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Re: [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO
| To: | Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO mappings |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Tue, 09 Sep 2008 17:05:00 +0100 |
| Cc: | Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Avi Kivity <avi@xxxxxxxxxxxx>, Andi Kleen <andi@xxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx> |
| Delivery-date: | Tue, 09 Sep 2008 09:05:31 -0700 |
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| Thread-topic: | [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO mappings |
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On 9/9/08 16:48, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote: > Keir Fraser wrote: >> That's basically what our _PAGE_IO flag (in our old Linux patchset) means. >> We use it to cause pte_pfn() to return an invalid pfn and hence avoid >> reference counting that way. Since kernel mappings are never reference >> counted (I think?) perhaps we could use _PAGE_SPECIAL even if it is >> restricted to use on user mappings. > > Well, _PAGE_IOMAP's most important semantic from Xen's perspective is > that the frame number is considered to already be an MFN and so isn't > converted. It may be that _PAGE_SPECIAL is also useful for its "no > refcount" properties, but we could set both in that case. Oh, yes, our _PAGE_IO has the same meaning. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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