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From: Laszlo Ersek <lersek@redhat.com>
To: anthony.perard@citrix.com
Cc: Jordan Justen <jordan.l.justen@intel.com>,
	devel@edk2.groups.io, Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Julien Grall <julien.grall@arm.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [edk2-devel] [PATCH v5 08/35] OvmfPkg/XenResetVector: Allow jumpstart from either hvmloader or PVH
Date: Wed, 21 Aug 2019 18:31:04 +0200
Message-ID: <92bbc5f1-6b08-a2e9-8731-e0e5a3ca132a@redhat.com> (raw)
In-Reply-To: <20190813113119.14804-9-anthony.perard@citrix.com>

Hi Anthony,

On 08/13/19 13:30, Anthony PERARD wrote:
> This patch allows the ResetVector to be run indenpendently from build
> time addresses.
> 
> The goal of the patch is to avoid having to create RAM just below 4G
> when creating a Xen PVH guest while being compatible with the way
> hvmloader currently load OVMF, just below 4G.
> 
> Only the new PVH entry point will do the calculation.
> 
> The ResetVector will figure out its current running address by creating
> a temporary stack, make a call and calculate the difference between the
> build time address and the address at run time.
> 
> This patch copies and make the necessary modification to some other asm
> files:
> - copy of UefiCpuPkg/.../Flat32ToFlat64.asm:
>   Allow Transition32FlatTo64Flat to be run from anywhere in memory
> - copy of UefiCpuPkg/../SearchForBfvBase.asm:
>   Add a extra parameter to indicate where to start the search for the
>   boot firmware volume.
> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> Acked-by: Laszlo Ersek <lersek@redhat.com>
> ---
> 
> Notes:
>     v3:
>     - rebased, SPDX
>     - fix commit message
> 
>  .../XenResetVector/Ia16/Real16ToFlat32.asm    |  3 +
>  .../XenResetVector/Ia32/Flat32ToFlat64.asm    | 68 +++++++++++++++
>  .../XenResetVector/Ia32/SearchForBfvBase.asm  | 87 +++++++++++++++++++
>  OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm    | 43 +++++++--
>  4 files changed, 194 insertions(+), 7 deletions(-)
>  create mode 100644 OvmfPkg/XenResetVector/Ia32/Flat32ToFlat64.asm
>  create mode 100644 OvmfPkg/XenResetVector/Ia32/SearchForBfvBase.asm
> 
> diff --git a/OvmfPkg/XenResetVector/Ia16/Real16ToFlat32.asm b/OvmfPkg/XenResetVector/Ia16/Real16ToFlat32.asm
> index 5c329bfaea..36ea74f7fe 100644
> --- a/OvmfPkg/XenResetVector/Ia16/Real16ToFlat32.asm
> +++ b/OvmfPkg/XenResetVector/Ia16/Real16ToFlat32.asm
> @@ -54,6 +54,9 @@ jumpTo32BitAndLandHere:
>      mov     gs, ax
>      mov     ss, ax
>  
> +    ; parameter for Flat32SearchForBfvBase
> +    xor     eax, eax ; Start searching from top of 4GB for BfvBase
> +
>      OneTimeCallRet TransitionFromReal16To32BitFlat
>  
>  ALIGN   2
> diff --git a/OvmfPkg/XenResetVector/Ia32/Flat32ToFlat64.asm b/OvmfPkg/XenResetVector/Ia32/Flat32ToFlat64.asm
> new file mode 100644
> index 0000000000..661a8e7028
> --- /dev/null
> +++ b/OvmfPkg/XenResetVector/Ia32/Flat32ToFlat64.asm
> @@ -0,0 +1,68 @@
> +;------------------------------------------------------------------------------
> +; @file
> +; Transition from 32 bit flat protected mode into 64 bit flat protected mode
> +;
