From: "Tian, Kevin" <kevin.tian@intel.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Baolu Lu <baolu.lu@linux.intel.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"Liu, Yi L" <yi.l.liu@intel.com>, Joerg Roedel <joro@8bytes.org>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 2/2] iommu/vt-d: Remove caching mode check before devtlb flush
Date: Fri, 12 Apr 2024 03:13:33 +0000 [thread overview]
Message-ID: <BN9PR11MB5276A2DFFA8C523EA1C148968C042@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20240411091749.20afae6b@jacob-builder>
> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Sent: Friday, April 12, 2024 12:18 AM
>
> Hi Kevin,
>
> On Wed, 10 Apr 2024 23:23:57 +0000, "Tian, Kevin" <kevin.tian@intel.com>
> wrote:
>
> > > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > Sent: Thursday, April 11, 2024 12:20 AM
> > >
> > > Hi Kevin,
> > >
> > > On Wed, 10 Apr 2024 00:32:06 +0000, "Tian, Kevin"
> <kevin.tian@intel.com>
> > > wrote:
> > >
> > > > > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > > > Sent: Wednesday, April 10, 2024 1:32 AM
> > > > >
> > > > > If the guest uses SL page tables in vIOMMU, we don;t expose ATS to
> > > > > the guest. So ATS is not relevant here, does't matter map or unmap.
> > > > >
> > > >
> > > > ATS is orthogonal to SL vs. FL. Where is this restriction coming
> > > > from?
> > > For practical purposes, what would be the usage to have SL in the guest
> > > and ATS enabled. i.e. shadowing SL but directly expose ATS?
> > >
> >
> > ATS is about the protocol between device and iommu to look up
> > translations. Why does it care about internal paging layout in
> > iommu?
> >
> Maybe the original intent was missed, I was suggesting the devTLB flush
> should be based on ATS cap (as you said here) not map/unmap.
>
> - /*
> - * In caching mode, changes of pages from non-present to present
> require
> - * flush. However, device IOTLB doesn't need to be flushed in this case.
> - */
> - if (!cap_caching_mode(iommu->cap) || !map)
> - iommu_flush_dev_iotlb(domain, addr, mask);
> + iommu_flush_dev_iotlb(domain, addr, mask);
>
We need check both, as devtlb doesn't cache non-present
so the invalidation is required only for unmap.
Here just the check of caching mode is irrelevant.
next prev parent reply other threads:[~2024-04-12 3:13 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-07 14:42 [PATCH 1/2] iommu/vt-d: Avoid unnecessary device TLB flush in map path Lu Baolu
2024-04-07 14:42 ` [PATCH 2/2] iommu/vt-d: Remove caching mode check before devtlb flush Lu Baolu
2024-04-08 7:21 ` Ethan Zhao
2024-04-08 7:23 ` Baolu Lu
2024-04-08 7:43 ` Ethan Zhao
2024-04-08 21:03 ` Jacob Pan
2024-04-09 3:12 ` Baolu Lu
2024-04-09 17:31 ` Jacob Pan
2024-04-10 0:32 ` Tian, Kevin
2024-04-10 16:19 ` Jacob Pan
2024-04-10 23:23 ` Tian, Kevin
2024-04-11 16:17 ` Jacob Pan
2024-04-12 3:13 ` Tian, Kevin [this message]
2024-04-09 7:30 ` Tian, Kevin
2024-04-10 5:40 ` Baolu Lu
2024-04-10 23:49 ` Zhang, Tina
2024-04-11 12:15 ` Baolu Lu
2024-04-09 8:36 ` Yi Liu
2024-04-09 7:20 ` [PATCH 1/2] iommu/vt-d: Avoid unnecessary device TLB flush in map path Tian, Kevin
2024-04-09 7:21 ` Tian, Kevin
2024-04-09 8:27 ` Yi Liu
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