In the next two patches, we'll temporarily decrypt the pages containing
the initial SMRAM save state map, for SMBASE relocation. (Unlike the
separate, relocated SMRAM save state map of each VCPU, the original,
shared map behaves similarly to a "common buffer" between guest and host.)
The decryption will occur near the beginning of the DXE phase, in
AmdSevDxe, and the re-encryption will occur in PiSmmCpuDxeSmm, via OVMF's
SmmCpuFeaturesLib instance.
There is a non-trivial time gap between these two points, and the DXE
phase might use the pages overlapping the initial SMRAM save state map for
arbitrary purposes meanwhile. In order to prevent any information leak
towards the hypervisor, make sure the DXE phase puts nothing in those
pages until re-encryption is done.
Creating a memalloc HOB for the area in question is safe:
- the temporary SEC/PEI RAM (stack and heap) is based at
PcdOvmfSecPeiTempRamBase, which is above 8MB,
- the permanent PEI RAM (installed in PlatformPei's PublishPeiMemory()
function) never starts below PcdOvmfDxeMemFvBase, which is also above
8MB.
The allocated pages can be released to the DXE phase after SMBASE
relocation and re-encryption are complete.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
"Platform.h" declares the AmdSevInitialize() function without EFIAPI, but
the definition in "AmdSev.c" includes EFIAPI.
GCC toolchains without LTO do not catch this error because "AmdSev.c" does
not include "Platform.h"; i.e. the declaration used by callers such as
"Platform.c" is not actually matched against the function definition at
build time.
With LTO enabled, the mismatch is found -- however, as a warning only, due
to commit f8d0b96629 ("BaseTools GCC5: disable warnings-as-errors for
now", 2016-08-03).
Include the header in the C file (which turns the issue into a hard build
error on all GCC toolchains), plus sync the declaration from the header
file to the C file.
There's been no functional breakage because AmdSevInitialize() takes no
parameters.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Fixes: 13b5d743c8
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
The following commit:
1fea9ddb4e OvmfPkg: execute option ROM images regardless of Secure Boot
sets the OptionRomImageVerificationPolicy to ALWAYS_EXECUTE the expansion
ROMs attached to the emulated PCI devices. A expansion ROM constitute
another channel through which a cloud provider (i.e hypervisor) can
inject a code in guest boot flow to compromise it.
When SEV is enabled, the bios code has been verified by the guest owner
via the SEV guest launch sequence before its executed. When secure boot,
is enabled, lets make sure that we do not allow guest bios to execute a
code which is not signed by the guest owner.
Fixes: https://bugzilla.tianocore.org/show_bug.cgi?id=728
Cc: Chao Zhang <chao.b.zhang@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Secure Encrypted Virtualization (SEV) guest VMs have the concept of
private and shared memory. Private memory is encrypted with the
guest-specific key, while shared memory may be encrypted with hypervisor
key. Certain types of memory (namely instruction pages and guest page
tables) are always treated as private memory by the hardware.
For data memory, SEV guest VMs can choose which pages they would like
to be private. The choice is done using the standard CPU page tables
using the C-bit. When building the initial page table we mark all the
memory as private.
The patch sets the memory encryption PCD. The PCD is consumed by the
following edk2 modules, which manipulate page tables:
- PEI phase modules: CapsulePei, DxeIplPeim, S3Resume2Pei.
CapsulePei is not used by OVMF. DxeIplPeim consumes the PCD at the
end of the PEI phase, when it builds the initial page tables for the
DXE core / DXE phase. S3Resume2Pei does not consume the PCD in its
entry point function, only when DxeIplPeim branches to the S3 resume
path at the end of the PEI phase, and calls S3Resume2Pei's
EFI_PEI_S3_RESUME2_PPI.S3RestoreConfig2() member function.
Therefore it is safe to set the PCD for these modules in PlatformPei.
- DXE phase modules: BootScriptExecutorDxe, CpuDxe, PiSmmCpuDxeSmm.
They are all dispatched after the PEI phase, so setting the PCD for
them in PlatformPei is safe. (BootScriptExecutorDxe is launched "for
real" in the PEI phase during S3 resume, but it caches the PCD into a
static variable when its entry point is originally invoked in DXE.)
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Laszlo Ersek
Brijesh Singh