mirror of https://github.com/acidanthera/audk.git
OvmfPkg: Create a GHCB page for use during Sec phase
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198 A GHCB page is needed during the Sec phase, so this new page must be created. Since the #VC exception handler routines assume that a per-CPU variable area is immediately after the GHCB, this per-CPU variable area must also be created. Since the GHCB must be marked as an un-encrypted, or shared, page, an additional pagetable page is required to break down the 2MB region where the GHCB page lives into 4K pagetable entries. Create a new entry in the OVMF memory layout for the new page table page and for the SEC GHCB and per-CPU variable pages. After breaking down the 2MB page, update the GHCB page table entry to remove the encryption mask. The GHCB page will be used by the SEC #VC exception handler. The #VC exception handler will fill in the necessary fields of the GHCB and exit to the hypervisor using the VMGEXIT instruction. The hypervisor then accesses the GHCB in order to perform the requested function. Four new fixed PCDs are needed to support the SEC GHCB page: - PcdOvmfSecGhcbBase UINT32 value that is the base address of the GHCB used during the SEC phase. - PcdOvmfSecGhcbSize UINT32 value that is the size, in bytes, of the GHCB area used during the SEC phase. - PcdOvmfSecGhcbPageTableBase UINT32 value that is address of a page table page used to break down the 2MB page into 512 4K pages. - PcdOvmfSecGhcbPageTableSize UINT32 value that is the size, in bytes, of the page table page. Cc: Jordan Justen <jordan.l.justen@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Tom Lendacky
mergify[bot]
parent
cf845a749a
commit
6995a1b79b
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@ -294,6 +294,15 @@
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## Number of page frames to use for storing grant table entries.
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gUefiOvmfPkgTokenSpaceGuid.PcdXenGrantFrames|4|UINT32|0x33
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## Specify the extra page table needed to mark the GHCB as unencrypted.
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# The value should be a multiple of 4KB for each.
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase|0x0|UINT32|0x3e
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize|0x0|UINT32|0x3f
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## The base address of the SEC GHCB page used by SEV-ES.
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase|0|UINT32|0x40
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize|0|UINT32|0x41
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[PcdsDynamic, PcdsDynamicEx]
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gUefiOvmfPkgTokenSpaceGuid.PcdEmuVariableEvent|0|UINT64|2
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfFlashVariablesEnable|FALSE|BOOLEAN|0x10
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@ -76,6 +76,12 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageBase|gUefiOvmfPkgTokenSpaceGuid.
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0x007000|0x001000
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gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize
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0x008000|0x001000
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize
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0x009000|0x002000
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize
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0x010000|0x010000
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
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@ -21,6 +21,11 @@ BITS 32
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%define PAGE_2M_MBO 0x080
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%define PAGE_2M_PAT 0x01000
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%define PAGE_4K_PDE_ATTR (PAGE_ACCESSED + \
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PAGE_DIRTY + \
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PAGE_READ_WRITE + \
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PAGE_PRESENT)
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%define PAGE_2M_PDE_ATTR (PAGE_2M_MBO + \
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PAGE_ACCESSED + \
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PAGE_DIRTY + \
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@ -75,6 +80,37 @@ NoSev:
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SevExit:
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OneTimeCallRet CheckSevFeature
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; Check if Secure Encrypted Virtualization - Encrypted State (SEV-ES) feature
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; is enabled.
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;
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; Modified: EAX, EBX, ECX
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;
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; If SEV-ES is enabled then EAX will be non-zero.
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; If SEV-ES is disabled then EAX will be zero.
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;
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CheckSevEsFeature:
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xor eax, eax
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; SEV-ES can't be enabled if SEV isn't, so first check the encryption
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; mask.
