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From: Wei Liu <wei.liu2@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: wei.liu2@citrix.com, George.Dunlap@eu.citrix.com,
	andrew.cooper3@citrix.com, tim@xen.org, george.dunlap@citrix.com,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2] x86/p2m-pt: tighten conditions of IOMMU mapping updates
Date: Fri, 2 Oct 2015 10:16:05 +0100	[thread overview]
Message-ID: <20151002091605.GA25714@zion.uk.xensource.com> (raw)
In-Reply-To: <560E40E902000078000D9FFD@prv-mh.provo.novell.com>

On Fri, Oct 02, 2015 at 01:31:37AM -0600, Jan Beulich wrote:
> >>> George Dunlap <george.dunlap@citrix.com> 10/01/15 6:16 PM >>>
> >On 01/10/15 11:25, Jan Beulich wrote:
> >> TBD: As already mentioned on the large-page-MMIO-mapping patch, there
> >>      is an apparent inconsistency with PoD handling: 2M mappings get
> >>      valid entries created, while 4k mappings don't. It would seem to
> >>      me that the 4k case needs changing, even if today this may only
> >>      be a latent bug. Question of course is why we don't rely on
> >>      p2m_type_to_flags() doing its job properly and instead special
> >>      case certain P2M types.
> >
> >The inconsistency in the conditionals there is a bit strange; but I'm
> >pretty sure that in the 2MB case it is (at the moment) superfluous,
> >because at the moment it seems that when setting a page with type
> >p2m_populate_on_demand, it's always passing in _mfn(0), which is valid.
> >
> >(It used to pass a magic MFN, but Tim Deegan switched it to _mfn(0) at
> >some point without comment.)
> 
> Perhaps just because the magic MFN didn't always work? Tim?
> To me it looks wrong to pass anything other than INVALID_MFN
> there.
> 

I think George and you are talking about another function?  Is there
anything that prevents this patch from being committed as-is?

Wei.

> Jan
> 
> 

  reply	other threads:[~2015-10-02  9:16 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-01 10:25 [PATCH v2] x86/p2m-pt: tighten conditions of IOMMU mapping updates Jan Beulich
2015-10-01 13:34 ` Andrew Cooper
2015-10-01 14:36   ` Jan Beulich
2015-10-01 14:42     ` Andrew Cooper
2015-10-01 14:55 ` Wei Liu
2015-10-01 16:16 ` George Dunlap
2015-10-02  7:31   ` Jan Beulich
2015-10-02  9:16     ` Wei Liu [this message]
2015-10-02  9:25       ` Jan Beulich
2015-10-02  9:44       ` George Dunlap
2015-10-02  9:47     ` George Dunlap
2015-10-02 11:23       ` Jan Beulich
2015-10-02 12:19     ` Tim Deegan

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