netdev - Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p

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]

Message-ID: <alpine.DEB.2.02.1401231355340.15917@kaball.uk.xensource.com>
Date:	Thu, 23 Jan 2014 13:59:07 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	<ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <jonathan.davies@...rix.com>
Subject: Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p_override during
 mapping

On Wed, 22 Jan 2014, Zoltan Kiss wrote:
> > > > > diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> > > > > index 2ae8699..0060178 100644
> > > > > --- a/arch/x86/xen/p2m.c
> > > > > +++ b/arch/x86/xen/p2m.c
> > > > > @@ -872,15 +872,13 @@ static unsigned long mfn_hash(unsigned long mfn)
> > > > > 
> > > > >    /* Add an MFN override for a particular page */
> > > > >    int m2p_add_override(unsigned long mfn, struct page *page,
> > > > > -		struct gnttab_map_grant_ref *kmap_op)
> > > > > +		struct gnttab_map_grant_ref *kmap_op, unsigned long
> > > > > pfn)
> > > > 
> > > > Do we really need to add another additional parameter to
> > > > m2p_add_override?
> > > > I would just let m2p_add_override and m2p_remove_override call
> > > > page_to_pfn again. It is not that expensive.
> > > Yes, because that page_to_pfn can return something different. That's why
> > > the
> > > v2 patches failed.
> > 
> > I am really curious: how can page_to_pfn return something different?
> > I don't think is supposed to happen.
> You call set_phys_to_machine before calling m2p* functions.

set_phys_to_machine changes the physical to machine mapping, that would
be the mfn corresponding to a given pfn. It shouldn't affect the output
of page_to_pfn that returns the pfn corresponding to a given struct
page. The calculation of which is based on address offsets and should be
static and unaffected by things like set_phys_to_machine.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html