[PATCH v8 17/32] OvmfPkg/MemEncryptSevLib: add support to validate > 4GB memory in PEI phase


Brijesh Singh
 

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: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Signed-off-by: Brijesh Singh <brijesh.singh@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 eae7a31773a4..a0803e1255dc 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;
@@ -105,6 +108,7 @@ MemEncryptSevSnpPreValidateSystemRam (
{
PHYSICAL_ADDRESS EndAddress;
SNP_PRE_VALIDATED_RANGE OverlapRange;
+ EFI_STATUS Status;

if (!MemEncryptSevSnpIsEnabled ()) {
return;
@@ -112,6 +116,24 @@ 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.
--
2.25.1

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