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RE: [Xen-devel] Third release of GPL'd PV drivers for Windows

To: "Samuel Thibault" <samuel.thibault@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Third release of GPL'd PV drivers for Windows
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Fri, 9 Nov 2007 23:20:19 +1100
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Thread-topic: [Xen-devel] Third release of GPL'd PV drivers for Windows
> James Harper, le Fri 09 Nov 2007 21:37:23 +1100, a écrit :
> > Windows appears to mostly give buffers aligned to a multiple of
> > 512 bytes (sector size) which may allow me to just grant Dom0 access to
> > the page... although what happens to the other bytes in the page?
> 
> They are untouched, so you can make the optimization, unless you are
> paranoid enough about information leakage and don't trust dom0.

Just tried it out. I'm not taking any metrics on how often the fast path is 
followed (eg how often Windows provides a buffer aligned to a 512 byte 
boundry), but some clock watching shows that an operation that takes 16-19 
seconds using the Qemu drivers takes 6-9 seconds using my PV drivers. The only 
issue so far is that while the PV drivers are doing their thing, Windows 
appears to get a bit starved for resources (appears to hang on occasion etc)... 
could be another bug causing that of course...

James

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