BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
The flash detection routine will attempt to determine how the flash
device behaves (e.g. ROM, RAM, Flash). But when SEV-ES is enabled and
the flash device behaves as a ROM device (meaning it is marked read-only
by the hypervisor), this check may result in an infinite nested page fault
because of the attempted write. Since the instruction cannot be emulated
when SEV-ES is enabled, the RIP is never advanced, resulting in repeated
nested page faults.
When SEV-ES is enabled, exit the flash detection early and assume that
the FD behaves as Flash. This will result in QemuFlashWrite() being called
to store EFI variables, which will also result in an infinite nested page
fault when the write is performed. In this case, update QemuFlashWrite()
to use the VMGEXIT MMIO write support to have the hypervisor perform the
write without having to emulate the instruction.
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
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>
In preparation for introducing an SMM interface to this driver, move the
following traits to separate files, so that we can replace them in the new
SMM INF file:
- Protocol installations. The SMM driver will install protocol interfaces
in the SMM protocol database, using SMM services.
- Virtual address change handler and pointer conversions. SMM drivers run
with physical mappings and pointers must not be converted.
There are further restrictions and changes for an SMM driver, but the rest
of the code either complies with those already, or will handle the changes
transparently. For example:
- SMM drivers have access to both UEFI and SMM protocols in their entry
points (see the PI spec 1.4, "1.7 SMM Driver Initialization"),
- MemoryAllocationLib has an SMM instance that serves allocation requests
with the gSmst->SmmAllocatePool() service transparently, allocating
runtime-marked SMRAM.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18671 6f19259b-4bc3-4df7-8a09-765794883524
Tom Lendacky
Michael D Kinney
Brijesh Singh
Laszlo Ersek