linux-kernel - Re: [PATCH 5/8] kvm/mmu: make direct mapping paths aware of mapping levels

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 23 Jun 2009 19:10:22 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <marcelo@...ck.org>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8] kvm/mmu: make direct mapping paths aware of
	mapping levels

On Tue, Jun 23, 2009 at 01:47:28PM -0300, Marcelo Tosatti wrote:
> On Fri, Jun 19, 2009 at 03:16:26PM +0200, Joerg Roedel wrote:
> > @@ -254,7 +254,7 @@ static int is_last_spte(u64 pte, int level)
> >  {
> >  	if (level == PT_PAGE_TABLE_LEVEL)
> >  		return 1;
> > -	if (level == PT_DIRECTORY_LEVEL && is_large_pte(pte))
> > +	if (is_large_pte(pte))
> >  		return 1;
> 
> Wouldnt it be safer to check for bit 7 only on the levels
> we're sure it means large page?

If we are not on PT_PAGE_TABLE_LEVEL and this bit does not mean "large page"
then bit 7 is MBZ and harware would fault. So it should be safe to just check
for bit 7 here.


> >  	kvm_get_pfn(pfn);
> >  	mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0,
> > -		     gpte & PT_DIRTY_MASK, NULL, largepage,
> > +		     gpte & PT_DIRTY_MASK, NULL, level,
> >  		     gpte_to_gfn(gpte), pfn, true);
> 
> It would be better to just turn off updates to large sptes via          
> update_pte path, so just nuke them and let the pagefault path
> handle.

Yeah true. Thats in the shadow paging patch. Maybe I can get it into a state to
be postable again ;-)

Thanks,

	Joerg

-- 
           | Advanced Micro Devices GmbH
 Operating | Karl-Hammerschmidt-Str. 34, 85609 Dornach bei München
 System    | 
 Research  | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni
 Center    | Sitz: Dornach, Gemeinde Aschheim, Landkreis München
           | Registergericht München, HRB Nr. 43632

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/