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

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Date:   Wed, 4 Dec 2019 15:59:17 +0800
From:   Dave Young <dyoung@...hat.com>
To:     linux-efi@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Michael Weiser <michael@...ser.dinsnail.net>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        kexec@...ts.infradead.org, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/efi: update e820 about reserved EFI boot services
 data to fix kexec breakage

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@...hat.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