linux-kernel - Re: [PATCH] x86/efi: Always map boot service regions into new EFI page tables

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Date:	Mon, 14 Mar 2016 11:35:02 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Scott Ashcroft <scott.ashcroft@...k21.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Borislav Petkov <bp@...en8.de>,
	Ben Hutchings <ben@...adent.org.uk>,
	Raphael Hertzog <hertzog@...ian.org>,
	Roger Shimizu <rogershimizu@...il.com>,
	Alexis Murzeau <amurzeau@...il.com>
Subject: Re: [PATCH] x86/efi: Always map boot service regions into new EFI
 page tables

On Mon, 14 Mar, at 11:30:19AM, Ingo Molnar wrote:
> 
> * Matt Fleming <matt@...eblueprint.co.uk> wrote:
> 
> > diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
> > index 8fee5b6f8f66..af74849e8c0f 100644
> > --- a/arch/x86/mm/pageattr.c
> > +++ b/arch/x86/mm/pageattr.c
> > @@ -1055,7 +1055,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, pgd_t *pgd,
> >  	/*
> >  	 * Map everything starting from the Gb boundary, possibly with 1G pages
> >  	 */
> > -	while (end - start >= PUD_SIZE) {
> > +	while (cpu_has_gbpages && end - start >= PUD_SIZE) {
> >  		set_pud(pud, __pud(cpa->pfn << PAGE_SHIFT | _PAGE_PSE |
> >  				   massage_pgprot(pud_pgprot)));
> 
> Btw., can 'cpa->pfn << PAGE_SHIFT' possibly work on 32-bit systems?
> 
> cpa->pfn is unsigned long, so the result gets truncated to 32 bits ...
> 
> cpa->pfn should be u64.

That is a nice catch.

Note that we never run this code on 32-bit right now. Moving 32-bit to
this code and away from the old_map scheme is on my TODO list.