linux-kernel - Re: [PATCH] x86/setup: fix low identity map for >= 2GB kernel range

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Message-ID: <20151107094306.GA2387@codeblueprint.co.uk>
Date:	Sat, 7 Nov 2015 09:43:06 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Krzysztof Mazur <krzysiek@...lesie.net>
Cc:	Borislav Petkov <bp@...en8.de>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Laszlo Ersek <lersek@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/setup: fix low identity map for >= 2GB kernel range

On Fri, 06 Nov, at 03:11:39PM, Krzysztof Mazur wrote:
> On Fri, Nov 06, 2015 at 02:27:33PM +0100, Borislav Petkov wrote:
> > On Fri, Nov 06, 2015 at 02:18:36PM +0100, Krzysztof Mazur wrote:
> > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> > > index a3cccbf..37c8ea8 100644
> > > --- a/arch/x86/kernel/setup.c
> > > +++ b/arch/x86/kernel/setup.c
> > > @@ -1180,7 +1180,7 @@ void __init setup_arch(char **cmdline_p)
> > >  	 */
> > >  	clone_pgd_range(initial_page_table,
> > >  			swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
> > > -			KERNEL_PGD_PTRS);
> > > +			min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
> > >  #endif
> > >  
> > >  	tboot_probe();
> > 
> > http://git.kernel.org/tip/1c5dac914794f0170e1582d8ffdee52d30e0e4dd
> > 
> 
> Thanks and sorry. Yes, it has been already fixed. I've rechecked only
> mainline.
> 
> However, I think that there should be
> min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY), not just KERNEL_PGD_BOUNDARY
> (usually 768 for normal 1G/3G split), because swapper_pg_dir has only
> 1024 entries and 768+768 is 1536.

Yeah, this fix is preferable to the one that is currently sitting in
tip/x86/urgent. Curse you VMSPLIT!
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