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Re: [Xen-devel] [PATCH 1/6] x86/vtd: Don't include control register state in the table pointers

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxx>
  • From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • Date: Thu, 28 Feb 2019 05:54:26 +0000
  • Accept-language: en-US
  • Delivery-date: Thu, 28 Feb 2019 05:54:36 +0000
  • Dlp-product: dlpe-windows
  • Dlp-reaction: no-action
  • Dlp-version: 11.0.400.15
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AQHUyuLWZQt/iN6mvUa9+v02nWHM5qX0vjBQ
  • Thread-topic: [PATCH 1/6] x86/vtd: Don't include control register state in the table pointers

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Saturday, February 23, 2019 3:13 AM
> iremap_maddr and qinval_maddr point to the base of a block of contiguous
> RAM,
> allocated by the driver, holding the Interrupt Remapping table, and the
> Queued
> Invalidation ring.
> Despite their name, they are actually the values of the hardware register,
> including control metadata in the lower 12 bits.  While uses of these fields
> do appear to correctly shift out the metadata, this is very subtle behaviour
> and confusing to follow.
> Nothing uses the metadata, so make the fields actually point at the base of
> the relevant tables.
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Good catch!

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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