All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: "Liu, Yi L" <yi.l.liu@intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"stefanha@gmail.com" <stefanha@gmail.com>,
	"Sun, Yi Y" <yi.y.sun@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Robin Murphy <robin.murphy@arm.com>, "Wu, Hao" <hao.wu@intel.com>,
	Will Deacon <will@kernel.org>,
	"Tian, Jun J" <jun.j.tian@intel.com>
Subject: Re: [PATCH v5 03/15] iommu/smmu: Report empty domain nesting info
Date: Thu, 16 Jul 2020 17:39:59 +0200	[thread overview]
Message-ID: <20200716153959.GA447208@myrica> (raw)
In-Reply-To: <CY4PR11MB1432226D0A52D099249E95A0C3610@CY4PR11MB1432.namprd11.prod.outlook.com>

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...

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

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
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: "Liu, Yi L" <yi.l.liu@intel.com>
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, 16 Jul 2020 17:39:59 +0200	[thread overview]
Message-ID: <20200716153959.GA447208@myrica> (raw)
In-Reply-To: <CY4PR11MB1432226D0A52D099249E95A0C3610@CY4PR11MB1432.namprd11.prod.outlook.com>

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...

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

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

  reply	other threads:[~2020-07-16 15:40 UTC|newest]

Thread overview: 116+ 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 ` 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   ` Liu Yi L
2020-07-12 11:20 ` [PATCH v5 02/15] iommu: Report domain nesting info Liu Yi L
2020-07-12 11:20   ` Liu Yi L
2020-07-17 16:29   ` Auger Eric
2020-07-17 16:29     ` Auger Eric
2020-07-20  7:20     ` Liu, Yi L
2020-07-20  7:20       ` Liu, Yi L
2020-07-12 11:20 ` [PATCH v5 03/15] iommu/smmu: Report empty " Liu Yi L
2020-07-12 11:20   ` Liu Yi L
2020-07-13 13:14   ` Will Deacon
2020-07-13 13:14     ` Will Deacon
2020-07-14 10:12     ` Liu, Yi L
2020-07-14 10:12       ` Liu, Yi L
2020-07-16 15:39       ` Jean-Philippe Brucker [this message]
2020-07-16 15:39         ` Jean-Philippe Brucker
2020-07-16 20:38         ` Auger Eric
2020-07-16 20:38           ` Auger Eric
2020-07-17  9:09           ` Jean-Philippe Brucker
2020-07-17  9:09             ` Jean-Philippe Brucker
2020-07-17 10:28             ` Auger Eric
2020-07-17 10:28               ` Auger Eric
2020-07-23  9:44             ` Liu, Yi L
2020-07-23  9:44               ` Liu, Yi L
2020-07-23  9:40         ` Liu, Yi L
2020-07-23  9:40           ` Liu, Yi L
2020-07-17 17:18   ` Auger Eric
2020-07-17 17:18     ` Auger Eric
2020-07-20  7:26     ` Liu, Yi L
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
2020-07-12 11:20   ` Liu Yi L
2020-07-17 17:34   ` Auger Eric
2020-07-17 17:34     ` Auger Eric
2020-07-20  7:51     ` Liu, Yi L
2020-07-20  7:51       ` Liu, Yi L
2020-07-20  8:33       ` Auger Eric
2020-07-20  8:33         ` Auger Eric
2020-07-20  8:51         ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-19 15:38   ` Auger Eric
2020-07-19 15:38     ` Auger Eric
2020-07-20  8:03     ` Liu, Yi L
2020-07-20  8:03       ` Liu, Yi L
2020-07-20  8:26       ` Auger Eric
2020-07-20  8:26         ` Auger Eric
2020-07-20  8:49         ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-19 15:38   ` Auger Eric
2020-07-19 15:38     ` Auger Eric
2020-07-20  8:11     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-19 15:38   ` Auger Eric
2020-07-19 15:38     ` Auger Eric
2020-07-20  8:56     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-19 15:37   ` Auger Eric
2020-07-19 15:37     ` Auger Eric
2020-07-20  9:06     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-19 16:06   ` Auger Eric
2020-07-19 16:06     ` Auger Eric
2020-07-20 10:18     ` Liu, Yi L
2020-07-20 10:18       ` Liu, Yi L
2020-07-20 12:37       ` Auger Eric
2020-07-20 12:37         ` Auger Eric
2020-07-20 12:55         ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-20  9:37   ` Auger Eric
2020-07-20  9:37     ` Auger Eric
2020-07-20 10:37     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-20  9:41   ` Auger Eric
2020-07-20  9:41     ` Auger Eric
2020-07-20 10:42     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-20 12:22   ` Auger Eric
2020-07-20 12:22     ` Auger Eric
2020-07-23 12:05     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-20 12:35   ` Auger Eric
2020-07-20 12:35     ` Auger Eric
2020-07-20 13:00     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-18 13:39   ` Auger Eric
2020-07-18 13:39     ` Auger Eric
2020-07-25  8:54     ` Liu, Yi L
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
2020-07-12 11:21   ` Liu Yi L
2020-07-17 17:14   ` Auger Eric
2020-07-17 17:14     ` Auger Eric
2020-07-20 13:33     ` Liu, Yi L
2020-07-20 13:33       ` Liu, Yi L

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200716153959.GA447208@myrica \
    --to=jean-philippe@linaro.org \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=hao.wu@intel.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jun.j.tian@intel.com \
    --cc=kevin.tian@intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=stefanha@gmail.com \
    --cc=will@kernel.org \
    --cc=yi.l.liu@intel.com \
    --cc=yi.y.sun@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.