From 2c000372cab80ab68a8672138c8d0f5cb1ae43d9 Mon Sep 17 00:00:00 2001
From: Ashish Kalra <ashish.kalra@amd.com>
Date: Tue, 5 Apr 2022 16:23:53 +0000
Subject: [PATCH 2/9] OvmfPkg/BaseMemEncryptLib: Hypercall API for page
encryption state change
cherry-picked from https://patchew.org/EDK2/cover.1629380011.git.ashish.kalra@amd.com .
Add API to issue hypercall on page encryption state change.
By default all the SEV guest memory regions are considered encrypted,
if a guest changes the encryption attribute of the page (e.g mark a
page as decrypted) then notify hypervisor. Hypervisor will need to
track the unencrypted pages. The information will be used during
guest live migration, guest page migration and guest debugging.
This hypercall is used to notify hypervisor when the page's
encryption state changes.
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
OvmfPkg/Include/Library/MemEncryptSevLib.h | 52 +++++++++++++++
.../DxeMemEncryptSevLib.inf | 1 +
.../Ia32/MemEncryptSevLib.c | 27 ++++++++
.../PeiMemEncryptSevLib.inf | 1 +
.../SecMemEncryptSevLibInternal.c | 20 ++++++
.../X64/AsmHelperStub.nasm | 33 ++++++++++
.../X64/MemEncryptSevLib.c | 66 +++++++++++++++++++
7 files changed, 200 insertions(+)
create mode 100644 OvmfPkg/Library/BaseMemEncryptSevLib/X64/AsmHelperStub.nasm
@@ -240,4 +240,56 @@ MemEncryptSevSnpPreValidateSystemRam (
IN UINTN NumPages
);
+/**
+ This hypercall is used to notify hypervisor when the page's encryption
+ state changes.
+
+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Pages Number of pages in memory region.
+ @param[in] IsEncrypted Encrypted or Decrypted.
+
+ @retval RETURN_SUCCESS Hypercall returned success.
+ @retval RETURN_UNSUPPORTED Hypercall not supported.
+ @retval RETURN_NO_MAPPING Hypercall returned error.
+**/
+RETURN_STATUS
+EFIAPI
+SetMemoryEncDecHypercall3 (
+ IN UINTN PhysicalAddress,
+ IN UINTN Pages,
+ IN BOOLEAN IsEncrypted
+ );
+
+#define KVM_HC_MAP_GPA_RANGE 12
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_4K 0
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_2M BIT0
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_1G BIT1
+#define KVM_MAP_GPA_RANGE_ENC_STATE(n) ((n) << 4)
+#define KVM_MAP_GPA_RANGE_ENCRYPTED KVM_MAP_GPA_RANGE_ENC_STATE(1)
+#define KVM_MAP_GPA_RANGE_DECRYPTED KVM_MAP_GPA_RANGE_ENC_STATE(0)
+
+/**
+ Interface exposed by the ASM implementation of the core hypercall
+
+ @param[in] HypercallNum KVM_HC_MAP_GPA_RANGE hypercall.
+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Pages Number of pages in memory region.
+ @param[in] Attributes Bits 3:0 - preferred page size encoding,
+ 0 = 4kb, 1 = 2mb, 2 = 1gb, etc...
+ Bit 4 - plaintext = 0, encrypted = 1
+ Bits 63:5 - reserved (must be zero)
+
+ @retval Hypercall returned status.
+**/
+UINTN
+EFIAPI
+SetMemoryEncDecHypercall3AsmStub (
+ IN UINTN HypercallNum,
+ IN UINTN PhysicalAddress,
+ IN UINTN Pages,
+ IN UINTN Attributes
+ );
+
#endif // _MEM_ENCRYPT_SEV_LIB_H_
@@ -40,6 +40,7 @@
X64/SnpPageStateChangeInternal.c
X64/VirtualMemory.c
X64/VirtualMemory.h
+ X64/AsmHelperStub.nasm
[Sources.IA32]
Ia32/MemEncryptSevLib.c
@@ -153,3 +153,30 @@ MemEncryptSevSnpPreValidateSystemRam (
{
ASSERT (FALSE);
}
+
+/**
+ This hyercall is used to notify hypervisor when the page's encryption
+ state changes.
+
+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Pages Number of Pages in the memory region.
+ @param[in] IsEncrypted Encrypted or Decrypted.
+
+ @retval RETURN_SUCCESS Hypercall returned success.
+ @retval RETURN_UNSUPPORTED Hypercall not supported.
+ @retval RETURN_NO_MAPPING Hypercall returned error.
