e4a1d5a7c4
Commit:24e4ad7 (OvmfPkg: Add AmdSevDxe driver) added a driver which runs early in DXE phase and clears the C-bit from NonExistent entry -- which is later split and accommodate the flash MMIO. When SMM is enabled, we build two sets of page tables; first page table is used when executing code in non SMM mode (SMM-less-pgtable) and second page table is used when we are executing code in SMM mode (SMM-pgtable). During boot time, AmdSevDxe driver clears the C-bit from the SMM-less-pgtable. But when SMM is enabled, Qemu Flash services are used from SMM mode. In this patch we explicitly clear the C-bit from Qemu flash MMIO range before we probe the flash. When OVMF is built with SMM_REQUIRE then call to initialize the flash services happen after the SMM-pgtable is created and processor has served the first SMI. At this time we will have access to the SMM-pgtable. Cc: Jordan Justen <jordan.l.justen@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> [lersek@redhat.com: trivial coding style improvements] Reviewed-by: Laszlo Ersek <lersek@redhat.com>
55 lines
1.7 KiB
C
55 lines
1.7 KiB
C
/** @file
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Define the module hooks used while probing the QEMU flash device.
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Copyright (C) 2018, Advanced Micro Devices. All rights reserved.
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This program and the accompanying materials are licensed and made available
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under the terms and conditions of the BSD License which accompanies this
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distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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**/
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#include <Library/BaseMemoryLib.h>
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#include <Library/DebugLib.h>
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#include <Library/PcdLib.h>
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#include <Library/MemEncryptSevLib.h>
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#include "QemuFlash.h"
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VOID
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QemuFlashBeforeProbe (
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IN EFI_PHYSICAL_ADDRESS BaseAddress,
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IN UINTN FdBlockSize,
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IN UINTN FdBlockCount
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)
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{
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EFI_STATUS Status;
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ASSERT (FeaturePcdGet (PcdSmmSmramRequire));
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if (!MemEncryptSevIsEnabled ()) {
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return;
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}
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//
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// When SEV is enabled, AmdSevDxe runs early in DXE phase and clears the
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// C-bit from the NonExistent entry -- which is later split and accommodate
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// the flash MMIO but the driver runs in non SMM context hence it cleared the
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// flash ranges from non SMM page table. When SMM is enabled, the flash
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// services are accessed from the SMM mode hence we explicitly clear the
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// C-bit on flash ranges from SMM page table.
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//
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Status = MemEncryptSevClearPageEncMask (
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0,
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BaseAddress,
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EFI_SIZE_TO_PAGES (FdBlockSize * FdBlockCount),
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FALSE
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);
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ASSERT_EFI_ERROR (Status);
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}
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