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OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Clear C-bit when SEV is active

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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>
This commit is contained in:
Brijesh Singh
2018-03-09 10:06:03 -06:00
committed by Laszlo Ersek
parent d5a002aba0
commit e4a1d5a7c4
5 changed files with 84 additions and 0 deletions
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2
OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesSmm.inf
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@@ -40,6 +40,7 @@
FwBlockService.c
FwBlockServiceSmm.c
QemuFlash.c
QemuFlashSmm.c
[Packages]
MdePkg/MdePkg.dec
@@ -53,6 +54,7 @@
DevicePathLib
DxeServicesTableLib
MemoryAllocationLib
MemEncryptSevLib
PcdLib
SmmServicesTableLib
UefiBootServicesTableLib