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| author | Michael Roth <michael.roth@amd.com> | 2024-05-02 13:49:26 +0200 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2024-05-02 12:43:50 +0000 |
| commit | f0ed194236b1fe55199ee82c014b70119ee3f227 (patch) | |
| tree | bfda327ab2be6e0a0d46d5d009402aa238f47170 /OvmfPkg/Sec | |
| parent | fd290ab8628478c62c32c972fc16b86b6c3372ce (diff) | |
| download | edk2-f0ed194236b1fe55199ee82c014b70119ee3f227.zip edk2-f0ed194236b1fe55199ee82c014b70119ee3f227.tar.gz edk2-f0ed194236b1fe55199ee82c014b70119ee3f227.tar.bz2 | |
OvmfPkg: Don't make APIC MMIO accesses with encryption bit set
For the most part, OVMF will clear the encryption bit for MMIO regions,
but there is currently one known exception during SEC when the APIC
base address is accessed via MMIO with the encryption bit set for
SEV-ES/SEV-SNP guests. In the case of SEV-SNP, this requires special
handling on the hypervisor side which may not be available in the
future[1], so make the necessary changes in the SEC-configured page
table to clear the encryption bit for 4K region containing the APIC
base address.
[1] https://lore.kernel.org/lkml/20240208002420.34mvemnzrwwsaesw@amd.com/#t
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jianyong Wu <jianyong.wu@arm.com>
Cc: Anatol Belski <anbelski@linux.microsoft.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to 'OvmfPkg/Sec')
| -rw-r--r-- | OvmfPkg/Sec/AmdSev.c | 58 | ||||
| -rw-r--r-- | OvmfPkg/Sec/AmdSev.h | 14 | ||||
| -rw-r--r-- | OvmfPkg/Sec/SecMain.c | 1 | ||||
| -rw-r--r-- | OvmfPkg/Sec/SecMain.inf | 3 |
4 files changed, 76 insertions, 0 deletions
diff --git a/OvmfPkg/Sec/AmdSev.c b/OvmfPkg/Sec/AmdSev.c index 520b125..89fba2f 100644 --- a/OvmfPkg/Sec/AmdSev.c +++ b/OvmfPkg/Sec/AmdSev.c @@ -8,7 +8,10 @@ **/
#include <Library/BaseLib.h>
+#include <Library/CpuLib.h>
+#include <Library/CpuPageTableLib.h>
#include <Library/DebugLib.h>
+#include <Library/LocalApicLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/BaseMemoryLib.h>
#include <Register/Amd/Ghcb.h>
@@ -301,3 +304,58 @@ SecValidateSystemRam ( MemEncryptSevSnpPreValidateSystemRam (Start, EFI_SIZE_TO_PAGES ((UINTN)(End - Start)));
}
}
+
+/**
+ Map known MMIO regions unencrypted if SEV-ES is active.
+
+ During early booting, page table entries default to having the encryption bit
+ set for SEV-ES/SEV-SNP guests. In cases where there is MMIO to an address, the
+ encryption bit should be cleared. Clear it here for any known MMIO accesses
+ during SEC, which is currently just the APIC base address.
+
+**/
+VOID
+SecMapApicBaseUnencrypted (
+ VOID
+ )
+{
+ PHYSICAL_ADDRESS Cr3;
+ UINT64 ApicAddress;
+ VOID *Buffer;
+ UINTN BufferSize;
+ IA32_MAP_ATTRIBUTE MapAttribute;
+ IA32_MAP_ATTRIBUTE MapMask;
+ RETURN_STATUS Status;
+
+ if (!SevEsIsEnabled ()) {
+ return;
+ }
+
+ ApicAddress = (UINT64)GetLocalApicBaseAddress ();
+ Buffer = (VOID *)(UINTN)FixedPcdGet32 (PcdOvmfSecApicPageTableBase);
+ Cr3 = AsmReadCr3 ();
+
+ MapAttribute.Uint64 = ApicAddress;
+ MapAttribute.Bits.Present = 1;
+ MapAttribute.Bits.ReadWrite = 1;
+ MapMask.Uint64 = MAX_UINT64;
+ BufferSize = SIZE_4KB;
+
+ Status = PageTableMap (
+ (UINTN *)&Cr3,
+ Paging4Level,
+ Buffer,
+ &BufferSize,
+ ApicAddress,
+ SIZE_4KB,
+ &MapAttribute,
+ &MapMask,
+ NULL
+ );
+ if (RETURN_ERROR (Status)) {
+ DEBUG ((DEBUG_ERROR, "Failed to map APIC MMIO region as unencrypted: %d\n", Status));
+ ASSERT (FALSE);
+ }
+
+ CpuFlushTlb ();
+}
diff --git a/OvmfPkg/Sec/AmdSev.h b/OvmfPkg/Sec/AmdSev.h index f758770..c5ab0d5 100644 --- a/OvmfPkg/Sec/AmdSev.h +++ b/OvmfPkg/Sec/AmdSev.h @@ -91,4 +91,18 @@ SevSnpIsEnabled ( VOID
);
+/**
+ Map MMIO regions unencrypted if SEV-ES is active.
+
+ During early booting, page table entries default to having the encryption bit
+ set for SEV-ES/SEV-SNP guests. In cases where there is MMIO to an address, the
+ encryption bit should be cleared. Clear it here for any known MMIO accesses
+ during SEC, which is currently just the APIC base address.
+
+**/
+VOID
+SecMapApicBaseUnencrypted (
+ VOID
+ );
+
#endif
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c index a30d4ce..60dfa61 100644 --- a/OvmfPkg/Sec/SecMain.c +++ b/OvmfPkg/Sec/SecMain.c @@ -938,6 +938,7 @@ SecCoreStartupWithStack ( // interrupts before initializing the Debug Agent and the debug timer is
// enabled.
//
+ SecMapApicBaseUnencrypted ();
InitializeApicTimer (0, MAX_UINT32, TRUE, 5);
DisableApicTimerInterrupt ();
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf index dca932a..88c2d3f 100644 --- a/OvmfPkg/Sec/SecMain.inf +++ b/OvmfPkg/Sec/SecMain.inf @@ -55,6 +55,7 @@ MemEncryptSevLib
CpuExceptionHandlerLib
CcProbeLib
+ CpuPageTableLib
[Ppis]
gEfiTemporaryRamSupportPpiGuid # PPI ALWAYS_PRODUCED
@@ -83,6 +84,8 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase
gUefiOvmfPkgTokenSpaceGuid.PcdTdxAcceptPageSize
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableBase
+ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecApicPageTableSize
[FeaturePcd]
gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
|