> +; Copyright (c) 2008 - 2018, Intel Corporation. All rights reserved.<BR>
> +; Copyright (c) 2019, Citrix Systems, Inc.
> +;
> +; SPDX-License-Identifier: BSD-2-Clause-Patent
> +;
> +;------------------------------------------------------------------------------
> +
> +BITS    32
> +
> +;
> +; Modified:  EAX, EBX, ECX, EDX, ESP
> +;
> +Transition32FlatTo64Flat:
> +
> +    OneTimeCall SetCr3ForPageTables64
> +
> +    mov     eax, cr4
> +    bts     eax, 5                      ; enable PAE
> +    mov     cr4, eax
> +
> +    mov     ecx, 0xc0000080
> +    rdmsr
> +    bts     eax, 8                      ; set LME
> +    wrmsr
> +
> +    mov     eax, cr0
> +    bts     eax, 31                     ; set PG
> +    mov     cr0, eax                    ; enable paging
> +
> +    ;
> +    ; backup ESP
> +    ;
> +    mov     ebx, esp
> +
> +    ;
> +    ; recalculate delta
> +    ;
> +    mov     esp, PVH_SPACE(16)
> +    call    .delta
> +.delta:
> +    pop     edx
> +    sub     edx, ADDR_OF(.delta)
> +
> +    ;
> +    ; push return addr and seg to the stack, then return far
> +    ;
> +    push    dword LINEAR_CODE64_SEL
> +    mov     eax, ADDR_OF(jumpTo64BitAndLandHere)
> +    add     eax, edx                             ; add delta
> +    push    eax
> +    retf
> +
> +BITS    64
> +jumpTo64BitAndLandHere:
> +
> +    ;
> +    ; restore ESP
> +    ;
> +    mov     esp, ebx
> +
> +    debugShowPostCode POSTCODE_64BIT_MODE
> +
> +    OneTimeCallRet Transition32FlatTo64Flat
> +
> diff --git a/OvmfPkg/XenResetVector/Ia32/SearchForBfvBase.asm b/OvmfPkg/XenResetVector/Ia32/SearchForBfvBase.asm
> new file mode 100644
> index 0000000000..190389c46f
> --- /dev/null
> +++ b/OvmfPkg/XenResetVector/Ia32/SearchForBfvBase.asm
> @@ -0,0 +1,87 @@
> +;------------------------------------------------------------------------------
> +; @file
> +; Search for the Boot Firmware Volume (BFV) base address
> +;
> +; Copyright (c) 2008 - 2009, Intel Corporation. All rights reserved.<BR>
> +; Copyright (c) 2019, Citrix Systems, Inc.
> +;
> +; SPDX-License-Identifier: BSD-2-Clause-Patent
> +;
> +;------------------------------------------------------------------------------
> +
> +;#define EFI_FIRMWARE_FILE_SYSTEM2_GUID \
> +;  { 0x8c8ce578, 0x8a3d, 0x4f1c, { 0x99, 0x35, 0x89, 0x61, 0x85, 0xc3, 0x2d, 0xd3 } }
> +%define FFS_GUID_DWORD0 0x8c8ce578
> +%define FFS_GUID_DWORD1 0x4f1c8a3d
> +%define FFS_GUID_DWORD2 0x61893599
> +%define FFS_GUID_DWORD3 0xd32dc385
> +
> +BITS    32
> +
> +;
> +; Modified:  EAX, EBX, ECX
> +; Preserved: EDI, ESP
> +;
> +; @param[in]   EAX  Start search from here
> +; @param[out]  EBP  Address of Boot Firmware Volume (BFV)
> +;
> +Flat32SearchForBfvBase:
> +
> +    mov     ecx, eax
> +searchingForBfvHeaderLoop:
> +    ;
> +    ; We check for a firmware volume at every 4KB address in the 16MB
> +    ; just below where we started, ECX.
> +    ;
> +    sub     eax, 0x1000
> +    mov     ebx, ecx
> +    sub     ebx, eax
> +    cmp     ebx, 0x01000000
> +    ; if ECX-EAX > 16MB; jump notfound
> +    ja      searchedForBfvHeaderButNotFound
> +
> +    ;
> +    ; Check FFS GUID
> +    ;
> +    cmp     dword [eax + 0x10], FFS_GUID_DWORD0
> +    jne     searchingForBfvHeaderLoop
