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

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Message-ID: <20170316121532.GE6261@codeblueprint.co.uk>
Date:   Thu, 16 Mar 2017 12:15:32 +0000
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Omar Sandoval <osandov@...ndov.com>,
        Dave Young <dyoung@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel-team@...com,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>
Subject: Re: kexec regression since 4.9 caused by efi

On Thu, 09 Mar, at 12:53:36PM, Ard Biesheuvel wrote:
> 
> Hi Omar,
> 
> Thanks for tracking this down.
> 
> I wonder if this is an unintended side effect of the way we repurpose
> the EFI_MEMORY_RUNTIME attribute in efi_arch_mem_reserve(). AFAIUI,
> splitting memory map entries should only be necessary for regions that
> are not runtime memory regions to begin with, and so whether their
> virtual mapping address makes sense or not should be irrelevant.
> 
> Perhaps this only illustrates my lack of understanding of the x86 way
> of doing this, so perhaps Matt can shed some light on this?

Sorry for the delay.

Yes, Ard is correct. It's not necessary to split/reserve memory
regions that already have the EFI_MEMORY_RUNTIME attribute.