 1/3] OvfmPkg/VmgExitLib: Properly decode MMIO MOVZX and MOVSX opcodes To: Tom Lendacky , devel@edk2.groups.io Cc: Joerg Roedel , Borislav Petkov , Ard Biesheuvel , Jordan Justen , Brijesh Singh , James Bottomley , Jiewen Yao , Min Xu References: <71864a75c680c4f7f07ebf9611c9cc2d351ce5d0.1618959281.git.thomas.lendacky@amd.com> <7bf6b4ce-85c7-578e-973a-f976bdfa706b@redhat.com> <56f2c943-523e-46d5-dc4d-19e2bb31b07b@amd.com> From: "Laszlo Ersek" Message-ID: <040a4754-74cb-0281-5312-a449016e2a27@redhat.com> Date: Fri, 23 Apr 2021 11:07:36 +0200 MIME-Version: 1.0 In-Reply-To: <56f2c943-523e-46d5-dc4d-19e2bb31b07b@amd.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=lersek@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 04/22/21 15:35, Tom Lendacky wrote: > On 4/22/21 12:28 AM, Laszlo Ersek wrote: >> On 04/21/21 00:54, Lendacky, Thomas wrote: >>> From: Tom Lendacky >>> >>> BZ: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D3345&data=04%7C01%7Cthomas.lendacky%40amd.com%7C22bf3a3ae9cb4421e93208d9054f79c8%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637546661229697941%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=1EmUDf%2FfuCuu%2BkXPZijzatfliplMhKEQH8kiZ9Z8ZF0%3D&reserved=0 >>> >>> The MOVZX and MOVSX instructions use the ModRM byte in the instruction, >>> but the instruction decoding support was not decoding it. This resulted >>> in invalid decoding and failing of the MMIO operation. Also, when >>> performing the zero-extend or sign-extend operation, the memory operation >>> should be using the size, and not the size enumeration value. >>> >>> Add the ModRM byte decoding for the MOVZX and MOVSX opcodes and use the >>> true data size to perform the extend operations. Additionally, add a >>> DEBUG statement identifying the MMIO address being flagged as encrypted >>> during the MMIO address validation. >>> >>> Fixes: c45f678a1ea2080344e125dc55b14e4b9f98483d >>> Cc: Laszlo Ersek >>> Cc: Ard Biesheuvel >>> Cc: Jordan Justen >>> Cc: Brijesh Singh >>> Cc: James Bottomley >>> Cc: Jiewen Yao >>> Cc: Min Xu >>> Signed-off-by: Tom Lendacky >>> --- >>> OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c | 7 +++++-- >>> 1 file changed, 5 insertions(+), 2 deletions(-) >>> >>> diff --git a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c >>> index 24259060fd65..273f36499988 100644 >>> --- a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c >>> +++ b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c >>> @@ -643,6 +643,7 @@ ValidateMmioMemory ( >>> // >>> // Any state other than unencrypted is an error, issue a #GP. >>> // >>> + DEBUG ((DEBUG_INFO, "MMIO using encrypted memory: %lx\n", MemoryAddress)); >>> GpEvent.Uint64 = 0; >>> GpEvent.Elements.Vector = GP_EXCEPTION; >>> GpEvent.Elements.Type = GHCB_EVENT_INJECTION_TYPE_EXCEPTION; >> >> (1) This can potentially generate a large number of debug messages; >> please use the DEBUG_VERBOSE log mask. > > Actually, you will see this only once since the code will propagate a GP > and the guest will terminate in this situation. Ugh, sorry, I must have completely lost track of the context here. I apologize. In that case however, it should be DEBUG_ERROR. Thanks, Laszlo > >> >> (2) "MemoryAddress" has type UINTN, but %lx takes UINT64. Given that >> this is X64-only code, functionally there is no bug, but it's still >> cleaner to pass "(UINT64)MemoryAddress" to %lx. > > Will do. > > Thanks, > Tom > >> >> With that: >> >> Acked-by: Laszlo Ersek >> >> Thanks >> Laszlo >> >> >>> @@ -817,6 +818,7 @@ MmioExit ( >>> // fall through >>> // >>> case 0xB7: >>> + DecodeModRm (Regs, InstructionData); >>> Bytes = (Bytes != 0) ? Bytes : 2; >>> >>> Status = ValidateMmioMemory (Ghcb, InstructionData->Ext.RmData, Bytes); >>> @@ -835,7 +837,7 @@ MmioExit ( >>> } >>> >>> Register = GetRegisterPointer (Regs, InstructionData->Ext.ModRm.Reg); >>> - SetMem (Register, InstructionData->DataSize, 0); >>> + SetMem (Register, (UINTN) (1 << InstructionData->DataSize), 0); >>> CopyMem (Register, Ghcb->SharedBuffer, Bytes); >>> break; >>> >>> @@ -848,6 +850,7 @@ MmioExit ( >>> // fall through >>> // >>> case 0xBF: >>> + DecodeModRm (Regs, InstructionData); >>> Bytes = (Bytes != 0) ? Bytes : 2; >>> >>> Status = ValidateMmioMemory (Ghcb, InstructionData->Ext.RmData, Bytes); >>> @@ -878,7 +881,7 @@ MmioExit ( >>> } >>> >>> Register = GetRegisterPointer (Regs, InstructionData->Ext.ModRm.Reg); >>> - SetMem (Register, InstructionData->DataSize, SignByte); >>> + SetMem (Register, (UINTN) (1 << InstructionData->DataSize), SignByte); >>> CopyMem (Register, Ghcb->SharedBuffer, Bytes); >>> break; >>> >>> >> >