[Xen-devel] [PATCH v4 07/35] OvmfPkg/XenResetVector: Saving start of day pointer for PVH guests

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

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

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Acked-by: Laszlo Ersek <lersek@xxxxxxxxxx>
---

Notes:
    v3:
    - rename PcdXenStartOfDay* to PcdXenPvhStartOfDay*
    - Use first available token value for those (0x17 and 0x28)

 OvmfPkg/OvmfPkg.dec                         | 3 +++
 OvmfPkg/OvmfXen.fdf                         | 4 ++++
 OvmfPkg/XenResetVector/XenResetVector.inf   | 3 +++
 OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm  | 6 ++++++
 OvmfPkg/XenResetVector/XenResetVector.nasmb | 2 ++
 5 files changed, 18 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index 9640360f62..c2a2ebfb95 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -218,6 +218,9 @@ [PcdsFixedAtBuild]
   #  The value should be a multiple of 4KB.
   gUefiOvmfPkgTokenSpaceGuid.PcdHighPmmMemorySize|0x400000|UINT32|0x31
 
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtr|0x0|UINT32|0x17
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtrSize|0x0|UINT32|0x32
+
 [PcdsDynamic, PcdsDynamicEx]
   gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
diff --git a/OvmfPkg/OvmfXen.fdf b/OvmfPkg/OvmfXen.fdf
index 43c268f6cb..49997fee9b 100644
--- a/OvmfPkg/OvmfXen.fdf
+++ b/OvmfPkg/OvmfXen.fdf
@@ -172,6 +172,10 @@ [FD.MEMFD]
 0x007000|0x001000
 
gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
 
+0x008000|0x001000
+# Used by XenResetVector to communicate with XenPlatformPei
+gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtr|gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtrSize
+
 0x010000|0x010000
 
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
 
diff --git a/OvmfPkg/XenResetVector/XenResetVector.inf 
b/OvmfPkg/XenResetVector/XenResetVector.inf
index 097fc9b5b4..46b133a834 100644
--- a/OvmfPkg/XenResetVector/XenResetVector.inf
+++ b/OvmfPkg/XenResetVector/XenResetVector.inf
@@ -36,3 +36,6 @@ [BuildOptions]
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize
+
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtr
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtrSize
diff --git a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm 
b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
index 2a17fed52f..f42df3dba2 100644
--- a/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
+++ b/OvmfPkg/XenResetVector/Ia32/XenPVHMain.asm
@@ -22,6 +22,12 @@ xenPVHMain:
     ;
     xor     esp, esp
 
+    ;
+    ; Store "Start of day" struct pointer for later use
+    ;
+    mov     dword[PVH_SPACE (0)], ebx
+    mov     dword[PVH_SPACE (4)], 'XPVH'
+
     mov     ebx, ADDR_OF(gdtr)
     lgdt    [ebx]
 
diff --git a/OvmfPkg/XenResetVector/XenResetVector.nasmb 
b/OvmfPkg/XenResetVector/XenResetVector.nasmb
index 0dbc4f2c1d..b2cb405d54 100644
--- a/OvmfPkg/XenResetVector/XenResetVector.nasmb
+++ b/OvmfPkg/XenResetVector/XenResetVector.nasmb
@@ -34,6 +34,8 @@
 
 %include "CommonMacros.inc"
 
+%define PVH_SPACE(Offset) (FixedPcdGet32 (PcdXenPvhStartOfDayStructPtr) + 
(Offset))
+
 %include "PostCodes.inc"
 
 %ifdef DEBUG_PORT80
-- 
Anthony PERARD

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