linux-kernel - Re: kexec regression since 4.9 caused by efi

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Message-ID: <20170316175048.GA25230@vader.DHCP.thefacebook.com>
Date:   Thu, 16 Mar 2017 10:50:48 -0700
From:   Omar Sandoval <osandov@...ndov.com>
To:     Matt Fleming <matt@...eblueprint.co.uk>
Cc:     Dave Young <dyoung@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        kexec@...ts.infradead.org, linux-efi@...r.kernel.org
Subject: Re: kexec regression since 4.9 caused by efi

On Thu, Mar 16, 2017 at 12:41:32PM +0000, Matt Fleming wrote:
> On Mon, 13 Mar, at 03:37:48PM, Dave Young wrote:
> > 
> > Omar, could you try below patch? Looking at the efi_mem_desc_lookup, it is not
> > correct to be used in efi_arch_mem_reserve, if it passed your test, I
> > can rewrite patch log with more background and send it out:
> > 
> >         for_each_efi_memory_desc(md) {
> > 		[snip]
> >                 if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
> >                     md->type != EFI_BOOT_SERVICES_DATA &&
> >                     md->type != EFI_RUNTIME_SERVICES_DATA) {
> >                         continue;
> >                 }
> > 
> > In above code, it meant to get a md of EFI_MEMORY_RUNTIME of either boot
> > data or runtime data, this is wrong for efi_mem_reserve, because we are
> > reserving boot data which has no EFI_MEMORY_RUNTIME attribute at the
> > running time. Just is happened to work and we did not capture the error.
> 
> Wouldn't something like this be simpler?
> 
> ---
> 
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index 30031d5293c4..cdfe8c628959 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -201,6 +201,10 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
>  		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);

This works for me.

Reported-and-tested-by: Omar Sandoval <osandov@...com>