On 07/14/17 22:30, Peter Jones wrote: > On Fri, Jul 14, 2017 at 08:04:14PM +0200, Laszlo Ersek wrote:
>> (2e) Modules that we should use. Again, in increasing order of >> dependence. And here I'll comment as well on what these do: >> >> Tcg2Config/Tcg2ConfigPei.inf -- Informs the firmware globally >> about the TPM device type. This >> module can perform device >> detection or read a cached value >> from a non-volatile UEFI >> variable. >> >> Tcg2Pei/Tcg2Pei.inf -- Initializes the TPM device and >> measures the firmware volumes in >> the PEI phase into the TPM's >> platform config registers. >> >> Tcg2Dxe/Tcg2Dxe.inf -- Measures DXE phase (and later) >> modules into the TPM's PCRs, and >> also lets the OS boot loader >> measure things, by exposing the >> EFI_TCG2_PROTOCOL. >> >> Tcg2Config/Tcg2ConfigDxe.inf -- Provides a Setup TUI interface to >> configure the TPM. IIUC, it can >> also save the configured TPM type >> for subsequent boots (see >> Tcg2ConfigPei.inf above). >> >> This driver stack supports the TIS (MMIO) hardware interface, which >> is advertized to the OS in the TPM2 ACPI Table's "start method" >> field with value 6. (The according macro is TPM2_START_METHOD_MMIO >> in the QEMU source code, and EFI_TPM2_ACPI_TABLE_START_METHOD_TIS >> in the edk2 source code.) >> >> Including these drivers should result in a functional >> EFI_TCG2_PROTOCOL, which is what OS boot loaders primarily care >> about, as I understand. >> >> Importantly, the driver stack above requires PEI-phase variable >> access, therefore >> <https://bugzilla.tianocore.org/show_bug.cgi?id=386> must be solved >> first. >> >> (I have had patches for said BZ ready for a while. I've failed to >> upstream them thus far because a pflash-based varstore is a hard >> requirement for them. I think that's a natural requirement, but >> thus far my arguments haven't proved compelling enough.) > > It does seem pretty natural... what's the counter argument? Jordan holds the opinion that "we should continue to support the memory vars, even if they have some obvious drawbacks": http://mid.mail-archive.com/149065122031.28789.9113394760317457361@jljusten-skl I'm of a different opinion: while I agree that we should not break the existing memory emulation, I'm also convinced that we should not develop new features for it, especially when a new feature (such as PEI-phase R/O variable access) simply cannot be *sensibly* extended to said emulation. Please see the first discussion under my original patch set: http://mid.mail-archive.com/148969026858.27582.5519307275216644796@jljusten-skl.jf.intel.com http://mid.mail-archive.com/319ff8f1-4e99-f977-5c2e-75509a222706@redhat.com http://mid.mail-archive.com/c20c6604-2153-aa57-cee5-24089a79b1e9@redhat.com http://mid.mail-archive.com/149034108785.2439.14733776608486243050@jljusten-skl http://mid.mail-archive.com/4b06b195-d8fb-a33e-3492-74fe396ebf6e@redhat.com And the second discussion under Jordan's counter-proposal: http://mid.mail-archive.com/a12bbf61-3f55-2fda-b855-58aeb99a4f42@redhat.com http://mid.mail-archive.com/149065122031.28789.9113394760317457361@jljusten-skl http://mid.mail-archive.com/121bb81b-08d1-d854-cf6f-ebc8268eb360@redhat.com http://mid.mail-archive.com/149076505135.12962.12298731900768295093@jljusten-skl Thanks Laszlo
