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

[Dave Young]

On Fri, 13 Sept 2024 at 19:07, Usama Arif <usamaarif642@xxxxxxxxx> wrote:
>
>
>
> On 13/09/2024 11:56, Dave Young wrote:
> > On Thu, 12 Sept 2024 at 22:15, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> >>
> >> (cc Dave)
> >
> > Thanks for ccing me.
> >
> >>
> >> Full thread here:
> >> https://lore.kernel.org/all/CAMj1kXG1hbiafKRyC5qM1Vj5X7x-dmLndqqo2AYnHMRxDz-80w@xxxxxxxxxxxxxx/T/#u
> >>
> >> On Thu, 12 Sept 2024 at 16:05, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> >>>
> >>> On Thu, 12 Sept 2024 at 15:55, Usama Arif <usamaarif642@xxxxxxxxx> 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.
> >>
> >
> > I have not read all the conversations,  let me have a look and response later.
> >
> > The first glance about the patch is that I think the kexec_file_load
> > syscall (default of latest kexec-tools) will not use
> > e820_table_firmware AFAIK.  it will only use e820_table_kexec.
>
> I initially thought that as well. But it looks like kexec just reads /sys/firmware/memmap
>
> https://github.com/horms/kexec-tools/blob/main/kexec/firmware_memmap.h#L29
>
> which is e820_table_firmware.

That piece of code is only used by kexec_load

>
> The patch that Ard sent in https://lore.kernel.org/all/20240912155159.1951792-2-ardb+git@xxxxxxxxxx/
> is the right approach to it I believe, and I dont see the issue anymore after applying that patch.
>
> >
> > Usama, can you confirm how you tested this?
> > kexec -c -l  will use kexec_load syscall
>
> I am currently testing in my VM setup with kexec_load. But production is running
> kexec_file_load and has the same issue.

Ok, I mean efi_mem_reserve should be able to work if you retest with
kexec_file_load.

>
> Thanks,
> Usama
>
> > kexec [-s] -l will use kexec_file_load syscall
> >
> > Thanks
> > Dave
> >
>