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

[Dave Young]

On Sat, 14 Sept 2024 at 17:24, Dave Young <dyoung@xxxxxxxxxx> wrote:
>
> On Sat, 14 Sept 2024 at 16:31, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> >
> > On Sat, 14 Sept 2024 at 08:46, Dave Young <dyoung@xxxxxxxxxx> wrote:
> > >
> > > On Fri, 13 Sept 2024 at 18:56, Dave Young <dyoung@xxxxxxxxxx> 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.
>
> Updating e820_table should be good enough, it depends on where the
> corruption is happening.
>
> kexec will find a suitable memory for the kernel via searching through
> the system ram resources.   So efi_mem_reserve will update e820_table,
> then reserve in the resources list as E820_TYPE_RESERVED, thus it
> should not be a problem.
> During the 2nd kernel boot phase, it is carried as EFI_LOADER_DATA
> with EFI_MEMORY_RUNTIME attribute, I think it is also fine,  and later
> efi_mem_reserve will be called as what have been done in previous
> kernel.
>
> So I think no need to update the e820_table_kexec and e820_table_firmware


Hmm,  oops, I again forgot the kexec_load code in userspace kexec-tools.
The kexec-tools code still searching for memory ranges from 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.
> > > >
> > >
> > > I'm still confused after reading the code about why this issue can
> > > still happen with a efi_mem_reserve.
> > > Usama, Breno, could any of you share the exact steps on how to
> > > reproduce this issue with a kvm guest?
> > >
> >
> > The code does not use efi_mem_reserve() only memblock_reserve().
>
> Yes, I see this, I just thought that Usama tested with changes to
> efi_mem_reserve and it still did not work, this is what I'm confused
> about.
>
> But maybe Usama did not test and only checked the code and assumed
> that we have to update the e820_table_kexec and e820_table_firmware.
> See my reply inline above.

Please ignore the above comment.   The userspace code does need the
e820_table_firmware.
So the best way to make it easier is to clean up the e820 tables and
maintain only one table then the kernel kexec_file_load behavior will
be the same as the userspace.   But need a closer look about the
details, eg. if the hibernate (mentioned in code comment) is happy.

Or to change userspace to go through the /proc/iomem instead of
checking the /sys/firmware/memmap

>
> Thanks
> Dave
> >