Re: [PATCH v4 1/4] OvmfPkg/MemEncryptHypercallLib: add library to support SEV hypercalls.


Brijesh Singh
 

On 6/22/2021 2:47 PM, Brijesh Singh wrote:


On 6/21/2021 8:56 AM, Ashish Kalra wrote:
From: Ashish Kalra <ashish.kalra@amd.com>

Add SEV and SEV-ES hypercall abstraction library to support SEV Page
encryption/deceryption status hypercalls for SEV and SEV-ES guests.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Remove this newline.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
Maintainers.txt | 2 +
OvmfPkg/Include/Library/MemEncryptHypercallLib.h | 43 ++++++++
OvmfPkg/Library/MemEncryptHypercallLib/Ia32/MemEncryptHypercallLib.c | 37 +++++++
OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf | 42 ++++++++
OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm | 28 ++++++
OvmfPkg/Library/MemEncryptHypercallLib/X64/MemEncryptHypercallLib.c | 105 ++++++++++++++++++++
OvmfPkg/OvmfPkgIa32.dsc | 1 +
OvmfPkg/OvmfPkgIa32X64.dsc | 1 +
OvmfPkg/OvmfPkgX64.dsc | 1 +
OvmfPkg/OvmfXen.dsc | 1 +
10 files changed, 261 insertions(+)

diff --git a/Maintainers.txt b/Maintainers.txt
index ea54e0b7e9..8ecc8464ba 100644
--- a/Maintainers.txt
+++ b/Maintainers.txt
@@ -449,8 +449,10 @@ F: OvmfPkg/AmdSev/
F: OvmfPkg/AmdSevDxe/
F: OvmfPkg/Include/Guid/ConfidentialComputingSecret.h
F: OvmfPkg/Include/Library/MemEncryptSevLib.h
+F: OvmfPkg/Include/Library/MemEncryptHypercallLib.h
F: OvmfPkg/IoMmuDxe/AmdSevIoMmu.*
F: OvmfPkg/Library/BaseMemEncryptSevLib/
+F: OvmfPkg/Library/MemEncryptHypercallLib/
F: OvmfPkg/Library/PlatformBootManagerLibGrub/
F: OvmfPkg/Library/VmgExitLib/
F: OvmfPkg/PlatformPei/AmdSev.c
diff --git a/OvmfPkg/Include/Library/MemEncryptHypercallLib.h b/OvmfPkg/Include/Library/MemEncryptHypercallLib.h
new file mode 100644
index 0000000000..b241a189b6
--- /dev/null
+++ b/OvmfPkg/Include/Library/MemEncryptHypercallLib.h
@@ -0,0 +1,43 @@
+/** @file
+
+ Define Secure Encrypted Virtualization (SEV) hypercall library.
+
+ Copyright (c) 2020, AMD Incorporated. All rights reserved.<BR>
^^^^
2021

+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef _MEM_ENCRYPT_HYPERCALL_LIB_H_
+#define _MEM_ENCRYPT_HYPERCALL_LIB_H_
+
+#include <Base.h>
+
+#define KVM_HC_MAP_GPA_RANGE 12
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_4K 0
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_2M (1 << 0)
+#define KVM_MAP_GPA_RANGE_PAGE_SZ_1G (1 << 1)
+#define KVM_MAP_GPA_RANGE_ENC_STAT(n) ((n) << 4)
+#define KVM_MAP_GPA_RANGE_ENCRYPTED KVM_MAP_GPA_RANGE_ENC_STAT(1)
+#define KVM_MAP_GPA_RANGE_DECRYPTED KVM_MAP_GPA_RANGE_ENC_STAT(0)
+
+/**
+ This hyercall is used to notify hypervisor when a page is marked as
+ 'decrypted' (i.e C-bit removed).
+
Looking at the function signature it seems this routine is used for both set
and clear. Please update the comment accordingly.


+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Length The length of memory region
+ @param[in] Mode SetCBit or ClearCBit
+
+**/
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3 (
+ IN UINTN PhysicalAddress,
+ IN UINTN Length,
+ IN UINTN Mode
+ );
+
+#endif
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/Ia32/MemEncryptHypercallLib.c b/OvmfPkg/Library/MemEncryptHypercallLib/Ia32/MemEncryptHypercallLib.c
new file mode 100644
index 0000000000..2e73d47ee6
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/Ia32/MemEncryptHypercallLib.c
@@ -0,0 +1,37 @@
+/** @file
+
+ Secure Encrypted Virtualization (SEV) hypercall helper library
+
+ Copyright (c) 2020, AMD Incorporated. All rights reserved.<BR>
^^^^
2021

