[PATCH v2 07/31] OvmfPkg/XenResetVector: Saving start of day pointer for PVH guests

["Anthony PERARD" <anthony.perard@citrix.com>]

As described in the Xen PVH documentation [1], "ebx: contains the
physical memory address where the loader has placed the boot start info
structure". To have this pointer saved to be able to use it later in the
PEI phase, we allocate some space in the MEMFD for it. We use 'XPVH' as
a signature (for "Xen PVH").

[1] https://xenbits.xenproject.org/docs/unstable/misc/pvh.html

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
 OvmfPkg/OvmfPkg.dec                         | 4 ++++
 OvmfPkg/XenOvmf.fdf                         | 4 ++++
 OvmfPkg/XenResetVector/XenResetVector.inf   | 3 +++
 OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm  | 4 ++++
 OvmfPkg/XenResetVector/XenResetVector.nasmb | 2 ++
 5 files changed, 17 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index e50c6179a2..1cbbc49a6b 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -127,6 +127,10 @@ [PcdsFixedAtBuild]
   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize|0x0|UINT32|0x1a
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd|0x0|UINT32|0x1f
 
+  # Used by XenOvmf
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenStartOfDayStructPtr|0x0|UINT32|0x30
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenStartOfDayStructPtrSize|0x0|UINT32|0x31
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/XenOvmf.fdf b/OvmfPkg/XenOvmf.fdf
index 20ebacd673..f9e58befd6 100644
--- a/OvmfPkg/XenOvmf.fdf
+++ b/OvmfPkg/XenOvmf.fdf
@@ -159,6 +159,10 @@ [FD.MEMFD]
 0x007000|0x001000
 gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
 
+0x008000|0x001000
+# Used by XenResetVector to communicate with XenPlatformPei
+gUefiOvmfPkgTokenSpaceGuid.PcdXenStartOfDayStructPtr|gUefiOvmfPkgTokenSpaceGuid.PcdXenStartOfDayStructPtrSize
+
 0x010000|0x010000
 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
diff --git a/OvmfPkg/XenResetVector/XenResetVector.inf b/OvmfPkg/XenResetVector/XenResetVector.inf
index 5c05f02285..ec98c17876 100644
--- a/OvmfPkg/XenResetVector/XenResetVector.inf
+++ b/OvmfPkg/XenResetVector/XenResetVector.inf
@@ -41,3 +41,6 @@ [BuildOptions]
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize
+
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenStartOfDayStructPtr
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenStartOfDayStructPtrSize
diff --git a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
index c4802bf4d1..4e55b0ac1f 100644
--- a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
+++ b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
@@ -22,6 +22,10 @@ xenPVHMain:
     ; ESP -  Initial value of the EAX register (BIST: Built-in Self Test)
     mov     esp, eax
 
+    ;; Store "Start of day" struct pointer for later use
+    mov     dword[PVH_SPACE (0)], ebx
+    mov     dword[PVH_SPACE (4)], 'XPVH'
+
     cli
 
     mov     ebx, ADDR_OF(gdtr)
diff --git a/OvmfPkg/XenResetVector/XenResetVector.nasmb b/OvmfPkg/XenResetVector/XenResetVector.nasmb
index d5a791c139..50cb81fcd1 100644
--- a/OvmfPkg/XenResetVector/XenResetVector.nasmb
+++ b/OvmfPkg/XenResetVector/XenResetVector.nasmb
@@ -41,6 +41,8 @@
 
 %include "CommonMacros.inc"
 
+%define PVH_SPACE(Offset) (FixedPcdGet32 (PcdXenStartOfDayStructPtr) + (Offset))
+
 %include "PostCodes.inc"
 
 %ifdef DEBUG_PORT80
-- 
Anthony PERARD