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test edx, edx
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jz NoSevEs
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; Save current value of encryption mask
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mov ebx, edx
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; Check if SEV-ES is enabled
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; MSR_0xC0010131 - Bit 1 (SEV-ES enabled)
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mov ecx, 0xc0010131
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rdmsr
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and eax, 2
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; Restore encryption mask
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mov edx, ebx
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NoSevEs:
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OneTimeCallRet CheckSevEsFeature
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;
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; Modified: EAX, EBX, ECX, EDX
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;
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@ -139,6 +175,46 @@ pageTableEntriesLoop:
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mov [(ecx * 8 + PT_ADDR (0x2000 - 8)) + 4], edx
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loop pageTableEntriesLoop
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OneTimeCall CheckSevEsFeature
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test eax, eax
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jz SetCr3
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;
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; The initial GHCB will live at GHCB_BASE and needs to be un-encrypted.
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; This requires the 2MB page for this range be broken down into 512 4KB
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; pages. All will be marked encrypted, except for the GHCB.
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;
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mov ecx, (GHCB_BASE >> 21)
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mov eax, GHCB_PT_ADDR + PAGE_PDP_ATTR
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mov [ecx * 8 + PT_ADDR (0x2000)], eax
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;
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; Page Table Entries (512 * 4KB entries => 2MB)
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;
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mov ecx, 512
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pageTableEntries4kLoop:
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mov eax, ecx
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dec eax
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shl eax, 12
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add eax, GHCB_BASE & 0xFFE0_0000
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add eax, PAGE_4K_PDE_ATTR
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mov [ecx * 8 + GHCB_PT_ADDR - 8], eax
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mov [(ecx * 8 + GHCB_PT_ADDR - 8) + 4], edx
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loop pageTableEntries4kLoop
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;
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; Clear the encryption bit from the GHCB entry
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;
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mov ecx, (GHCB_BASE & 0x1F_FFFF) >> 12
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mov [ecx * 8 + GHCB_PT_ADDR + 4], strict dword 0
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mov ecx, GHCB_SIZE / 4
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xor eax, eax
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clearGhcbMemoryLoop:
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mov dword[ecx * 4 + GHCB_BASE - 4], eax
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loop clearGhcbMemoryLoop
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SetCr3:
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;
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; Set CR3 now that the paging structures are available
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;
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@ -26,6 +26,7 @@
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[Packages]
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OvmfPkg/OvmfPkg.dec
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MdePkg/MdePkg.dec
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MdeModulePkg/MdeModulePkg.dec
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UefiCpuPkg/UefiCpuPkg.dec
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[BuildOptions]
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@ -33,5 +34,9 @@
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*_*_X64_NASMB_FLAGS = -I$(WORKSPACE)/UefiCpuPkg/ResetVector/Vtf0/
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[Pcd]
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBase
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbSize
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableBase
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbPageTableSize
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
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gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesSize
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@ -53,8 +53,25 @@
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%error "This implementation inherently depends on PcdOvmfSecPageTablesSize"
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%endif
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%if (FixedPcdGet32 (PcdOvmfSecGhcbPageTableSize) != 0x1000)
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%error "This implementation inherently depends on PcdOvmfSecGhcbPageTableSize"
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%endif
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%if (FixedPcdGet32 (PcdOvmfSecGhcbSize) != 0x2000)
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%error "This implementation inherently depends on PcdOvmfSecGhcbSize"
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%endif
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%if ((FixedPcdGet32 (PcdOvmfSecGhcbBase) >> 21) != \
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((FixedPcdGet32 (PcdOvmfSecGhcbBase) + FixedPcdGet32 (PcdOvmfSecGhcbSize) - 1) >> 21))
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%error "This implementation inherently depends on PcdOvmfSecGhcbBase not straddling a 2MB boundary"
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%endif
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%define PT_ADDR(Offset) (FixedPcdGet32 (PcdOvmfSecPageTablesBase) + (Offset))
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%include "Ia32/Flat32ToFlat64.asm"
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%define GHCB_PT_ADDR (FixedPcdGet32 (PcdOvmfSecGhcbPageTableBase))
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%define GHCB_BASE (FixedPcdGet32 (PcdOvmfSecGhcbBase))
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%define GHCB_SIZE (FixedPcdGet32 (PcdOvmfSecGhcbSize))
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%include "Ia32/PageTables64.asm"
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%endif
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