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From: "Liu, Yi L" <yi.l.liu@intel.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Will Deacon <will@kernel.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"eric.auger@redhat.com" <eric.auger@redhat.com>,
	"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	"jacob.jun.pan@linux.intel.com" <jacob.jun.pan@linux.intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	"Tian, Jun J" <jun.j.tian@intel.com>,
	"Sun, Yi Y" <yi.y.sun@intel.com>,
	"peterx@redhat.com" <peterx@redhat.com>,
	"Wu, Hao" <hao.wu@intel.com>,
	"stefanha@gmail.com" <stefanha@gmail.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Robin Murphy <robin.murphy@arm.com>
Subject: RE: [PATCH v5 03/15] iommu/smmu: Report empty domain nesting info
Date: Thu, 23 Jul 2020 09:40:42 +0000	[thread overview]
Message-ID: <DM5PR11MB1435B0B62ABD24F06A4D5BF2C3760@DM5PR11MB1435.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20200716153959.GA447208@myrica>

Hi Jean,

> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Sent: Thursday, July 16, 2020 11:40 PM
> 
> On Tue, Jul 14, 2020 at 10:12:49AM +0000, Liu, Yi L wrote:
> > > Have you verified that this doesn't break the existing usage of
> > > DOMAIN_ATTR_NESTING in drivers/vfio/vfio_iommu_type1.c?
> >
> > I didn't have ARM machine on my hand. But I contacted with Jean
> > Philippe, he confirmed no compiling issue. I didn't see any code
> > getting DOMAIN_ATTR_NESTING attr in current drivers/vfio/vfio_iommu_type1.c.
> > What I'm adding is to call iommu_domai_get_attr(, DOMAIN_ATTR_NESTIN)
> > and won't fail if the iommu_domai_get_attr() returns 0. This patch
> > returns an empty nesting info for DOMAIN_ATTR_NESTIN and return
> > value is 0 if no error. So I guess it won't fail nesting for ARM.
> 
> I confirm that this series doesn't break the current support for
> VFIO_IOMMU_TYPE1_NESTING with an SMMUv3. That said...

thanks.

> If the SMMU does not support stage-2 then there is a change in behavior
> (untested): after the domain is silently switched to stage-1 by the SMMU
> driver, VFIO will now query nesting info and obtain -ENODEV. Instead of
> succeding as before, the VFIO ioctl will now fail. I believe that's a fix
> rather than a regression, it should have been like this since the
> beginning. No known userspace has been using VFIO_IOMMU_TYPE1_NESTING so
> far, so I don't think it should be a concern.
> 
> And if userspace queries the nesting properties using the new ABI
> introduced in this patchset, it will obtain an empty struct.

yes.

> I think
> that's acceptable, but it may be better to avoid adding the nesting cap if
> @format is 0?

right. will add it in patch 4/15.

Regards,
Yi Liu

> 
> Thanks,
> Jean
> 
> >
> > @Eric, how about your opinion? your dual-stage vSMMU support may
> > also share the vfio_iommu_type1.c code.
> >
> > Regards,
> > Yi Liu
> >
> > > Will

  parent reply	other threads:[~2020-07-23  9:40 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-12 11:20 [PATCH v5 00/15] vfio: expose virtual Shared Virtual Addressing to VMs Liu Yi L
2020-07-12 11:20 ` [PATCH v5 01/15] vfio/type1: Refactor vfio_iommu_type1_ioctl() Liu Yi L
2020-07-12 11:20 ` [PATCH v5 02/15] iommu: Report domain nesting info Liu Yi L
2020-07-17 16:29   ` Auger Eric
2020-07-20  7:20     ` Liu, Yi L
2020-07-12 11:20 ` [PATCH v5 03/15] iommu/smmu: Report empty " Liu Yi L
2020-07-13 13:14   ` Will Deacon
2020-07-14 10:12     ` Liu, Yi L
2020-07-16 15:39       ` Jean-Philippe Brucker
2020-07-16 20:38         ` Auger Eric
2020-07-17  9:09           ` Jean-Philippe Brucker
2020-07-17 10:28             ` Auger Eric
2020-07-23  9:44             ` Liu, Yi L
2020-07-23  9:40         ` Liu, Yi L [this message]
2020-07-17 17:18   ` Auger Eric
2020-07-20  7:26     ` Liu, Yi L
2020-07-12 11:20 ` [PATCH v5 04/15] vfio/type1: Report iommu nesting info to userspace Liu Yi L
2020-07-17 17:34   ` Auger Eric
2020-07-20  7:51     ` Liu, Yi L
2020-07-20  8:33       ` Auger Eric
2020-07-20  8:51         ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 05/15] vfio: Add PASID allocation/free support Liu Yi L
2020-07-19 15:38   ` Auger Eric
2020-07-20  8:03     ` Liu, Yi L
2020-07-20  8:26       ` Auger Eric
2020-07-20  8:49         ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 06/15] iommu/vt-d: Support setting ioasid set to domain Liu Yi L
2020-07-19 15:38   ` Auger Eric
2020-07-20  8:11     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 07/15] vfio/type1: Add VFIO_IOMMU_PASID_REQUEST (alloc/free) Liu Yi L
2020-07-19 15:38   ` Auger Eric
2020-07-20  8:56     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 08/15] iommu: Pass domain to sva_unbind_gpasid() Liu Yi L
2020-07-19 15:37   ` Auger Eric
2020-07-20  9:06     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 09/15] iommu/vt-d: Check ownership for PASIDs from user-space Liu Yi L
2020-07-19 16:06   ` Auger Eric
2020-07-20 10:18     ` Liu, Yi L
2020-07-20 12:37       ` Auger Eric
2020-07-20 12:55         ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 10/15] vfio/type1: Support binding guest page tables to PASID Liu Yi L
2020-07-20  9:37   ` Auger Eric
2020-07-20 10:37     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 11/15] vfio/type1: Allow invalidating first-level/stage IOMMU cache Liu Yi L
2020-07-20  9:41   ` Auger Eric
2020-07-20 10:42     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 12/15] vfio/type1: Add vSVA support for IOMMU-backed mdevs Liu Yi L
2020-07-20 12:22   ` Auger Eric
2020-07-23 12:05     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 13/15] vfio/pci: Expose PCIe PASID capability to guest Liu Yi L
2020-07-20 12:35   ` Auger Eric
2020-07-20 13:00     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 14/15] vfio: Document dual stage control Liu Yi L
2020-07-18 13:39   ` Auger Eric
2020-07-25  8:54     ` Liu, Yi L
2020-07-12 11:21 ` [PATCH v5 15/15] iommu/vt-d: Support reporting nesting capability info Liu Yi L
2020-07-17 17:14   ` Auger Eric
2020-07-20 13:33     ` Liu, Yi L

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