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[Xen-devel] RE: [PATCH][VTD][QUIRK] added quirks for Sandybridge errata

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH][VTD][QUIRK] added quirks for Sandybridge errata workaround, WLAN, VT-d fault escalation
From: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>
Date: Wed, 19 Jan 2011 15:40:55 -0800
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Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir@xxxxxxx>
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Thread-index: Acu3vS81+v6H0CemRy+hGqsopZ7mlAAdDUmQ
Thread-topic: [PATCH][VTD][QUIRK] added quirks for Sandybridge errata workaround, WLAN, VT-d fault escalation
> To me it would seem more logical to add a usage counter: When
> transitioning from zero, suppress RC6, and when transitioning to
> zero, re-enable RC6 (whatever this is). If what gets written in
> the preamble is some sort of counter the hardware decrements,
> you would need to extend the period each time execution flows
> through the preamble.

I see what you are getting at ...  Another alternative is to simply putting the 
lock around the "preamble->iotlb_flush->postamble" sequence in iommu.c.  It 
spills more of the quirk specific code into iommu.c but this should be much 
simpler logic wise.  What do you think?


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