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

[Usama Arif]

On 13/09/2024 12:49, Dave Young wrote:
> On Fri, 13 Sept 2024 at 19:13, Dave Young <dyoung@xxxxxxxxxx> wrote:
>>
>> 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.
> 
> Hold on,  I'm not sure about above :(
> 
> checking the efi_arch_mem_reserve(), currently it updates the e820
> table, if you update the e820_table_kexec and e820_table_firmware then
> I think both kexec_load and kexec_file_load will work.
> 
> Anyway I was not aware very much about the firmware e820 tables and
> kexec tables when they were created.   I suspect that a cleanup and
> revisit is needed.  I will have a look at that.

Yes, I feel like there is one too many tables! From reading the code
I understand that /sys/firmware/memmap should contain the untouched map
at time of boot, i.e. e820_table_firmware. But I would be in favour of
getting rid of e820_table_firmware, and just having e820_table_kexec.
And /sys/firmware/memmap gets data from e820_table_kexec.
> 
> For Ard's fix to allocate it as ACPI memory, I think it should be good
> and simpler.
>

 
Agreed!

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