BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108
When SEV-ES is active, and MMIO operation will trigger a #VC and the
VmgExitLib exception handler will process this MMIO operation.
A malicious hypervisor could try to extract information from encrypted
memory by setting a reserved bit in the guests nested page tables for
a non-MMIO area. This can result in the encrypted data being copied into
the GHCB shared buffer area and accessed by the hypervisor.
Prevent this by ensuring that the MMIO source/destination is un-encrypted
memory. For the APIC register space, access is allowed in general.
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <0cf28470ad5e694af45f7f0b35296628f819567d.1610045305.git.thomas.lendacky@amd.com>
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108
In order to be able to issue messages or make interface calls that cause
another #VC (e.g. GetLocalApicBaseAddress () issues RDMSR), add support
for nested #VCs.
In order to support nested #VCs, GHCB backup pages are required. If a #VC
is received while currently processing a #VC, a backup of the current GHCB
content is made. This allows the #VC handler to continue processing the
new #VC. Upon completion of the new #VC, the GHCB is restored from the
backup page. The #VC recursion level is tracked in the per-vCPU variable
area.
Support is added to handle up to one nested #VC (or two #VCs total). If
a second nested #VC is encountered, an ASSERT will be issued and the vCPU
will enter CpuDeadLoop ().
For SEC, the GHCB backup pages are reserved in the OvmfPkgX64.fdf memory
layout, with two new fixed PCDs to provide the address and size of the
backup area.
For PEI/DXE, the GHCB backup pages are allocated as boot services pages
using the memory allocation library.
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <ac2e8203fc41a351b43f60d68bdad6b57c4fb106.1610045305.git.thomas.lendacky@amd.com>
Tom Lendacky