From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.120]) by mx.groups.io with SMTP id smtpd.web10.4281.1590579959972603767 for ; Wed, 27 May 2020 04:46:00 -0700 Authentication-Results: mx.groups.io; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=N3HQ/slL; spf=pass (domain: redhat.com, ip: 207.211.31.120, mailfrom: lersek@redhat.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590579959; 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=y21yy/VO1sR80tu/DwXqhe5emyGbMH9LpoUwFMdnq4I=; b=N3HQ/slLOAKpTAPGuCW5w8baSq7Yc7quCPz20gEbdwG44c2YvA5W3uuQmF4VaaZVgjP+jR 0+WukxtOLbh6uvcRqVPiNgAzXdQ8TrRZtYWJ+D5utqO7NlOPTF2b8UvRVbfA+rS0K35dWB riV5hTmKPMq6uzMejZoreITXu0RmNWk= 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-469-hXIooBVSMZmdgQ6isdMtdw-1; Wed, 27 May 2020 07:45:55 -0400 X-MC-Unique: hXIooBVSMZmdgQ6isdMtdw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A67A2107ACCA; Wed, 27 May 2020 11:45:53 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-113-77.ams2.redhat.com [10.36.113.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id 61AD674EAC; Wed, 27 May 2020 11:45:50 +0000 (UTC) Subject: Re: [edk2-devel] [PATCH v8 29/46] OvmfPkg: Create a GHCB page for use during Sec phase To: Tom Lendacky , devel@edk2.groups.io Cc: Jordan Justen , Ard Biesheuvel , Michael D Kinney , Liming Gao , Eric Dong , Ray Ni , Brijesh Singh References: <85002209886afa16aa3599e4b1cb844c06f236f5.1589925074.git.thomas.lendacky@amd.com> <3f1b71c3-7e8f-61bf-16dd-b4b0cd7ff5e9@redhat.com> <1b8db197-82b6-777b-4d30-106859a89e91@amd.com> From: "Laszlo Ersek" Message-ID: <166f5022-71bf-64ce-12bf-c0ee2909be21@redhat.com> Date: Wed, 27 May 2020 13:45:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1b8db197-82b6-777b-4d30-106859a89e91@amd.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit On 05/26/20 17:41, Tom Lendacky wrote: > On 5/25/20 10:07 AM, Laszlo Ersek wrote: >> On 05/19/20 23:50, Lendacky, Thomas wrote: >>> BZ: >>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D2198&data=02%7C01%7Cthomas.lendacky%40amd.com%7C39b71c622d2d4bbf9e5b08d800bd69a5%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637260160817275268&sdata=hz43pd7UO60%2FWfNALLyUuUax8KX%2Bpq4SyU9NIN32Pfc%3D&reserved=0 >>> >>> >>> A GHCB page is needed during the Sec phase, so this new page must be >>> created. Since the #VC exception handler routines assume that a per-CPU >>> variable area is immediately after the GHCB, this per-CPU variable area >>> must also be created. Since the GHCB must be marked as an un-encrypted, >>> or shared, page, an additional pagetable page is required to break down >>> the 2MB region where the GHCB page lives into 4K pagetable entries. >>> >>> Create a new entry in the OVMF memory layout for the new page table >>> page and for the SEC GHCB and per-CPU variable pages. After breaking >>> down >>> the 2MB page, update the GHCB page table entry to remove the encryption >>> mask. >>> >>> The GHCB page will be used by the SEC #VC exception handler. The #VC >>> exception handler will fill in the necessary fields of the GHCB and exit >>> to the hypervisor using the VMGEXIT instruction. The hypervisor then >>> accesses the GHCB in order to perform the requested function. >>> >>> Two new fixed PCDs are needed to support the SEC GHCB page: >>>    - PcdOvmfSecGhcbBase  UINT64 value that is the base address of the >>>                          GHCB used during the SEC phase. >>>    - PcdOvmfSecGhcbSize  UINT64 value that is the size, in bytes, of the >>>                          GHCB area used during the SEC phase. >>> >>> Cc: Jordan Justen >>> Cc: Laszlo Ersek >>> Cc: Ard Biesheuvel >>> Reviewed-by: Laszlo Ersek >>> Signed-off-by: Tom Lendacky >>> --- >>>   OvmfPkg/OvmfPkg.dec                       |  9 +++ >>>   OvmfPkg/OvmfPkgX64.fdf                    |  6 ++ >>>   OvmfPkg/ResetVector/ResetVector.inf       |  5 ++ >>>   OvmfPkg/ResetVector/Ia32/PageTables64.asm | 70 +++++++++++++++++++++++ >>>   OvmfPkg/ResetVector/ResetVector.nasmb     | 17 ++++++ >>>   5 files changed, 107 insertions(+) >>> >>> diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec >>> index 65bb2bb0eb4c..02ad62ed9f43 100644 >>> --- a/OvmfPkg/OvmfPkg.dec >>> +++ b/OvmfPkg/OvmfPkg.dec >>> @@ -281,6 +281,15 @@ [PcdsFixedAtBuild] >>>     ## Number of page frames to use for storing grant table entries. >>>     gUefiOvmfPkgTokenSpaceGuid.PcdXenGrantFrames|4|UINT32|0x33 >>>   +  ## Specify the extra page table needed to mark the GHCB as >>> unencrypted. >>> +  #  The value should be a multiple of 4KB for each. >>> +  >>> gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase|0x0|UINT32|0x3a >>> +  >>> gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize|0x0|UINT32|0x3b >>> + >>> +  ## The base address of the SEC GHCB page used by SEV-ES. >>> +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase|0|UINT32|0x3c >>> +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize|0|UINT32|0x3d >>> + >>>   [PcdsDynamic, PcdsDynamicEx] >>>     gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2 >>>     >>> gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10 >>> >> >> OK, the token values have been updated, due to: >> >> - commit 7efce2e59c20 ("OvmfPkg/PvScsiDxe: Report the number of targets >> and LUNs", 2020-03-30) >> >> - commit c4c15b870239 ("OvmfPkg/PvScsiDxe: Support sending SCSI request >> and receive response", 2020-03-30) >> >> - commit 093cceaf79b5 ("OvmfPkg/MptScsiDxe: Report targets and one LUN", >> 2020-05-05) >> >> (Independently, when I reviewed what would become 505812ae1d2d >> ("OvmfPkg/MptScsiDxe: Implement the PassThru method", 2020-05-05), I >> missed that 0x39 is followed by 0x3A, not 0x40. Oh well.) >> >> >>> diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf >>> index bfca1eff9e83..88b1e880e603 100644 >>> --- a/OvmfPkg/OvmfPkgX64.fdf >>> +++ b/OvmfPkg/OvmfPkgX64.fdf >>> @@ -76,6 +76,12 @@ [FD.MEMFD] >>>   0x007000|0x001000 >>>   >>> gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize >>> >>>   +0x008000|0x001000 >>> +gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize >>> >>> + >>> +0x009000|0x002000 >>> +gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize >>> >>> + >>>   0x010000|0x010000 >>>   >>> gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize >>> >>>   diff --git a/OvmfPkg/ResetVector/ResetVector.inf >>> b/OvmfPkg/ResetVector/ResetVector.inf >>> index b0ddfa5832a2..483fd90fe785 100644 >>> --- a/OvmfPkg/ResetVector/ResetVector.inf >>> +++ b/OvmfPkg/ResetVector/ResetVector.inf >>> @@ -26,6 +26,7 @@ [Sources] >>>   [Packages] >>>     OvmfPkg/OvmfPkg.dec >>>     MdePkg/MdePkg.dec >>> +  MdeModulePkg/MdeModulePkg.dec >>>     UefiCpuPkg/UefiCpuPkg.dec >>>     [BuildOptions] >>> @@ -33,5 +34,9 @@ [BuildOptions] >>>      *_*_X64_NASMB_FLAGS = -I$(WORKSPACE)/UefiCpuPkg/ResetVector/Vtf0/ >>>     [Pcd] >>> +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase >>> +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize >>> +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase >>> +  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize >>>     gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase >>>     gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize >>> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm >>> b/OvmfPkg/ResetVector/Ia32/PageTables64.asm >>> index abad009f20f5..c3587a1b7814 100644 >>> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm >>> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm >>> @@ -21,6 +21,11 @@ BITS    32 >>>   %define PAGE_2M_MBO            0x080 >>>   %define PAGE_2M_PAT          0x01000 >>>   +%define PAGE_4K_PDE_ATTR (PAGE_ACCESSED + \ >>> +                          PAGE_DIRTY + \ >>> +                          PAGE_READ_WRITE + \ >>> +                          PAGE_PRESENT) >>> + >>>   %define PAGE_2M_PDE_ATTR (PAGE_2M_MBO + \ >>>                             PAGE_ACCESSED + \ >>>                             PAGE_DIRTY + \ >>> @@ -75,6 +80,37 @@ NoSev: >>>   SevExit: >>>       OneTimeCallRet CheckSevFeature >>>   +; Check if Secure Encrypted Virtualization - Encrypted State >>> (SEV-ES) feature >>> +; is enabled. >>> +; >>> +; Modified:  EAX, EBX, ECX >>> +; >>> +; If SEV-ES is enabled then EAX will be non-zero. >>> +; If SEV-ES is disabled then EAX will be zero. >>> +; >>> +CheckSevEsFeature: >>> +    xor       eax, eax >>> + >>> +    ; SEV-ES can't be enabled if SEV isn't, so first check the >>> encryption >>> +    ; mask. >>> +    test      edx, edx >>> +    jz        NoSevEs >>> + >>> +    ; Save current value of encryption mask >>> +    mov       ebx, edx >>> + >>> +    ; Check if SEV-ES is enabled >>> +    ;  MSR_0xC0010131 - Bit 1 (SEV-ES enabled) >>> +    mov       ecx, 0xc0010131 >>> +    rdmsr >>> +    and       eax, 2 >>> + >>> +    ; Restore encryption mask >>> +    mov       edx, ebx >>> + >>> +NoSevEs: >>> +    OneTimeCallRet CheckSevEsFeature >>> + >>>   ; >>>   ; Modified:  EAX, EBX, ECX, EDX >>>   ; >>> @@ -139,6 +175,40 @@ pageTableEntriesLoop: >>>       mov     [(ecx * 8 + PT_ADDR (0x2000 - 8)) + 4], edx >>>       loop    pageTableEntriesLoop >>>   +    OneTimeCall   CheckSevEsFeature >>> +    test    eax, eax >>> +    jz      SetCr3 >>> + >>> +    ; >>> +    ; The initial GHCB will live at GHCB_BASE and needs to be >>> un-encrypted. >>> +    ; This requires the 2MB page for this range be broken down into >>> 512 4KB >>> +    ; pages.  All will be marked encrypted, except for the GHCB. >>> +    ; >>> +    mov     ecx, (GHCB_BASE >> 21) >>> +    mov     eax, GHCB_PT_ADDR + PAGE_PDP_ATTR >>> +    mov     [ecx * 8 + PT_ADDR (0x2000)], eax >>> + >>> +    ; >>> +    ; Page Table Entries (512 * 4KB entries => 2MB) >>> +    ; >>> +    mov     ecx, 512 >>> +pageTableEntries4kLoop: >>> +    mov     eax, ecx >>> +    dec     eax >>> +    shl     eax, 12 >>> +    add     eax, GHCB_BASE & 0xFFE0_0000 >>> +    add     eax, PAGE_4K_PDE_ATTR >>> +    mov     [ecx * 8 + GHCB_PT_ADDR - 8], eax >>> +    mov     [(ecx * 8 + GHCB_PT_ADDR - 8) + 4], edx >>> +    loop    pageTableEntries4kLoop >>> + >>> +    ; >>> +    ; Clear the encryption bit from the GHCB entry >>> +    ; >>> +    mov     ecx, (GHCB_BASE & 0x1F_FFFF) >> 12 >>> +    mov     [ecx * 8 + GHCB_PT_ADDR + 4], strict dword 0 >>> + >> >> (1) Why did you remove "clearGhcbMemoryLoop" (in the v6->v7 transition)? > > I removed it because it actually wasn't clearing the GHCB at all. Since > this occurred before the new page tables are loaded, the page is > accessed encrypted. After loading the new page tables, the GHCB is now > referenced unencrypted and so the "zeroed" page isn't actually zeroes > anymore, it is cipher-text. > > Since the GHCB is always cleared on #VC, I dropped it. > >> >> I think that's exactly the clearing loop (minimally for the CPU#0 >> per-CPU page) that I was just looking for in point (8) under >> "OvmfPkg/VmgExitLib: Add support for DR7 Read/Write NAE events" (v8 >> 26/46). >> >> Hm... the v7 blurb says, "Ensure the per-CPU variable page remains >> encrypted". OK, but that still doesn't explain why we don't clear it >> (just for the guest to see). > > I'll add a loop to clear the GHCB page and the per-CPU page after > establishing the new page tables. > >> >> Also, if the patch was non-trivially modified in v7, then arguably my >> R-b (given originally under "RFC PATCH v3 26/43") should have been >> removed. >> >> Please re-instate "clearGhcbMemoryLoop" (and then keep the R-b). > > I'll actually drop your Reviewed-by: since I'll need to expand and move > the loop to clear the memory area from the original location in order > for the clearing of the pages to be correct. Thank you, that works for me (both code-wise and process-wise). Cheers, Laszlo