+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Uefi.h>
+#include <Uefi/UefiBaseType.h>
+#include <Library/BaseLib.h>
+
+/**
+ This hyercall is used to notify hypervisor when a page is marked as
+ 'decrypted' (i.e C-bit removed).
+
+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Length The length of memory region
+ @param[in] Mode SetCBit or ClearCBit
+
+**/
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3 (
+ IN PHYSICAL_ADDRESS PhysicalAddress,
+ IN UINTN Pages,
+ IN UINTN Mode
+ )
+{
+ //
+ // Memory encryption bit is not accessible in 32-bit mode
+ //
+}
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf b/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
new file mode 100644
index 0000000000..a77d58a7e6
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
@@ -0,0 +1,42 @@
+## @file
+# Library provides the hypervisor helper functions for SEV guest
+#
+# Copyright (c) 2020 Advanced Micro Devices. All rights reserved.<BR>
^^^^
2021
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#
+##
+
+[Defines]
+ INF_VERSION = 1.25
+ BASE_NAME = MemEncryptHypercallLib
+ FILE_GUID = 86f2501e-f128-45f3-91c4-3cff31656ca8
+ MODULE_TYPE = BASE
+ VERSION_STRING = 1.0
+ LIBRARY_CLASS = MemEncryptHypercallLib
+
+#
+# The following information is for reference only and not required by the build
+# tools.
+#
+# VALID_ARCHITECTURES = IA32 X64
+#
+
+[Packages]
+ MdeModulePkg/MdeModulePkg.dec
+ MdePkg/MdePkg.dec
+ UefiCpuPkg/UefiCpuPkg.dec
+ OvmfPkg/OvmfPkg.dec
+
+[Sources.X64]
+ X64/MemEncryptHypercallLib.c
+ X64/AsmHelperStub.nasm
+
+[Sources.IA32]
+ Ia32/MemEncryptHypercallLib.c
+
+[LibraryClasses]
+ BaseLib
+ DebugLib
+ VmgExitLib
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm b/OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm
new file mode 100644
index 0000000000..f29b96f9b0
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/X64/AsmHelperStub.nasm
@@ -0,0 +1,28 @@
+DEFAULT REL
+SECTION .text
+
+; VOID
+; EFIAPI
+; SetMemoryEncDecHypercall3AsmStub (
+; IN UINT HypercallNum,
+; IN INTN Arg1,
+; IN INTN Arg2,
+; IN INTN Arg3
+; );
+global ASM_PFX(SetMemoryEncDecHypercall3AsmStub)
+ASM_PFX(SetMemoryEncDecHypercall3AsmStub):
+ ; UEFI calling conventions require RBX to
+ ; be nonvolatile/callee-saved.
+ push rbx
+ ; Copy HypercallNumber to rax
+ mov rax, rcx
+ ; Copy Arg1 to the register expected by KVM
+ mov rbx, rdx
+ ; Copy Arg2 to register expected by KVM
+ mov rcx, r8
+ ; Copy Arg2 to register expected by KVM
+ mov rdx, r9
+ ; Call VMMCALL
+ vmmcall
+ pop rbx
+ ret
diff --git a/OvmfPkg/Library/MemEncryptHypercallLib/X64/MemEncryptHypercallLib.c b/OvmfPkg/Library/MemEncryptHypercallLib/X64/MemEncryptHypercallLib.c
new file mode 100644
index 0000000000..1c09ea012b
--- /dev/null
+++ b/OvmfPkg/Library/MemEncryptHypercallLib/X64/MemEncryptHypercallLib.c
@@ -0,0 +1,105 @@
+/** @file
+
+ Secure Encrypted Virtualization (SEV) hypercall helper library
+
+ Copyright (c) 2020, AMD Incorporated. All rights reserved.<BR>
^^^^
2021
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Uefi.h>
+#include <Uefi/UefiBaseType.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/VmgExitLib.h>
+#include <Register/Amd/Ghcb.h>
+#include <Register/Amd/Msr.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/MemEncryptHypercallLib.h>
+
+//
+// Interface exposed by the ASM implementation of the core hypercall
+//
+//
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3AsmStub (
+ IN UINTN HypercallNum,
+ IN UINTN PhysicalAddress,
+ IN UINTN Length,
+ IN UINTN Mode
+ );
+
The function signature does not match with documented signature. Fix the
SetMemoryEncDecHypercall3AsmStub() documented in AsmHelperStub.nasm to use
UINTN.


+STATIC
+VOID
+GhcbSetRegValid (
+ IN OUT GHCB *Ghcb,
+ IN GHCB_REGISTER Reg
+ )
+{
+ UINT32 RegIndex;
+ UINT32 RegBit;
+
+ RegIndex = Reg / 8;
+ RegBit = Reg & 0x07;
+
+ Ghcb->SaveArea.ValidBitmap[RegIndex] |= (1 << RegBit);
+}
+
This looks similar to VmgSetOffsetValid().

