Re: [PATCH v2] x86/boot: Use EFI setup data if provided

Chao Fan
2019-03-28T06:27:44Z

On Thu, Mar 28, 2019 at 04:17:16AM +0000, Junichi Nomura wrote:
>On 2019/03/27 10:48, bhe@redhat.com wrote:
>>>> So efi_get_rsdp_addr() needs to be refactored in such a way so that at
>>>> least the loop towards the end gets carved out into a separate function
>>>> - __efi_get_rsdp_addr() or so - which gets config_tables, nr_tables and
>>>> size as arguments and finds the RSDP address in the kexec-ed kernel.
>>>
>>> You need to carve out the loop at the end and make it into a separate
>>> __efi_get_rsdp_addr() function which gets the physical or the virtual
>>> address.
>>
>> I guess Boris is suggesting code like below. Please correct me if I am
>> wrong.
>>
>> static acpi_physical_address _efi_get_rsdp_addr(efi_config_table tbl, ...)
>> {
>> /* Get EFI tables from systab. */
>> for (i = 0; i < nr_tables; i++) {
>> ...
>> }
>> return rsdp_addr;
>> }
>>
>> static acpi_physical_address efi_get_rsdp_addr(void)
>> {
>> ...
>> /* Get systab from boot params. */
>> ...
>> /* Handle EFI bitness properly */
>> ...
>> return _efi_get_rsdp_addr();
>> }
>>
>>
>> static acpi_physical_address kexec_get_rsdp_addr(void)
>> {
>> if (!is_kexec_booted)
>> return 0;
>>
>> efi_get_setup_data_addr();
>> ...
>> /* Handle EFI bitness properly */
>> ...
>> return _efi_get_rsdp_addr();
>> }
>
>I still don't get it... We still need systab for kexec case as well
>to get nr_tables. Don't we?
>
>> acpi_physical_address get_rsdp_addr(void)
>> {
>> acpi_physical_address pa;
>>
>> pa = get_acpi_rsdp();
>>
>> if (!pa)
>> pa = boot_params->acpi_rsdp_addr;
>>
>>
>> /**
>> /*I think here we should check if it's kexec booted firstly.
>> * Skip it if not kexec. this can avoid the wrong kexec virt
>> * addr parsing./
>> if (!pa)
>> pa = kexec_get_rdsp_addr(); <--- new function
>>
>> if (!pa)
>> pa = efi_get_rsdp_addr();
>>
>
>Shouldn't t efi_get_rsdp_addr() check "is_kexec_booted" and exit
>early so that it never tries to use virtual config_tables pointer
>if for some unknown resason kexec_get_rsdp_addr() failed.

In my understanding, in EFI issue, RSDP is from efi_get_rsdp_addr() or
kexec_get_rdsp_addr()(only in kexec environment). So in these two functions
only one can be excuted, so how about this:

if (is_kexec_booted)
pa = kexec_get_rdsp_addr(); <--- new function
else
pa = efi_get_rsdp_addr();

And also split the same code as _efi_get_rsdp_addr().
If there is something wrong in my understanding, please let me know.

Thanks,
Chao Fan

>
>Currently I check "is_kexec_booted" by subset of efi_get_setup_data_addr().
>Do you know a simpler way to check "is_kexec_booted"?
>
>> if (!pa)
>> pa = bios_get_rsdp_addr();
>>
>> return pa;
>> }
>
>--
>Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.
>