[edk2-devel] [PATCH v2 3/3] OvmfPkg/ResetVector: move the GHCB page setup in AmdSev.asm
Brijesh Singh via groups.io
brijesh.singh=amd.com at groups.io
Thu Aug 5 20:42:14 UTC 2021
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3429
While build the initial page table, the SetCr3ForPageTables64 checks
whether SEV-ES is enabled. If so, clear the page encryption mask from the
GHCB page. Move the logic to clear the page encryption mask in the
AmdSev.asm.
Cc: James Bottomley <jejb at linux.ibm.com>
Cc: Min Xu <min.m.xu at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Erdem Aktas <erdemaktas at google.com>
Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
---
OvmfPkg/ResetVector/Ia32/AmdSev.asm | 113 +++++++++++++++++-----
OvmfPkg/ResetVector/Ia32/PageTables64.asm | 53 ++--------
2 files changed, 94 insertions(+), 72 deletions(-)
diff --git a/OvmfPkg/ResetVector/Ia32/AmdSev.asm b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
index 87d81b01e263..fd2e6abcd4a0 100644
--- a/OvmfPkg/ResetVector/Ia32/AmdSev.asm
+++ b/OvmfPkg/ResetVector/Ia32/AmdSev.asm
@@ -44,6 +44,27 @@ BITS 32
; The unexpected response code
%define TERM_UNEXPECTED_RESP_CODE 2
+%define PAGE_PRESENT 0x01
+%define PAGE_READ_WRITE 0x02
+%define PAGE_USER_SUPERVISOR 0x04
+%define PAGE_WRITE_THROUGH 0x08
+%define PAGE_CACHE_DISABLE 0x010
+%define PAGE_ACCESSED 0x020
+%define PAGE_DIRTY 0x040
+%define PAGE_PAT 0x080
+%define PAGE_GLOBAL 0x0100
+%define PAGE_2M_MBO 0x080
+%define PAGE_2M_PAT 0x01000
+
+%define PAGE_4K_PDE_ATTR (PAGE_ACCESSED + \
+ PAGE_DIRTY + \
+ PAGE_READ_WRITE + \
+ PAGE_PRESENT)
+
+%define PAGE_PDP_ATTR (PAGE_ACCESSED + \
+ PAGE_READ_WRITE + \
+ PAGE_PRESENT)
+
; Macro is used to issue the MSR protocol based VMGEXIT. The caller is
; responsible to populate values in the EDX:EAX registers. After the vmmcall
@@ -117,6 +138,72 @@ BITS 32
SevEsUnexpectedRespTerminate:
TerminateVmgExit TERM_UNEXPECTED_RESP_CODE
+; If SEV-ES is enabled then initialize the make the GHCB page shared
+SevClearPageEncMaskFromGHCBPage:
+ ; Check if SEV is enabled
+ cmp byte[WORK_AREA_GUEST_TYPE], 1
+ jnz SevClearPageEncMaskFromGHCBPageExit
+
+ ; Check if SEV-ES is enabled
+ cmp byte[SEV_ES_WORK_AREA], 1
+ jnz SevClearPageEncMaskFromGHCBPageExit
+
+ ;
+ ; The initial GHCB will live at GHCB_BASE and needs to be un-encrypted.
+ ; This requires the 2MB page for this range be broken down into 512 4KB
+ ; pages. All will be marked encrypted, except for the GHCB.
+ ;
+ mov ecx, (GHCB_BASE >> 21)
+ mov eax, GHCB_PT_ADDR + PAGE_PDP_ATTR
+ mov [ecx * 8 + PT_ADDR (0x2000)], eax
+
+ ;
+ ; Page Table Entries (512 * 4KB entries => 2MB)
+ ;
+ mov ecx, 512
+pageTableEntries4kLoop:
+ mov eax, ecx
+ dec eax
+ shl eax, 12
+ add eax, GHCB_BASE & 0xFFE0_0000
+ add eax, PAGE_4K_PDE_ATTR
+ mov [ecx * 8 + GHCB_PT_ADDR - 8], eax
+ mov [(ecx * 8 + GHCB_PT_ADDR - 8) + 4], edx
+ loop pageTableEntries4kLoop
+
+ ;
+ ; Clear the encryption bit from the GHCB entry
+ ;
+ mov ecx, (GHCB_BASE & 0x1F_FFFF) >> 12
+ mov [ecx * 8 + GHCB_PT_ADDR + 4], strict dword 0
+
+ mov ecx, GHCB_SIZE / 4
+ xor eax, eax
+clearGhcbMemoryLoop:
+ mov dword[ecx * 4 + GHCB_BASE - 4], eax
+ loop clearGhcbMemoryLoop
+
+SevClearPageEncMaskFromGHCBPageExit:
+ OneTimeCallRet SevClearPageEncMaskFromGHCBPage
+
+; Check if SEV is enabled, and get the C-bit mask above 31.
