BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
The initial page built during the SEC phase is used by the MemEncryptSevSnpValidateSystemRam() for the system RAM validation. The page validation process requires using the PVALIDATE instruction; the instruction accepts a virtual address of the memory region that needs to be validated. If hardware encounters a page table walk failure (due to page-not-present) then it raises #GP. The initial page table built in SEC phase address up to 4GB. Add an internal function to extend the page table to cover > 4GB. The function builds 1GB entries in the page table for access > 4GB. This will provide the support to call PVALIDATE instruction for the virtual address > 4GB in PEI phase. Cc: James Bottomley <j...@linux.ibm.com> Cc: Min Xu <min.m...@intel.com> Cc: Jiewen Yao <jiewen....@intel.com> Cc: Tom Lendacky <thomas.lenda...@amd.com> Cc: Jordan Justen <jordan.l.jus...@intel.com> Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org> Cc: Laszlo Ersek <ler...@redhat.com> Cc: Erdem Aktas <erdemak...@google.com> Signed-off-by: Brijesh Singh <brijesh.si...@amd.com> --- .../BaseMemEncryptSevLib/X64/VirtualMemory.h | 19 +++ .../X64/PeiDxeVirtualMemory.c | 115 ++++++++++++++++++ .../X64/PeiSnpSystemRamValidate.c | 22 ++++ 3 files changed, 156 insertions(+) diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.h b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.h index 21bbbd1c4f9c..aefef68c30c0 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.h +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.h @@ -143,4 +143,23 @@ InternalMemEncryptSevClearMmioPageEncMask ( IN PHYSICAL_ADDRESS PhysicalAddress, IN UINTN Length ); + +/** + Create 1GB identity mapping for the specified virtual address range. + + @param[in] Cr3BaseAddress Cr3 Base Address (if zero then use + current CR3) + @param[in] VirtualAddress Virtual address + @param[in] Length Length of virtual address range + + @retval RETURN_INVALID_PARAMETER Number of pages is zero. + +**/ +RETURN_STATUS +EFIAPI +InternalMemEncryptSevCreateIdentityMap1G ( + IN PHYSICAL_ADDRESS Cr3BaseAddress, + IN PHYSICAL_ADDRESS PhysicalAddress, + IN UINTN Length + ); #endif diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c index c696745f9d26..f146f6d61cc5 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c @@ -536,6 +536,121 @@ EnableReadOnlyPageWriteProtect ( AsmWriteCr0 (AsmReadCr0() | BIT16); } +RETURN_STATUS +EFIAPI +InternalMemEncryptSevCreateIdentityMap1G ( + IN PHYSICAL_ADDRESS Cr3BaseAddress, + IN PHYSICAL_ADDRESS PhysicalAddress, + IN UINTN Length + ) +{ + PAGE_MAP_AND_DIRECTORY_POINTER *PageMapLevel4Entry; + PAGE_TABLE_1G_ENTRY *PageDirectory1GEntry; + UINT64 PgTableMask; + UINT64 AddressEncMask; + BOOLEAN IsWpEnabled; + RETURN_STATUS Status; + + // + // Set PageMapLevel4Entry to suppress incorrect compiler/analyzer warnings. + // + PageMapLevel4Entry = NULL; + + DEBUG (( + DEBUG_VERBOSE, + "%a:%a: Cr3Base=0x%Lx Physical=0x%Lx Length=0x%Lx\n", + gEfiCallerBaseName, + __FUNCTION__, + Cr3BaseAddress, + PhysicalAddress, + (UINT64)Length + )); + + if (Length == 0) { + return RETURN_INVALID_PARAMETER; + } + + // + // Check if we have a valid memory encryption mask + // + AddressEncMask = InternalGetMemEncryptionAddressMask (); + if (!AddressEncMask) { + return RETURN_ACCESS_DENIED; + } + + PgTableMask = AddressEncMask | EFI_PAGE_MASK; + + + // + // Make sure that the page table is changeable. + // + IsWpEnabled = IsReadOnlyPageWriteProtected (); + if (IsWpEnabled) { + DisableReadOnlyPageWriteProtect (); + } + + Status = EFI_SUCCESS; + + while (Length) + { + // + // If Cr3BaseAddress is not specified then read the current CR3 + // + if (Cr3BaseAddress == 0) { + Cr3BaseAddress = AsmReadCr3(); + } + + PageMapLevel4Entry = (VOID*) (Cr3BaseAddress & ~PgTableMask); + PageMapLevel4Entry += PML4_OFFSET(PhysicalAddress); + if (!PageMapLevel4Entry->Bits.Present) { + DEBUG (( + DEBUG_ERROR, + "%a:%a: bad PML4 for Physical=0x%Lx\n", + gEfiCallerBaseName, + __FUNCTION__, + PhysicalAddress + )); + Status = RETURN_NO_MAPPING; + goto Done; + } + + PageDirectory1GEntry = (VOID *)( + (PageMapLevel4Entry->Bits.PageTableBaseAddress << + 12) & ~PgTableMask + ); + PageDirectory1GEntry += PDP_OFFSET(PhysicalAddress); + if (!PageDirectory1GEntry->Bits.Present) { + PageDirectory1GEntry->Bits.Present = 1; + PageDirectory1GEntry->Bits.MustBe1 = 1; + PageDirectory1GEntry->Bits.MustBeZero = 0; + PageDirectory1GEntry->Bits.ReadWrite = 1; + PageDirectory1GEntry->Uint64 |= (UINT64)PhysicalAddress | AddressEncMask; + } + + if (Length <= BIT30) { + Length = 0; + } else { + Length -= BIT30; + } + + PhysicalAddress += BIT30; + } + + // + // Flush TLB + // + CpuFlushTlb(); + +Done: + // + // Restore page table write protection, if any. + // + if (IsWpEnabled) { + EnableReadOnlyPageWriteProtect (); + } + + return Status; +} /** This function either sets or clears memory encryption bit for the memory diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c index 3e692a3b869d..69ffb79633c4 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c @@ -10,9 +10,12 @@ #include <Uefi/UefiBaseType.h> #include <Library/BaseLib.h> +#include <Library/PcdLib.h> +#include <Library/DebugLib.h> #include <Library/MemEncryptSevLib.h> #include "SnpPageStateChange.h" +#include "VirtualMemory.h" typedef struct { UINT64 StartAddress; @@ -68,6 +71,7 @@ MemEncryptSevSnpPreValidateSystemRam ( { PHYSICAL_ADDRESS EndAddress; SNP_PRE_VALIDATED_RANGE OverlapRange; + EFI_STATUS Status; if (!MemEncryptSevSnpIsEnabled ()) { return; @@ -75,6 +79,24 @@ MemEncryptSevSnpPreValidateSystemRam ( EndAddress = BaseAddress + EFI_PAGES_TO_SIZE (NumPages); + // + // The page table used in PEI can address up to 4GB memory. If we are asked to + // validate a range above the 4GB, then create an identity mapping so that the + // PVALIDATE instruction can execute correctly. If the page table entry is not + // present then PVALIDATE will #GP. + // + if (BaseAddress >= SIZE_4GB) { + Status = InternalMemEncryptSevCreateIdentityMap1G ( + 0, + BaseAddress, + EFI_PAGES_TO_SIZE (NumPages) + ); + if (EFI_ERROR (Status)) { + ASSERT (FALSE); + CpuDeadLoop (); + } + } + while (BaseAddress < EndAddress) { // // Check if the range overlaps with the pre-validated ranges. -- 2.17.1 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#75731): https://edk2.groups.io/g/devel/message/75731 Mute This Topic: https://groups.io/mt/83113778/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-