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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: Tue, 18 Jan 2011 16:12:07 -0800
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Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir@xxxxxxx>
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Thread-index: Acu29OxhIDRLEHH8QbCnuezi7WB+WAAdycaA
Thread-topic: [PATCH][VTD][QUIRK] added quirks for Sandybridge errata workaround, WLAN, VT-d fault escalation
> Isn't there a risk that these MMIO writes interfere with the
> operation of the actual driver running in a domain?

I have checked drivers/gpu/drm/i915/i915_reg.h in the kernel and I don't see 
any usage of these MMIO registers.  Do you think we should add a boot switch to 
allow optionally turn off these workarounds just in case?  If so, what default 
value should it be?

> And even just in Xen itself, how do these writes get
> synchronized? Callers of vtd_ops_preamble_quirk() don't
> appear to be required to hold any particular lock.

I have added a igd_lock in the attached patch.  Can you take a look?


Attachment: lock.patch
Description: lock.patch

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