From: Lu Baolu <baolu.lu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
To: Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Ashok Raj <ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Kevin Tian <kevin.tian-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Liu Yi L <yi.l.liu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Peter Xu <peterx-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Subject: Re: What is the meaning of PASID_MIN?
Date: Tue, 12 Feb 2019 10:44:23 +0800 [thread overview]
Message-ID: <0d86f3e8-60ec-5433-8602-487c8dc1ed83@linux.intel.com> (raw)
In-Reply-To: <20190211192804.GI12668-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
Hi,
On 2/12/19 3:28 AM, Matthew Wilcox wrote:
>
> I'm looking at commit 562831747f6299abd481b5b00bd4fa19d5c8a259
> which fails to adequately explain why we can't use PASID 0. Commit
> af39507305fb83a5d3c475c2851f4d59545d8a18 also doesn't explain why PASID
> 0 is no longer usable for the intel-svm driver.
Sorry that we didn't make it clear.
>
> There are a load of simplifications that could be made to this, but I
> don't know which ones to suggest without a clear understanding of the
> problem you're actually trying to solve.
>
PASID 0 has been reserved by Intel IOMMU driver for RID_PASID purpose.
VT-d scalable mode treats all address translation as PASID granularity.
For DMA requests-with-PASID, the PASID value in the DMA request will be
used. For DMA requests-without-PASID, VT-d will use a static PASID value
specified in the RID_PASID field of the context entry. PASID 0 has been
reserved for this usage for all devices.
(Please refer to 9.4 of the spec 3.0 for more details.)
Best regards,
Lu Baolu
next prev parent reply other threads:[~2019-02-12 2:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 19:28 What is the meaning of PASID_MIN? Matthew Wilcox
[not found] ` <20190211192804.GI12668-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2019-02-12 2:44 ` Lu Baolu [this message]
[not found] ` <0d86f3e8-60ec-5433-8602-487c8dc1ed83-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2019-02-12 3:02 ` Peter Xu
2019-02-12 3:13 ` Lu Baolu
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