+/**
+ This hyercall is used to notify hypervisor when a page is marked as
+ 'decrypted' (i.e C-bit removed).
+Please update the comment.
+ @param[in] PhysicalAddress The physical address that is the start address
+ of a memory region.
+ @param[in] Length The length of memory region
+ @param[in] Mode SetCBit or ClearCBit
+
+**/
+
+VOID
+EFIAPI
+SetMemoryEncDecHypercall3 (
+ IN PHYSICAL_ADDRESS PhysicalAddress,
+ IN UINTN Pages,
+ IN UINTN Mode
+ )
+{
+ if (MemEncryptSevEsIsEnabled ()) {> + MSR_SEV_ES_GHCB_REGISTER Msr;
+ GHCB *Ghcb;
+ BOOLEAN InterruptState;
+ UINT64 Status;
+
+ Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+ Ghcb = Msr.Ghcb;
+
+ VmgInit (Ghcb, &InterruptState);
+
+ Ghcb->SaveArea.Rax = KVM_HC_MAP_GPA_RANGE;
+ GhcbSetRegValid (Ghcb, GhcbRax);
+ Ghcb->SaveArea.Rbx = PhysicalAddress;
+ GhcbSetRegValid (Ghcb, GhcbRbx);
+ Ghcb->SaveArea.Rcx = Pages;
+ GhcbSetRegValid (Ghcb, GhcbRcx);
+ Ghcb->SaveArea.Rdx = Mode;
+ GhcbSetRegValid (Ghcb, GhcbRdx);
+ Ghcb->SaveArea.Cpl = AsmReadCs() & 0x3;
+ GhcbSetRegValid (Ghcb, GhcbCpl);
+
+ Status = VmgExit (Ghcb, SVM_EXIT_VMMCALL, 0, 0);
+ if (Status) {
+ DEBUG ((DEBUG_ERROR, "SVM_EXIT_VMMCALL failed %lx\n", Status));
You need to issue an SEV-ES guest termination vmexit followed by a deadloop to ensure
that boot does not proceed.

You probably also need to check for the RAX register for the return code.


+ }
+ VmgDone (Ghcb, InterruptState);
+ } else {
+ SetMemoryEncDecHypercall3AsmStub (
+ KVM_HC_MAP_GPA_RANGE,
+ PhysicalAddress,
+ Pages,
+ Mode
+ );
How do you know whether the hyperviosr supports the Live migration ? In other
words, is it safe to call the HC without knowing if HV supports the feature ?
I see that in patch#4 you are adding a support to query the HV features flag
to determine whether HV supports the Live migration. You probably need to
pull that function into this library and and check the feature flag before
invoking HC.

This library can also export the function for others to use. You can cache
the value on the first call (similar to how BaseMemEncryptSevLib does for
the MemEncryptSevIsEnabled).


Also, what will happen if we pass a bogus GPA. Does the HC return an error ?
Same as SEV-ES block, you probably need to check the RAX register for the
return code. On failure, cause an assert() and terminate the boot.


+ }
+}
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index f53efeae79..36f1d82ce7 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -176,6 +176,7 @@
VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLib.inf
+ MemEncryptHypercallLib|OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
!if $(SMM_REQUIRE) == FALSE
LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
!endif
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index b3662e17f2..2a743688b4 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -180,6 +180,7 @@
VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLib.inf
+ MemEncryptHypercallLib|OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
!if $(SMM_REQUIRE) == FALSE
LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
!endif
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 0a237a9058..eb9da51a15 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -180,6 +180,7 @@
VirtioLib|OvmfPkg/Library/VirtioLib/VirtioLib.inf
LoadLinuxLib|OvmfPkg/Library/LoadLinuxLib/LoadLinuxLib.inf
MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLib.inf
+ MemEncryptHypercallLib|OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
!if $(SMM_REQUIRE) == FALSE
LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
!endif
diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
index 3c1ca6bfd4..de0c052832 100644
--- a/OvmfPkg/OvmfXen.dsc
+++ b/OvmfPkg/OvmfXen.dsc
@@ -167,6 +167,7 @@
QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
MemEncryptSevLib|OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLib.inf
+ MemEncryptHypercallLib|OvmfPkg/Library/MemEncryptHypercallLib/MemEncryptHypercallLib.inf
LockBoxLib|OvmfPkg/Library/LockBoxLib/LockBoxBaseLib.inf
CustomizedDisplayLib|MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.inf
FrameBufferBltLib|MdeModulePkg/Library/FrameBufferBltLib/FrameBufferBltLib.inf
Update the AmdSev.dsc to include this library.


-Brijesh

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