linux-kernel - Re: [PATCH -v2] EFI: Runtime services virtual mapping

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Message-ID: <20130923062947.GA2527@pd.tnic>
Date:	Mon, 23 Sep 2013 08:29:47 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Dave Young <dyoung@...hat.com>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...e.de>,
	Matt Fleming <matt@...sole-pimps.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Vivek Goyal <vgoyal@...hat.com>, linux-efi@...r.kernel.org
Subject: Re: [PATCH -v2] EFI: Runtime services virtual mapping

On Mon, Sep 23, 2013 at 01:47:41PM +0800, Dave Young wrote:
> > +	unsigned long size = md->num_pages << PAGE_SHIFT;
> > +
> > +	efi_va -= size;
> > +	if (efi_va < EFI_VA_END) {
> > +		pr_warning(FW_WARN "VA address range overflow!\n");
> > +		return;
> > +	}
> > +
> > +	/* Do the 1:1 map */
> > +	__map_region(md, md->phys_addr);
> > +
> > +	/* Do the VA map */
> > +	__map_region(md, efi_va);
> 
> 
> Could you add comment for above code? It's hard to understand the
> twice mapping if one did not follow the old thread.

Does that suffice:

/*
 * Make sure the 1:1 mappings are present as a catch-all for b0rked firmware
 * which doesn't update all internal pointers after switching to virtual mode
 * and would otherwise crap on us.
 */

?

Btw, when you reply to a mail, please remove that quoted portion of it
which you're not replying to - I had to scroll a bunch of screens down
and I almost missed your reply. :)

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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