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* OvfmPkg/VmgExitLib: Validate #VC MMIO is to un-encrypted memoryTom Lendacky2021-01-071-0/+2
| | | | | | | | | | | | | | | | | | | | | | | 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>
* OvmfPkg/VmgExitLib: Support nested #VCsTom Lendacky2021-01-071-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* OvmfPkg/VmgExitLib: Implement library support for VmgExitLib in OVMFTom Lendacky2020-08-171-0/+36
The base VmgExitLib library provides a default limited interface. As it does not provide full support, create an OVMF version of this library to begin the process of providing full support of SEV-ES within OVMF. SEV-ES support is only provided for X64 builds, so only OvmfPkgX64.dsc is updated to make use of the OvmfPkg version of the library. Cc: Jordan Justen <jordan.l.justen@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com> Acked-by: Laszlo Ersek <lersek@redhat.com> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Regression-tested-by: Laszlo Ersek <lersek@redhat.com>