> +    cmp     dword [eax + 0x14], FFS_GUID_DWORD1
> +    jne     searchingForBfvHeaderLoop
> +    cmp     dword [eax + 0x18], FFS_GUID_DWORD2
> +    jne     searchingForBfvHeaderLoop
> +    cmp     dword [eax + 0x1c], FFS_GUID_DWORD3
> +    jne     searchingForBfvHeaderLoop
> +
> +    ;
> +    ; Check FV Length
> +    ;
> +    cmp     dword [eax + 0x24], 0
> +    jne     searchingForBfvHeaderLoop
> +    mov     ebx, eax
> +    add     ebx, dword [eax + 0x20]
> +    cmp     ebx, ecx
> +    jnz     searchingForBfvHeaderLoop
> +
> +    jmp     searchedForBfvHeaderAndItWasFound
> +
> +searchedForBfvHeaderButNotFound:
> +    ;
> +    ; Hang if the SEC entry point was not found
> +    ;
> +    debugShowPostCode POSTCODE_BFV_NOT_FOUND
> +
> +    ;
> +    ; 0xbfbfbfbf in the EAX & EBP registers helps signal what failed
> +    ; for debugging purposes.
> +    ;
> +    mov     eax, 0xBFBFBFBF
> +    mov     ebp, eax
> +    jmp     $
> +
> +searchedForBfvHeaderAndItWasFound:
> +    mov     ebp, eax
> +
> +    debugShowPostCode POSTCODE_BFV_FOUND
> +
> +    OneTimeCallRet Flat32SearchForBfvBase
> +
> diff --git a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
> index f42df3dba2..2df0f12e18 100644
> --- a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
> +++ b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
> @@ -16,25 +16,42 @@ xenPVHMain:
>      ;
>      mov     di, 'BP'
>  
> -    ;
> -    ; ESP will be used as initial value of the EAX register
> -    ; in Main.asm
> -    ;
> -    xor     esp, esp
> -
>      ;
>      ; Store "Start of day" struct pointer for later use
>      ;
>      mov     dword[PVH_SPACE (0)], ebx
>      mov     dword[PVH_SPACE (4)], 'XPVH'
>  
> +    ;
> +    ; calculate delta between build-addr and run position
> +    ;
> +    mov     esp, PVH_SPACE(16)          ; create a temporary stack
> +    call    .delta
> +.delta:
> +    pop     edx                         ; get addr of .delta
> +    sub     edx, ADDR_OF(.delta)        ; calculate delta
> +
> +    ;
> +    ; Find address of GDT and gdtr and fix the later
> +    ;
>      mov     ebx, ADDR_OF(gdtr)
> +    add     ebx, edx                    ; add delta gdtr
> +    mov     eax, ADDR_OF(GDT_BASE)
> +    add     eax, edx                    ; add delta to GDT_BASE
> +    mov     dword[ebx + 2], eax         ; fix GDT_BASE addr in gdtr
>      lgdt    [ebx]
>  
>      mov     eax, SEC_DEFAULT_CR0
>      mov     cr0, eax
>  
> -    jmp     LINEAR_CODE_SEL:ADDR_OF(.jmpToNewCodeSeg)
> +    ;
> +    ; push return addr to the stack, then return far
> +    ;
> +    push    dword LINEAR_CODE_SEL          ; segment to select
> +    mov     eax, ADDR_OF(.jmpToNewCodeSeg) ; return addr
> +    add     eax, edx                       ; add delta to return addr
> +    push    eax
> +    retf
>  .jmpToNewCodeSeg:
>  
>      mov     eax, SEC_DEFAULT_CR4
> @@ -47,6 +64,18 @@ xenPVHMain:
>      mov     gs, ax
>      mov     ss, ax
>  
> +    ;
> +    ; ESP will be used as initial value of the EAX register
> +    ; in Main.asm
> +    ;
> +    xor     esp, esp
> +
> +    ;
> +    ; parameter for Flat32SearchForBfvBase
> +    ;
> +    mov     eax, ADDR_OF(fourGigabytes)

