diff options
| -rw-r--r-- | OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm | 51 |
1 files changed, 40 insertions, 11 deletions
diff --git a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm index 980e0138e7..9e0a74fddf 100644 --- a/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm +++ b/OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm @@ -26,20 +26,39 @@ ALIGN 16 %endif
;
+; Padding to ensure first guid starts at 0xffffffd0
+;
+TIMES (15 - ((guidedStructureEnd - guidedStructureStart + 15) % 16)) DB 0
+
+; GUIDed structure. To traverse this you should first verify the
+; presence of the table footer guid
+; (96b582de-1fb2-45f7-baea-a366c55a082d) at 0xffffffd0. If that
+; is found, the two bytes at 0xffffffce are the entire table length.
+;
+; The table is composed of structures with the form:
+;
+; Data (arbitrary bytes identified by guid)
+; length from start of data to end of guid (2 bytes)
+; guid (16 bytes)
+;
+; so work back from the footer using the length to traverse until you
+; either find the guid you're looking for or run off the beginning of
+; the table.
+;
+guidedStructureStart:
+
+;
; SEV-ES Processor Reset support
;
; sevEsResetBlock:
; For the initial boot of an AP under SEV-ES, the "reset" RIP must be
-; programmed to the RAM area defined by SEV_ES_AP_RESET_IP. A known offset
-; and GUID will be used to locate this block in the firmware and extract
-; the build time RIP value. The GUID must always be 48 bytes from the
-; end of the firmware.
+; programmed to the RAM area defined by SEV_ES_AP_RESET_IP. The data
+; format is:
;
-; 0xffffffca (-0x36) - IP value
-; 0xffffffcc (-0x34) - CS segment base [31:16]
-; 0xffffffce (-0x32) - Size of the SEV-ES reset block
-; 0xffffffd0 (-0x30) - SEV-ES reset block GUID
-; (00f771de-1a7e-4fcb-890e-68c77e2fb44e)
+; IP value [0:15]
+; CS segment base [31:16]
+;
+; GUID (SEV-ES reset block): 00f771de-1a7e-4fcb-890e-68c77e2fb44e
;
; A hypervisor reads the CS segement base and IP value. The CS segment base
; value represents the high order 16-bits of the CS segment base, so the
@@ -48,8 +67,6 @@ ALIGN 16 ; program the EIP register with the IP value as read.
;
-TIMES (32 - (sevEsResetBlockEnd - sevEsResetBlockStart)) DB 0
-
sevEsResetBlockStart:
DD SEV_ES_AP_RESET_IP
DW sevEsResetBlockEnd - sevEsResetBlockStart
@@ -57,6 +74,18 @@ sevEsResetBlockStart: DB 0x89, 0x0E, 0x68, 0xC7, 0x7E, 0x2F, 0xB4, 0x4E
sevEsResetBlockEnd:
+;
+; Table footer:
+;
+; length of whole table (16 bit word)
+; GUID (table footer): 96b582de-1fb2-45f7-baea-a366c55a082d
+;
+ DW guidedStructureEnd - guidedStructureStart
+ DB 0xDE, 0x82, 0xB5, 0x96, 0xB2, 0x1F, 0xF7, 0x45
+ DB 0xBA, 0xEA, 0xA3, 0x66, 0xC5, 0x5A, 0x08, 0x2D
+
+guidedStructureEnd:
+
ALIGN 16
applicationProcessorEntryPoint:
|