OvmfPkg/XenResetVector: Add new entry point for Xen PVH

Add a new entry point for Xen PVH that enter directly in 32bits.

Information on the expected state of the machine when this entry point
is used can be found at:
https://xenbits.xenproject.org/docs/unstable/misc/pvh.html

Also, compare to the original file [1], the two `nop' of the "resetVector"
entry point are removed. There were introduced by 8332983e2e33
("UefiCpuPkg: Replace the un-necessary WBINVD instruction at the reset
vector with two NOPs in VTF0.", 2011-08-04), but don't seems to be
useful. This is the entry point used by HVM guest (hvmloader).

[1] UefiCpuPkg/ResetVector/Vtf0/Ia16/ResetVectorVtf0.asm

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>
Message-Id: <20190813113119.14804-7-anthony.perard@citrix.com>

3 files changed, 129 insertions, 0 deletions

diff --git a/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm
new file mode 100644
index 0000000000..56749bdbc9
--- /dev/null
+++ b/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm
@@ -0,0 +1,79 @@
+;------------------------------------------------------------------------------

+; @file

+; First code executed by processor after resetting.

+;

+; Copyright (c) 2008 - 2014, Intel Corporation. All rights reserved.<BR>

+; Copyright (c) 2019, Citrix Systems, Inc.

+;

+; SPDX-License-Identifier: BSD-2-Clause-Patent

+;

+;------------------------------------------------------------------------------

+

+BITS    16

+

+ALIGN   16

+

+;

+; Pad the image size to 4k when page tables are in VTF0

+;

+; If the VTF0 image has page tables built in, then we need to make

+; sure the end of VTF0 is 4k above where the page tables end.

+;

+; This is required so the page tables will be 4k aligned when VTF0 is

+; located just below 0x100000000 (4GB) in the firmware device.

+;

+%ifdef ALIGN_TOP_TO_4K_FOR_PAGING

+    TIMES (0x1000 - ($ - EndOfPageTables) - (fourGigabytes - xenPVHEntryPoint)) DB 0

+%endif

+

+BITS    32

+xenPVHEntryPoint:

+;

+; Entry point to use when running as a Xen PVH guest. (0xffffffd0)

+;

+; Description of the expected state of the machine when this entry point is

+; used can be found at:

+; https://xenbits.xenproject.org/docs/unstable/misc/pvh.html

+;

+    jmp     xenPVHMain

+

+BITS    16

+ALIGN   16

+

+applicationProcessorEntryPoint:

+;

+; Application Processors entry point

+;

+; GenFv generates code aligned on a 4k boundary which will jump to this

+; location.  (0xffffffe0)  This allows the Local APIC Startup IPI to be

+; used to wake up the application processors.

+;

+    jmp     EarlyApInitReal16

+

+ALIGN   8

+

+    DD      0

+

+;

+; The VTF signature

+;

+; VTF-0 means that the VTF (Volume Top File) code does not require

+; any fixups.

+;

+vtfSignature:

+    DB      'V', 'T', 'F', 0

+

+ALIGN   16

+

+resetVector:

+;

+; Reset Vector

+;

+; This is where the processor will begin execution

+;

+    jmp     EarlyBspInitReal16

+

+ALIGN   16

+

+fourGigabytes:

+

diff --git a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
new file mode 100644
index 0000000000..2a17fed52f
--- /dev/null
+++ b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
@@ -0,0 +1,49 @@
+;------------------------------------------------------------------------------

+; @file

+; An entry point use by Xen when a guest is started in PVH mode.

+;

+; Copyright (c) 2019, Citrix Systems, Inc.

+;

+; SPDX-License-Identifier: BSD-2-Clause-Patent

+;

+;------------------------------------------------------------------------------

+

+BITS    32

+

+xenPVHMain:

+    ;

+    ; 'BP' to indicate boot-strap processor

+    ;

+    mov     di, 'BP'

+

+    ;

+    ; ESP will be used as initial value of the EAX register

+    ; in Main.asm

+    ;

+    xor     esp, esp

+

+    mov     ebx, ADDR_OF(gdtr)

+    lgdt    [ebx]

+

+    mov     eax, SEC_DEFAULT_CR0

+    mov     cr0, eax

+

+    jmp     LINEAR_CODE_SEL:ADDR_OF(.jmpToNewCodeSeg)

+.jmpToNewCodeSeg:

+

+    mov     eax, SEC_DEFAULT_CR4

+    mov     cr4, eax

+

+    mov     ax, LINEAR_SEL

+    mov     ds, ax

+    mov     es, ax

+    mov     fs, ax

+    mov     gs, ax

+    mov     ss, ax

+

+    ;

+    ; Jump to the main routine of the pre-SEC code

+    ; skiping the 16-bit part of the routine and

+    ; into the 32-bit flat mode part

+    ;

+    OneTimeCallRet TransitionFromReal16To32BitFlat

diff --git a/OvmfPkg/XenResetVector/XenResetVector.nasmb b/OvmfPkg/XenResetVector/XenResetVector.nasmb
index 89a4b08bc3..0dbc4f2c1d 100644
--- a/OvmfPkg/XenResetVector/XenResetVector.nasmb
+++ b/OvmfPkg/XenResetVector/XenResetVector.nasmb
@@ -63,6 +63,7 @@
 %include "Ia16/Init16.asm"

 

 %include "Main.asm"

+%include "Ia32/XenPVHMain.asm"

 

 %include "Ia16/ResetVectorVtf0.asm"