I've just noticed that the line above triggers the following NASM warning:

Ia32/XenPVHMain.asm:76: warning: dword data exceeds bounds

The warning does not stop the build.

The macro comes from "UefiCpuPkg/ResetVector/Vtf0/CommonMacros.inc":

%define ADDR_OF(x) (0x100000000 - fourGigabytes + x)

So I believe we effectively store 0 to EAX. If that's the intent (I
think it *could* be), please submit a cleanup in the next development
cycle -- we could store a 0 explicitly and add a comment, just to shut
up the warning. If, on the other hand, this is a bug, please submit a
fix soon (for the upcoming release).

Thanks
Laszlo


> +    add     eax, edx ; add delta
> +
>      ;
>      ; Jump to the main routine of the pre-SEC code
>      ; skiping the 16-bit part of the routine and
> 


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  reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-13 11:30 [Xen-devel] [PATCH v5 00/35] Specific platform to run OVMF in Xen PVH and HVM guests Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 01/35] OvmfPkg/ResetSystemLib: Add missing dependency on PciLib Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 02/35] OvmfPkg: Create platform OvmfXen Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 03/35] OvmfPkg: Introduce XenResetVector Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 04/35] OvmfPkg: Introduce XenPlatformPei Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 05/35] OvmfPkg/OvmfXen: Creating an ELF header Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 06/35] OvmfPkg/XenResetVector: Add new entry point for Xen PVH Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 07/35] OvmfPkg/XenResetVector: Saving start of day pointer for PVH guests Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 08/35] OvmfPkg/XenResetVector: Allow jumpstart from either hvmloader or PVH Anthony PERARD
2019-08-21 16:31   ` Laszlo Ersek [this message]
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 10/35] OvmfPkg/XenPlatformPei: Detect OVMF_INFO from hvmloader Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 11/35] OvmfPkg/XenPlatformPei: Use mXenHvmloaderInfo to get E820 Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 12/35] OvmfPkg/XenPlatformPei: Grab RSDP from PVH guest start of day struct Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 13/35] OvmfPkg/Library/XenPlatformLib: New library Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 14/35] OvmfPkg/AcpiPlatformDxe: Use XenPlatformLib Anthony PERARD
2019-08-13 11:30 ` [Xen-devel] [PATCH v5 15/35] OvmfPkg/AcpiPlatformDxe: Use Xen PVH RSDP if it exist Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 16/35] OvmfPkg/XenHypercallLib: Enable it in PEIM Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 17/35] OvmfPkg/XenPlatformPei: Reinit XenHypercallLib Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 18/35] OvmfPkg/XenPlatformPei: Introduce XenHvmloaderDetected Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 19/35] OvmfPkg/XenPlatformPei: Setup HyperPages earlier Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 20/35] OvmfPkg/XenPlatformPei: Introduce XenPvhDetected Anthony PERARD
2019-08-15  8:54   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 21/35] OvmfPkg: Import XENMEM_memory_map hypercall to Xen/memory.h Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 22/35] OvmfPkg/XenPlatformPei: no hvmloader: get the E820 table via hypercall Anthony PERARD
2019-08-15  8:59   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 23/35] OvmfPkg/XenPlatformPei: Rework memory detection Anthony PERARD
2019-08-15  9:26   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 24/35] OvmfPkg/XenPlatformPei: Reserve VGA memory region, to boot Linux Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 25/35] OvmfPkg/XenPlatformPei: Ignore missing PCI Host Bridge on Xen PVH Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 26/35] OvmfPkg/XenPlatformLib: Cache result for XenDetected Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 27/35] OvmfPkg/PlatformBootManagerLib: Use XenDetected from XenPlatformLib Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 28/35] OvmfPkg/PlatformBootManagerLib: Handle the absence of PCI bus on Xen PVH Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 29/35] OvmfPkg/OvmfXen: Override PcdFSBClock to Xen vLAPIC timer frequency Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 30/35] OvmfPkg/OvmfXen: Introduce XenTimerDxe Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 31/35] OvmfPkg/PlatformBootManagerLib: Use a Xen console for ConOut/ConIn Anthony PERARD
2019-08-15  9:35   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 32/35] OvmfPkg: Introduce PcdXenGrantFrames Anthony PERARD
2019-08-15  9:40   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-15  9:45     ` Laszlo Ersek
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 33/35] OvmfPkg: Introduce XenIoPvhDxe to initialize Grant Tables Anthony PERARD
2019-08-15  9:42   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 34/35] OvmfPkg: Move XenRealTimeClockLib from ArmVirtPkg Anthony PERARD
2019-08-13 11:31 ` [Xen-devel] [PATCH v5 35/35] OvmfPkg/OvmfXen: use RealTimeClockRuntimeDxe from EmbeddedPkg Anthony PERARD
2019-08-15 11:03 ` [Xen-devel] [edk2-devel] [PATCH v5 00/35] Specific platform to run OVMF in Xen PVH and HVM guests Laszlo Ersek
2019-08-21 16:16   ` Laszlo Ersek

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