From: Ian Campbell <Ian.Campbell@citrix.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Konrad Rzeszutek Wilk <konrad@kernel.org>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jan Beulich <JBeulich@novell.com>,
"hpa@zytor.com" <hpa@zytor.com>
Subject: Re: [Xen-devel] Re: [PATCH 04/10] xen/mmu: For 1-1 mapping, automatically set _PAGE_IOMAP.
Date: Wed, 22 Dec 2010 16:27:24 +0000 [thread overview]
Message-ID: <1293035244.4500.3744.camel@zakaz.uk.xensource.com> (raw)
In-Reply-To: <20101222150258.GD1760@dumpdata.com>
On Wed, 2010-12-22 at 15:02 +0000, Konrad Rzeszutek Wilk wrote:
> On Tue, Dec 21, 2010 at 02:29:31PM -0800, Jeremy Fitzhardinge wrote:
> > On 12/21/2010 01:37 PM, Konrad Rzeszutek Wilk wrote:
> > > @@ -832,6 +832,9 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
> > > pteval_t flags = val & PTE_FLAGS_MASK;
> > > unsigned long mfn = pfn_to_mfn(pfn);
> > >
> > > + if (mfn == pfn)
> > > + flags |= _PAGE_IOMAP;
> >
> > Why? Does it really make sense to set _PAGE_IOMAP if they just happen
> > to be the same value?
>
> Yes. Without this, user applications, such as 'dmidecode' cannot get
> data.
I think Jeremy's point is that the "mfn == pfn" here has false
positives, since it is possible that a normal RAM page has identical mfn
and pfn by pure chance.
Ian.
next prev parent reply other threads:[~2010-12-22 16:28 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-21 21:37 [RFC PATCH v1] Consider void entries in the P2M as 1-1 mapping Konrad Rzeszutek Wilk
2010-12-21 21:37 ` [PATCH 01/10] xen: Make all reserved pages for the balloon be INVALID_P2M_ENTRY Konrad Rzeszutek Wilk
2010-12-21 22:19 ` Jeremy Fitzhardinge
2010-12-21 23:22 ` H. Peter Anvin
2010-12-22 8:47 ` [Xen-devel] " Ian Campbell
2010-12-22 14:53 ` Konrad Rzeszutek Wilk
2010-12-22 15:46 ` Jeremy Fitzhardinge
2010-12-21 21:37 ` [PATCH 02/10] xen/p2m: change p2m_missing_* to p2m_identity_* Konrad Rzeszutek Wilk
2010-12-21 22:41 ` Jeremy Fitzhardinge
2010-12-22 14:59 ` Konrad Rzeszutek Wilk
2010-12-22 20:36 ` Jeremy Fitzhardinge
2010-12-21 21:37 ` [PATCH 03/10] xen/mmu: Add the notion of IDENTITY_P2M_ENTRY Konrad Rzeszutek Wilk
2010-12-22 8:44 ` [Xen-devel] " Ian Campbell
2010-12-21 21:37 ` [PATCH 04/10] xen/mmu: For 1-1 mapping, automatically set _PAGE_IOMAP Konrad Rzeszutek Wilk
2010-12-21 22:29 ` Jeremy Fitzhardinge
2010-12-22 15:02 ` Konrad Rzeszutek Wilk
2010-12-22 16:27 ` Ian Campbell [this message]
2010-12-21 21:37 ` [PATCH 05/10] xen/setup: Set identity mapping for non-RAM E820 and E820 gaps Konrad Rzeszutek Wilk
2010-12-21 22:34 ` Jeremy Fitzhardinge
2010-12-22 15:04 ` Konrad Rzeszutek Wilk
2010-12-22 8:49 ` [Xen-devel] " Ian Campbell
2010-12-21 21:37 ` [PATCH 06/10] xen/setup: Only set identity mapping in E820 regions when privileged Konrad Rzeszutek Wilk
2010-12-21 22:37 ` Jeremy Fitzhardinge
2010-12-22 15:07 ` Konrad Rzeszutek Wilk
2010-12-21 21:37 ` [PATCH 07/10] xen/mmu: Work with 1-1 mappings when allocating new top/middle entries Konrad Rzeszutek Wilk
2010-12-21 22:37 ` Jeremy Fitzhardinge
2010-12-22 15:10 ` Konrad Rzeszutek Wilk
2010-12-22 8:54 ` [Xen-devel] " Ian Campbell
2010-12-22 17:47 ` Konrad Rzeszutek Wilk
2010-12-21 21:37 ` [PATCH 08/10] xen/mmu: Bugfix. Fill the top entry page with appropriate middle layer pointers Konrad Rzeszutek Wilk
2010-12-21 22:38 ` Jeremy Fitzhardinge
2010-12-22 15:11 ` Konrad Rzeszutek Wilk
2010-12-21 21:37 ` [PATCH 09/10] xen/mmu: Be aware of p2m_[mid_|]missing when saving/restore Konrad Rzeszutek Wilk
2010-12-21 21:37 ` [PATCH 10/10] xen/mmu: Warn against races Konrad Rzeszutek Wilk
2010-12-22 8:36 ` [Xen-devel] [RFC PATCH v1] Consider void entries in the P2M as 1-1 mapping Ian Campbell
2010-12-22 15:06 ` Konrad Rzeszutek Wilk
2010-12-22 16:26 ` Ian Campbell
2010-12-22 18:01 ` Konrad Rzeszutek Wilk
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