+; Modified: EDX
+;
+; The value is returned in the EDX
+GetSevCBitMaskAbove31:
+ ; Check if SEV is enabled
+ cmp byte[WORK_AREA_GUEST_TYPE], 1
+ jnz NoCbitValue
+
+ mov edx, dword[SEV_ES_WORK_AREA_ENC_MASK + 4]
+ jmp GetSevCBitMaskAbove31Exit
+
+NoCbitValue:
+ xor edx, edx
+
+GetSevCBitMaskAbove31Exit:
+ OneTimeCallRet GetSevCBitMaskAbove31
+
; Check if Secure Encrypted Virtualization (SEV) features are enabled.
;
; Register usage is tight in this routine, so multiple calls for the
@@ -249,32 +336,6 @@ SevExit:
OneTimeCallRet CheckSevFeatures
-; Check if Secure Encrypted Virtualization - Encrypted State (SEV-ES) feature
-; is enabled.
-;
-; Modified: EAX
-;
-; If SEV-ES is enabled then EAX will be non-zero.
-; If SEV-ES is disabled then EAX will be zero.
-;
-IsSevEsEnabled:
- xor eax, eax
-
- ; During CheckSevFeatures, the WORK_AREA_GUEST_TYPE is set
- ; to 1 if SEV is enabled.
- cmp byte[WORK_AREA_GUEST_TYPE], 1
- jne SevEsDisabled
-
- ; During CheckSevFeatures, the SEV_ES_WORK_AREA was set to 1 if
- ; SEV-ES is enabled.
- cmp byte[SEV_ES_WORK_AREA], 1
- jne SevEsDisabled
-
- mov eax, 1
-
-SevEsDisabled:
- OneTimeCallRet IsSevEsEnabled
-
; Start of #VC exception handling routines
;
diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
index f688909f1c7d..0e8ba4dde534 100644
--- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
+++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
@@ -46,16 +46,13 @@ SetCr3ForPageTables64:
; work area when detected.
mov byte[WORK_AREA_GUEST_TYPE], 0
+ ; Check whether the SEV is active and populate the SevEsWorkArea
OneTimeCall CheckSevFeatures
- xor edx, edx
- test eax, eax
- jz SevNotActive
- ; If SEV is enabled, C-bit is always above 31
- sub eax, 32
- bts edx, eax
-
-SevNotActive:
+ ; If SEV is enabled, the C-bit position is always above 31.
+ ; The mask will be saved in the EDX and applied during the
+ ; the page table build below.
+ OneTimeCall GetSevCBitMaskAbove31
;
; For OVMF, build some initial page tables at
@@ -105,44 +102,8 @@ pageTableEntriesLoop:
mov [(ecx * 8 + PT_ADDR (0x2000 - 8)) + 4], edx
loop pageTableEntriesLoop
- OneTimeCall IsSevEsEnabled
- test eax, eax
- jz SetCr3
-
- ;
- ; The initial GHCB will live at GHCB_BASE and needs to be un-encrypted.
- ; This requires the 2MB page for this range be broken down into 512 4KB
- ; pages. All will be marked encrypted, except for the GHCB.
- ;
- mov ecx, (GHCB_BASE >> 21)
- mov eax, GHCB_PT_ADDR + PAGE_PDP_ATTR
- mov [ecx * 8 + PT_ADDR (0x2000)], eax
-
- ;
- ; Page Table Entries (512 * 4KB entries => 2MB)
- ;
- mov ecx, 512
-pageTableEntries4kLoop:
- mov eax, ecx
- dec eax
- shl eax, 12
- add eax, GHCB_BASE & 0xFFE0_0000
- add eax, PAGE_4K_PDE_ATTR
- mov [ecx * 8 + GHCB_PT_ADDR - 8], eax
- mov [(ecx * 8 + GHCB_PT_ADDR - 8) + 4], edx
- loop pageTableEntries4kLoop
-
- ;
- ; Clear the encryption bit from the GHCB entry
- ;
- mov ecx, (GHCB_BASE & 0x1F_FFFF) >> 12
- mov [ecx * 8 + GHCB_PT_ADDR + 4], strict dword 0
-
- mov ecx, GHCB_SIZE / 4
- xor eax, eax
-clearGhcbMemoryLoop:
- mov dword[ecx * 4 + GHCB_BASE - 4], eax
- loop clearGhcbMemoryLoop
+ ; Clear the C-bit from the GHCB page if the SEV-ES is enabled.
+ OneTimeCall SevClearPageEncMaskFromGHCBPage
SetCr3:
;
--
2.17.1
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