Apologies for the late reply, On Mon, 19 Feb 2024 at 09:34, Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote: > > Hi Ilias, > > On 2/18/24 11:03 PM, Ilias Apalodimas wrote: > > On Thu, 15 Feb 2024 at 05:02, Kuppuswamy Sathyanarayanan > > <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote: > >> To allow event log info access after boot, EFI boot stub extracts > >> the event log information and installs it in an EFI configuration > >> table. Currently, EFI boot stub only supports installation of event > >> log only for TPM 1.2 and TPM 2.0 protocols. Extend the same support > >> for CC protocol. Since CC platform also uses TCG2 format, reuse TPM2 > >> support code as much as possible. > >> > >> Link: https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#efi-cc-measurement-protocol [1] > >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > > [...] > > > >> +void efi_retrieve_eventlog(void) > >> +{ > >> + efi_physical_addr_t log_location = 0, log_last_entry = 0; > >> + efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID; > >> + efi_guid_t tpm2_guid = EFI_TCG2_PROTOCOL_GUID; > >> + int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2; > >> + efi_tcg2_protocol_t *tpm2 = NULL; > >> + efi_cc_protocol_t *cc = NULL; > >> + efi_bool_t truncated; > >> + efi_status_t status; > >> + > >> + status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2); > >> + if (status == EFI_SUCCESS) { > >> + status = efi_call_proto(tpm2, get_event_log, version, &log_location, > >> + &log_last_entry, &truncated); > >> + > >> + if (status != EFI_SUCCESS || !log_location) { > >> + version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2; > >> + status = efi_call_proto(tpm2, get_event_log, version, > >> + &log_location, &log_last_entry, > >> + &truncated); > >> + if (status != EFI_SUCCESS || !log_location) > >> + return; > >> + } > >> + > >> + efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry, > >> + truncated); > >> + return; > >> + } > >> + > >> + status = efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc); > >> + if (status == EFI_SUCCESS) { > >> + version = EFI_CC_EVENT_LOG_FORMAT_TCG_2; > >> + status = efi_call_proto(cc, get_event_log, version, &log_location, > >> + &log_last_entry, &truncated); > >> + if (status != EFI_SUCCESS || !log_location) > >> + return; > >> + > >> + efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry, > >> + truncated); > >> + return; > >> + } > >> +} > > [...] > > > > I haven't looked into CC measurements much, but do we always want to > > prioritize the tcg2 protocol? IOW if you have firmware that implements > > both, shouldn't we prefer the CC protocol for VMs? > > According the UEFI specification, sec "Conidential computing", if a firmware implements > the TPM, then it should be used and CC interfaces should not be published. So I think > we should check for TPM first, if it does not exist then try for CC. Ok thanks, that makes sense. That document also says the services should be implemented on a virtual firmware. I am unsure at the moment though if it's worth checking that and reporting an error otherwise. Thoughts? Thanks /Ilias > > https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#confidential-computing > > > Thanks > > /Ilias > > -- > Sathyanarayanan Kuppuswamy > Linux Kernel Developer >
