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OvmfPkg/BaseMemEncryptSevLib: Re-organize page state change support

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BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654

In preparation for running under an SVSM at VMPL1 or higher (higher
numerically, lower privilege), re-organize the way a page state change
is performed in order to free up the GHCB for use by the SVSM support.

Currently, the page state change logic directly uses the GHCB shared
buffer to build the page state change structures. However, this will be
in conflict with the use of the GHCB should an SVSM call be required.

Instead, use a separate buffer (an area in the workarea during SEC and
an allocated page during PEI/DXE) to hold the page state change request
and only update the GHCB shared buffer as needed.

Since the information is copied to, and operated on, in the GHCB shared
buffer this has the added benefit of not requiring to save the start and
end entries for use when validating the memory during the page state
change sequence.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Min Xu <min.m.xu@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Tom Lendacky
2024-03-08 07:31:11 -08:00
committed by mergify[bot]
parent f40c1f2a30
commit 2b330b57db
7 changed files with 146 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiDxeVirtualMemory.c
View File

@@ -3,7 +3,7 @@
Virtual Memory Management Services to set or clear the memory encryption bit
Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2017 - 2020, AMD Incorporated. All rights reserved.<BR>
Copyright (c) 2017 - 2024, AMD Incorporated. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
@@ -23,6 +23,8 @@ STATIC BOOLEAN mAddressEncMaskChecked = FALSE;
STATIC UINT64 mAddressEncMask;
STATIC PAGE_TABLE_POOL *mPageTablePool = NULL;
STATIC VOID *mPscBuffer = NULL;
typedef enum {
SetCBit,
ClearCBit
@@ -786,7 +788,19 @@ SetMemoryEncDec (
// The InternalSetPageState() is used for setting the page state in the RMP table.
//
if (!Mmio && (Mode == ClearCBit) && MemEncryptSevSnpIsEnabled ()) {
InternalSetPageState (PhysicalAddress, EFI_SIZE_TO_PAGES (Length), SevSnpPageShared, FALSE);
if (mPscBuffer == NULL) {
mPscBuffer = AllocateReservedPages (1);
ASSERT (mPscBuffer != NULL);
}
InternalSetPageState (
PhysicalAddress,
EFI_SIZE_TO_PAGES (Length),
SevSnpPageShared,
FALSE,
mPscBuffer,
EFI_PAGE_SIZE
);
}
//
@@ -975,11 +989,18 @@ SetMemoryEncDec (
// The InternalSetPageState() is used for setting the page state in the RMP table.
//
if ((Mode == SetCBit) && MemEncryptSevSnpIsEnabled ()) {
if (mPscBuffer == NULL) {
mPscBuffer = AllocateReservedPages (1);
ASSERT (mPscBuffer != NULL);
}
InternalSetPageState (
OrigPhysicalAddress,
EFI_SIZE_TO_PAGES (OrigLength),
SevSnpPagePrivate,
FALSE
FALSE,
mPscBuffer,
EFI_PAGE_SIZE
);
}