On 04/30/21 13:51, Brijesh Singh wrote: > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275 > > An SEV-SNP guest is required to perform the GHCB GPA registration. See > the GHCB specification for further details. > > Cc: James Bottomley <j...@linux.ibm.com> > Cc: Min Xu <min.m...@intel.com> > Cc: Jiewen Yao <jiewen....@intel.com> > Cc: Tom Lendacky <thomas.lenda...@amd.com> > Cc: Jordan Justen <jordan.l.jus...@intel.com> > Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org> > Cc: Laszlo Ersek <ler...@redhat.com> > Cc: Erdem Aktas <erdemak...@google.com> > Signed-off-by: Brijesh Singh <brijesh.si...@amd.com> > --- > MdePkg/Include/Register/Amd/Fam17Msr.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/MdePkg/Include/Register/Amd/Fam17Msr.h > b/MdePkg/Include/Register/Amd/Fam17Msr.h > index a65d51ab12..e19bd04b6c 100644 > --- a/MdePkg/Include/Register/Amd/Fam17Msr.h > +++ b/MdePkg/Include/Register/Amd/Fam17Msr.h > @@ -53,6 +53,11 @@ typedef union { > UINT64 Features:52; > } GhcbHypervisorFeatures; > > + struct { > + UINT64 Function:12; > + UINT64 GuestFrameNumber:52; > + } GhcbGpaRegister; > + > VOID *Ghcb; > > UINT64 GhcbPhysicalAddress; > @@ -62,6 +67,8 @@ typedef union { > #define GHCB_INFO_SEV_INFO_GET 2 > #define GHCB_INFO_CPUID_REQUEST 4 > #define GHCB_INFO_CPUID_RESPONSE 5 > +#define GHCB_INFO_GHCB_GPA_REGISTER_REQUEST 18 > +#define GHCB_INFO_GHCB_GPA_REGISTER_RESPONSE 19 > #define GHCB_HYPERVISOR_FEATURES_REQUEST 128 > #define GHCB_HYPERVISOR_FEATURES_RESPONSE 129 > #define GHCB_INFO_TERMINATE_REQUEST 256 >
The number match the spec (2.0), but I have some remarks / questions. (1) Patch #2 (SVM_EXIT_HYPERVISOR_FEATURES) and this patch (GHCB_INFO_GHCB_GPA_REGISTER_REQUEST) break the nice alignments of the macro values (replacement texts) in both header files. Can you prepend a whitespace-only patch that simply moves the affected "columns" to the right far enough? (2) I've checked section 2.3.2 "GHCB GPA Registration" in the spec (2.0). What is the specific risk of allowing a guest to switch from one GHCB address to another? (3) It seems strange to expect that a guest stick with a particular GHCB address for its entire lifetime (including firmware and OS) -- in fact OVMF already uses multiple GHCB addresses. The spec does not explain how the guest can "unlock" (de-register) a registered GHCB address. Furthermore, if a guest can do that *at all* (which I think it must -- we're already using different GHCB addresses between SEC and DXE, for example), then what protection does the *temporary* locking of the GHCB address provide? I'll stop reviewing here, because I think I need to understand your answers. I'd like to have a rudimentary mental basis for reviewing the rest. Thanks Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#74696): https://edk2.groups.io/g/devel/message/74696 Mute This Topic: https://groups.io/mt/82479050/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
