[RFC] efi/tpm: add efi.tpm_log as a reserved region in 820_table_firmware

[Ard Biesheuvel]

(cc Dave)

Full thread here:
https://lore.kernel.org/all/CAMj1kXG1hbiafKRyC5qM1Vj5X7x-dmLndqqo2AYnHMRxDz-80w@mail.gmail.com/T/#u

On Thu, 12 Sept 2024 at 16:05, Ard Biesheuvel <ardb at kernel.org> wrote:
>
> On Thu, 12 Sept 2024 at 15:55, Usama Arif <usamaarif642 at gmail.com> wrote:
> >
> >
> >
> > On 12/09/2024 14:10, Ard Biesheuvel wrote:
> > > Does the below help at all?
> > >
> > > --- a/drivers/firmware/efi/tpm.c
> > > +++ b/drivers/firmware/efi/tpm.c
> > > @@ -60,7 +60,7 @@ int __init efi_tpm_eventlog_init(void)
> > >         }
> > >
> > >         tbl_size = sizeof(*log_tbl) + log_tbl->size;
> > > -       memblock_reserve(efi.tpm_log, tbl_size);
> > > +       efi_mem_reserve(efi.tpm_log, tbl_size);
> > >
> > >         if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) {
> > >                 pr_info("TPM Final Events table not present\n");
> >
> > Unfortunately not. efi_mem_reserve updates e820_table, while kexec looks at /sys/firmware/memmap
> > which is e820_table_firmware.
> >
> > arch_update_firmware_area introduced in the RFC patch does the same thing as efi_mem_reserve does at
> > its end, just with e820_table_firmware instead of e820_table.
> > i.e. efi_mem_reserve does:
> >         e820__range_update(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED);
> >         e820__update_table(e820_table);
> >
> > while arch_update_firmware_area does:
> >         e820__range_update_firmware(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED);
> >         e820__update_table(e820_table_firmware);
> >
>
> Shame.
>
> Using efi_mem_reserve() is appropriate here in any case, but I guess
> kexec on x86 needs to be fixed to juggle the EFI memory map, memblock
> table, and 3 (!) versions of the E820 table in the correct way
> (e820_table, e820_table_kexec and e820_table_firmware)
>
> Perhaps we can put this additional logic in x86's implementation of
> efi_arch_mem_reserve()? AFAICT, all callers of efi_mem_reserve() deal
> with configuration tables produced by the firmware that may not be
> reserved correctly if kexec looks at e820_table_firmware[] only.