linux-kernel - Re: [PATCH v2] x86/efi: Correct ident mapping of efi old

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Date:   Mon, 8 May 2017 09:36:49 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Bhupesh Sharma <bhsharma@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Matt Fleming <matt@...eblueprint.co.uk>
Cc:     linux-kernel@...r.kernel.org, Dave Young <dyoung@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Garnier <thgarnie@...gle.com>,
        Kees Cook <keescook@...omium.org>, x86@...nel.org,
        linux-efi@...r.kernel.org, Alex Thorlton <athorlton@....com>,
        Russ Anderson <rja@....com>,
        Dimitri Sivanich <sivanich@....com>,
        Mike Travis <travis@....com>
Subject: Re: [PATCH v2] x86/efi: Correct ident mapping of efi old_map when
 kalsr enabled

Thanks for explaining, Bhupesh. 

BIOS issue of SGI uv1 is still not fixed. There's a quirk for uv1 to
use efi old map:

void __init efi_apply_memmap_quirks(void)
{
	...
	...
        /* UV2+ BIOS has a fix for this issue.  UV1 still needs the quirk. */
        if (dmi_check_system(sgi_uv1_dmi))
                set_bit(EFI_OLD_MEMMAP, &efi.flags);
}

And because of some reasons, redhat also need efi old_map now.

Hi Matt,

This v2 patch works on my kvm guest, however there's still problem on
SGI system. I will post v3 later after it's handled. So nack this v2
patch.

Thanks
Baoquan

On 05/08/17 at 12:07am, Bhupesh Sharma wrote:
> On Sat, May 6, 2017 at 5:06 AM, Borislav Petkov <bp@...en8.de> wrote:
> > On Fri, May 05, 2017 at 09:42:14PM +0100, Matt Fleming wrote:
> >> (Including the folks from SGI since this was hit on a UV system)
> >
> > Wasn't there a BIOS fix supplied at some point which obviated the need
> > to boot with efi=old_map on SGI boxes?
> >
> 
> AFAICR, the bios fixes were provided only for SGI boxes with BIOS
> version greater than or equal to UV2 (so upstream with recent bios
> works on UV2, UV3, and UV4 hardware platforms, both with old and new
> mapping, with new mapping being the default), however the UV1
> platforms still use efi=old_map
> 
> Also as mentioned above since commit
> caef78b6cdeddf4ad364f95910bba6b43b8eb9bf fixed the efi=old_map support
> on UV systems even with new bios, they should ideally all boot up
> properly in upstream both with 'nokaslr' and without 'nokaslr' in the
> bootargs when efi=old_map is used.
> 
> Regards,
> Bhupesh