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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: "Raj, Ashok" <ashok.raj@intel.com>,
	David Woodhouse <dwmw2@infradead.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Jonathan Cameron <jic23@kernel.org>
Subject: RE: [PATCH v7 03/11] iommu/vt-d: Add custom allocator for IOASID
Date: Fri, 25 Oct 2019 15:52:39 +0000
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D19D5D0FF0@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <e950cde8-8cd9-6089-c833-23d2ffb539d1@linux.intel.com>

> From: Lu Baolu [mailto:baolu.lu@linux.intel.com]
> Sent: Friday, October 25, 2019 10:39 PM
> 
> Hi,
> 
> On 10/25/19 2:40 PM, Tian, Kevin wrote:
> >>>> ioasid_register_allocator(&iommu->pasid_allocator);
> >>>> +			if (ret) {
> >>>> +				pr_warn("Custom PASID allocator
> >>>> registeration failed\n");
> >>>> +				/*
> >>>> +				 * Disable scalable mode on this
> >>>> IOMMU if there
> >>>> +				 * is no custom allocator. Mixing
> >>>> SM capable vIOMMU
> >>>> +				 * and non-SM vIOMMU are not
> >>>> supported.
> >>>> +				 */
> >>>> +				intel_iommu_sm = 0;
> >>> It's insufficient to disable scalable mode by only clearing
> >>> intel_iommu_sm. The DMA_RTADDR_SMT bit in root entry has already
> >> been
> >>> set. Probably, you need to
> >>>
> >>> for each iommu
> >>> 	clear DMA_RTADDR_SMT in root entry
> >>>
> >>> Alternatively, since vSVA is the only customer of this custom PASID
> >>> allocator, is it possible to only disable SVA here?
> >>>
> >> Yeah, I think disable SVA is better. We can still do gIOVA in SM. I
> >> guess we need to introduce a flag for sva_enabled.
> > I'm not sure whether tying above logic to SVA is the right approach.
> > If vcmd interface doesn't work, the whole SM mode doesn't make
> > sense which is based on PASID-granular protection (SVA is only one
> > usage atop). If the only remaining usage of SM is to map gIOVA using
> > reserved PASID#0, then why not disabling SM and just fallback to
> > legacy mode?
> >
> > Based on that I prefer to disabling the SM mode completely (better
> > through an interface), and move the logic out of CONFIG_INTEL_
> > IOMMU_SVM
> >
> 
> Unfortunately, it is dangerous to disable SM after boot. SM uses
> different root/device contexts and pasid table formats. Disabling SM
> after boot requires changing above from SM format into legacy format.

You are correct.

> 
> Since ioasid registration failure is a rare case. How about moving this
> part of code up to the early stage of intel_iommu_init() and returning
> error if hardware present vcmd capability but software fails to register
> a custom ioasid allocator?
> 

It makes sense to me.