+**/
+RETURN_STATUS
+EFIAPI
+SetMemoryEncDecHypercall3 (
+ IN UINTN PhysicalAddress,
+ IN UINTN Pages,
+ IN BOOLEAN IsEncrypted
+ )
+{
+ //
+ // Memory encryption bit is not accessible in 32-bit mode
+ //
+ return RETURN_UNSUPPORTED;
+}
@@ -40,6 +40,7 @@
X64/SnpPageStateChangeInternal.c
X64/VirtualMemory.c
X64/VirtualMemory.h
+ X64/AsmHelperStub.nasm
[Sources.IA32]
Ia32/MemEncryptSevLib.c
@@ -139,6 +139,26 @@ MemEncryptSevLiveMigrationIsEnabled (
return FALSE;
}
+/**
+ Interface exposed by the ASM implementation of the core hypercall
+
+ @retval Hypercall returned status.
+**/
+UINTN
+EFIAPI
+SetMemoryEncDecHypercall3AsmStub (
+ IN UINTN HypercallNum,
+ IN UINTN PhysicalAddress,
+ IN UINTN Pages,
+ IN UINTN Attributes
+ )
+{
+ //
+ // Not used in SEC phase.
+ //
+ return RETURN_UNSUPPORTED;
+}
+
/**
Returns the SEV encryption mask.
new file mode 100644
@@ -0,0 +1,33 @@
+/** @file
+
+ ASM helper stub to invoke hypercall
+
+ Copyright (c) 2021, AMD Incorporated. All rights reserved.<BR>
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+DEFAULT REL
+SECTION .text
+
+; UINTN
+; EFIAPI
+; SetMemoryEncDecHypercall3AsmStub (
+; IN UINTN HypercallNum,
+; IN UINTN Arg1,
+; IN UINTN Arg2,
+; IN UINTN Arg3
+; );
+global ASM_PFX(SetMemoryEncDecHypercall3AsmStub)
+ASM_PFX(SetMemoryEncDecHypercall3AsmStub):
+ ; UEFI calling conventions require RBX to
+ ; be nonvolatile/callee-saved.
+ push rbx
+ mov rax, rcx ; Copy HypercallNumber to rax
+ mov rbx, rdx ; Copy Arg1 to the register expected by KVM
+ mov rcx, r8 ; Copy Arg2 to register expected by KVM
+ mov rdx, r9 ; Copy Arg3 to register expected by KVM
+ vmmcall ; Call VMMCALL
+ pop rbx
+ ret
@@ -142,3 +142,69 @@ MemEncryptSevClearMmioPageEncMask (
EFI_PAGES_TO_SIZE (NumPages)
);
}
+
+/**
+ This hyercall is used to notify hypervisor when the page's encryption
+ state changes.
+
+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Pages Number of Pages in the memory region.
+ @param[in] IsEncrypted Encrypted or Decrypted.
+
+ @retval RETURN_SUCCESS Hypercall returned success.
+ @retval RETURN_UNSUPPORTED Hypercall not supported.
+ @retval RETURN_NO_MAPPING Hypercall returned error.
+**/
+RETURN_STATUS
+EFIAPI
+SetMemoryEncDecHypercall3 (
+ IN UINTN PhysicalAddress,
+ IN UINTN Pages,
+ IN BOOLEAN IsEncrypted
+ )
+{
+ RETURN_STATUS Ret;
+ UINTN Error;
+ UINTN EncryptState;
+
+ Ret = RETURN_UNSUPPORTED;
+
+ if (MemEncryptSevLiveMigrationIsEnabled ()) {
+ Ret = RETURN_SUCCESS;
+ //
+ // The encryption bit is set/clear on the smallest page size, hence
+ // use the 4k page size in MAP_GPA_RANGE hypercall below.
+ //
+ // Also, when the GCD map is being walked and the c-bit being cleared
+ // from MMIO and NonExistent memory spaces, the physical address
+ // range being passed may not be page-aligned and adding an assert
+ // here prevents booting. Hence, rounding it down when calling
+ // SetMemoryEncDecHypercall3AsmStub below.
+ //
+
+ EncryptState = IsEncrypted ? KVM_MAP_GPA_RANGE_ENCRYPTED :
+ KVM_MAP_GPA_RANGE_DECRYPTED;
+
+ Error = SetMemoryEncDecHypercall3AsmStub (
+ KVM_HC_MAP_GPA_RANGE,
+ PhysicalAddress & ~EFI_PAGE_MASK,
+ Pages,
+ KVM_MAP_GPA_RANGE_PAGE_SZ_4K | EncryptState
+ );
+
+ if (Error != 0) {
+ DEBUG ((
+ DEBUG_ERROR,
+ "SetMemoryEncDecHypercall3 failed, Phys = %x, Pages = %d, Err = %Ld\n",
+ PhysicalAddress,
+ Pages,
+ (INT64)Error
+ ));
+
+ Ret = RETURN_NO_MAPPING;
+ }
+ }
+
+ return Ret;
+}
--
2.25.1