Re: [PATCH] x86/efi: update e820 about reserved EFI boot services data to fix kexec breakage

Dave Young
2019-12-04T07:59:34Z

On 12/04/19 at 03:52pm, Dave Young wrote:
> Michael Weiser reported he got below error during a kexec rebooting:
> esrt: Unsupported ESRT version 2904149718861218184.
>
> The ESRT memory stays in EFI boot services data, and it was reserved
> in kernel via efi_mem_reserve(). The initial purpose of the reservation
> is to reuse the EFI boot services data across kexec reboot. For example
> the BGRT image data and some ESRT memory like Michael reported.
>
> But although the memory is reserved it is not updated in X86 e820 table.
> And kexec_file_load iterate system ram in io resource list to find places
> for kernel, initramfs and other stuff. In Michael's case the kexec loaded
> initramfs overwritten the ESRT memory and then the failure happened.

s/overwritten/overwrote :) If need a repost please let me know..

>
> Since kexec_file_load depends on the e820 to be updated, just fix this
> by updating the reserved EFI boot services memory as reserved type in e820.
>
> Originally any memory descriptors with EFI_MEMORY_RUNTIME attribute are
> bypassed in the reservation code path because they are assumed as reserved.
> But the reservation is still needed for multiple kexec reboot.
> And it is the only possible case we come here thus just drop the code
> chunk then everything works without side effects.
>
> On my machine the ESRT memory sits in an EFI runtime data range, it does
> not trigger the problem, but I successfully tested with BGRT instead.
> both kexec_load and kexec_file_load work and kdump works as well.
>
> Signed-off-by: Dave Young <dyoung@redhat.com>
> ---
> arch/x86/platform/efi/quirks.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> --- linux-x86.orig/arch/x86/platform/efi/quirks.c
> +++ linux-x86/arch/x86/platform/efi/quirks.c
> @@ -260,10 +260,6 @@ void __init efi_arch_mem_reserve(phys_ad
> return;
> }
>
> - /* No need to reserve regions that will never be freed. */
> - if (md.attribute & EFI_MEMORY_RUNTIME)
> - return;
> -
> size += addr % EFI_PAGE_SIZE;
> size = round_up(size, EFI_PAGE_SIZE);
> addr = round_down(addr, EFI_PAGE_SIZE);
> @@ -293,6 +289,8 @@ void __init efi_arch_mem_reserve(phys_ad
> early_memunmap(new, new_size);
>
> efi_memmap_install(new_phys, num_entries);
> + e820__range_update(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED);
> + e820__update_table(e820_table);
> }
>
> /*

Michael, could you a one more test and provide a tested-by if it works
for you?

Thanks
Dave