Thanks
Kevin
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  reply index

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-24 19:54 [PATCH v7 00/11] Nested Shared Virtual Address (SVA) VT-d support Jacob Pan
2019-10-24 19:54 ` [PATCH v7 01/11] iommu/vt-d: Cache virtual command capability register Jacob Pan
2019-10-25  2:53   ` Lu Baolu
2019-10-25  6:06   ` Tian, Kevin
2019-11-08 10:32   ` Auger Eric
2019-10-24 19:54 ` [PATCH v7 02/11] iommu/vt-d: Enlightened PASID allocation Jacob Pan
2019-10-25  6:19   ` Tian, Kevin
2019-10-29 17:14     ` Jacob Pan
2019-10-29 18:16       ` Tian, Kevin
2019-11-08 10:33   ` Auger Eric
2019-11-08 22:22     ` Jacob Pan
2019-10-24 19:54 ` [PATCH v7 03/11] iommu/vt-d: Add custom allocator for IOASID Jacob Pan
2019-10-25  2:30   ` Lu Baolu
2019-10-25  4:43     ` Jacob Pan
2019-10-25  6:40       ` Tian, Kevin
2019-10-25 14:39         ` Lu Baolu
2019-10-25 15:52           ` Tian, Kevin [this message]
2019-10-28 22:49             ` Jacob Pan
2019-10-29  2:22               ` Lu Baolu
2019-10-25  6:31   ` Tian, Kevin
2019-10-28 22:52     ` Jacob Pan
2019-11-08 10:40   ` Auger Eric
2019-11-08 22:26     ` Jacob Pan
2019-10-24 19:54 ` [PATCH v7 04/11] iommu/vt-d: Replace Intel specific PASID allocator with IOASID Jacob Pan
2019-10-25  5:47   ` Lu Baolu
2019-11-01 18:29     ` Jacob Pan
2019-10-25  6:41   ` Tian, Kevin
2019-10-28 22:46     ` Jacob Pan
2019-11-08 11:30   ` Auger Eric
2019-11-08 22:55     ` Jacob Pan
2019-11-12  9:54       ` Auger Eric
2019-10-24 19:54 ` [PATCH v7 05/11] iommu/vt-d: Move domain helper to header Jacob Pan
2019-10-25  5:26   ` Lu Baolu
2019-10-24 19:54 ` [PATCH v7 06/11] iommu/vt-d: Avoid duplicated code for PASID setup Jacob Pan
2019-10-25  5:32   ` Lu Baolu
2019-10-25  6:42   ` Tian, Kevin
2019-10-28 22:41     ` Jacob Pan
2019-11-12  9:54   ` Auger Eric
2019-10-24 19:55 ` [PATCH v7 07/11] iommu/vt-d: Add nested translation helper function Jacob Pan
2019-10-25  7:04   ` Tian, Kevin
2019-11-01 21:10     ` Jacob Pan
2019-10-25 15:04   ` Lu Baolu
2019-10-25 16:06     ` Jacob Pan
2019-11-08 13:55   ` Auger Eric
2019-10-24 19:55 ` [PATCH v7 08/11] iommu/vt-d: Misc macro clean up for SVM Jacob Pan
2019-10-26  1:00   ` Lu Baolu
2019-10-28 22:38     ` Jacob Pan
2019-10-24 19:55 ` [PATCH v7 09/11] iommu/vt-d: Add bind guest PASID support Jacob Pan
2019-10-25  7:19   ` Tian, Kevin
2019-10-25 17:33     ` Jacob Pan
2019-10-28  6:03       ` Tian, Kevin
2019-10-28 16:02         ` Jacob Pan
2019-10-29  7:57           ` Tian, Kevin
2019-10-29 16:11             ` Jacob Pan
2019-10-29 18:04               ` Tian, Kevin
2019-10-29  2:33         ` Lu Baolu
2019-10-26  2:01   ` Lu Baolu
2019-10-28 22:29     ` Jacob Pan
2019-10-29  2:54       ` Lu Baolu
2019-10-29  4:11         ` Jacob Pan
2019-10-29  5:04           ` Lu Baolu
2019-10-24 19:55 ` [PATCH v7 10/11] iommu/vt-d: Support flushing more translation cache types Jacob Pan
2019-10-25  7:21   ` Tian, Kevin
2019-11-01 21:30     ` Jacob Pan
2019-10-26  2:22   ` Lu Baolu
2019-11-01 21:28     ` Jacob Pan
2019-11-08 16:18   ` Auger Eric
2019-11-08 23:05     ` Jacob Pan
2019-10-24 19:55 ` [PATCH v7 11/11] iommu/vt-d: Add svm/sva invalidate function Jacob Pan
2019-10-25  7:27   ` Tian, Kevin
2019-10-26  2:40     ` Lu Baolu
2019-10-26  7:03       ` Lu Baolu
2019-10-28  6:06         ` Tian, Kevin
2019-10-28 16:10           ` Jacob Pan
2019-10-29 18:52             ` Tian, Kevin
2019-10-29 19:25               ` Jacob Pan
2019-10-28 16:13     ` Jacob Pan
2019-11-12 10:28   ` Auger Eric

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