linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alex Williamson <alex.williamson@redhat.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>,
	Don Dutile <ddutile@redhat.com>,
	Eric Auger <eric.auger@redhat.com>,
	eric.auger.pro@gmail.com, marc.zyngier@arm.com,
	robin.murphy@arm.com, joro@8bytes.org, tglx@linutronix.de,
	jason@lakedaemon.net, linux-arm-kernel@lists.infradead.org,
	kvm@vger.kernel.org, drjones@redhat.com,
	linux-kernel@vger.kernel.org, pranav.sawargaonkar@gmail.com,
	iommu@lists.linux-foundation.org, punit.agrawal@arm.com,
	diana.craciun@nxp.com, benh@kernel.crashing.org, arnd@arndb.de,
	jcm@redhat.com, dwmw@amazon.co.uk
Subject: Re: Summary of LPC guest MSI discussion in Santa Fe
Date: Wed, 9 Nov 2016 15:17:09 -0700	[thread overview]
Message-ID: <20161109151709.74927f83@t450s.home> (raw)
In-Reply-To: <20161109203145.GO17771@arm.com>

On Wed, 9 Nov 2016 20:31:45 +0000
Will Deacon <will.deacon@arm.com> wrote:
> On Wed, Nov 09, 2016 at 08:23:03PM +0100, Christoffer Dall wrote:
> > 
> > (I suppose it's technically possible to get around this issue by letting
> > QEMU place RAM wherever it wants but tell the guest to never use a
> > particular subset of its RAM for DMA, because that would conflict with
> > the doorbell IOVA or be seen as p2p transactions.  But I think we all
> > probably agree that it's a disgusting idea.)  
> 
> Disgusting, yes, but Ben's idea of hotplugging on the host controller with
> firmware tables describing the reserved regions is something that we could
> do in the distant future. In the meantime, I don't think that VFIO should
> explicitly reject overlapping mappings if userspace asks for them.

I'm confused by the last sentence here, rejecting user mappings that
overlap reserved ranges, such as MSI doorbell pages, is exactly how
we'd reject hot-adding a device when we meet such a conflict.  If we
don't reject such a mapping, we're knowingly creating a situation that
potentially leads to data loss.  Minimally, QEMU would need to know
about the reserved region, map around it through VFIO, and take
responsibility (somehow) for making sure that region is never used for
DMA.  Thanks,

Alex

  reply	other threads:[~2016-11-09 22:17 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-03 21:39 [RFC 0/8] KVM PCIe/MSI passthrough on ARM/ARM64 (Alt II) Eric Auger
2016-11-03 21:39 ` [RFC 1/8] vfio: fix vfio_info_cap_add/shift Eric Auger
2016-11-03 21:39 ` [RFC 2/8] iommu/iova: fix __alloc_and_insert_iova_range Eric Auger
2016-11-03 21:39 ` [RFC 3/8] iommu/dma: Allow MSI-only cookies Eric Auger
2016-11-03 21:39 ` [RFC 4/8] iommu: Add a list of iommu_reserved_region in iommu_domain Eric Auger
2016-11-03 21:39 ` [RFC 5/8] vfio/type1: Introduce RESV_IOVA_RANGE capability Eric Auger
2016-11-03 21:39 ` [RFC 6/8] iommu: Handle the list of reserved regions Eric Auger
2016-11-03 21:39 ` [RFC 7/8] iommu/vt-d: Implement add_reserved_regions callback Eric Auger
2016-11-03 21:39 ` [RFC 8/8] iommu/arm-smmu: implement " Eric Auger
2016-11-04  4:02 ` [RFC 0/8] KVM PCIe/MSI passthrough on ARM/ARM64 (Alt II) Alex Williamson
2016-11-08  2:45   ` Summary of LPC guest MSI discussion in Santa Fe (was: Re: [RFC 0/8] KVM PCIe/MSI passthrough on ARM/ARM64 (Alt II)) Will Deacon
2016-11-08 14:27     ` Summary of LPC guest MSI discussion in Santa Fe Auger Eric
2016-11-08 17:54       ` Will Deacon
2016-11-08 19:02         ` Don Dutile
2016-11-08 19:10           ` Will Deacon
2016-11-09  7:43           ` Auger Eric
2016-11-08 16:02     ` Don Dutile
2016-11-08 20:29     ` Summary of LPC guest MSI discussion in Santa Fe (was: Re: [RFC 0/8] KVM PCIe/MSI passthrough on ARM/ARM64 (Alt II)) Christoffer Dall
2016-11-08 23:35       ` Alex Williamson
2016-11-09  2:52         ` Summary of LPC guest MSI discussion in Santa Fe Don Dutile
2016-11-09 17:03           ` Will Deacon
2016-11-09 18:59             ` Don Dutile
2016-11-09 19:23               ` Christoffer Dall
2016-11-09 20:01                 ` Alex Williamson
2016-11-10 14:40                   ` Joerg Roedel
2016-11-10 17:07                     ` Alex Williamson
2016-11-09 20:31                 ` Will Deacon
2016-11-09 22:17                   ` Alex Williamson [this message]
2016-11-09 22:25                     ` Will Deacon
2016-11-09 23:24                       ` Alex Williamson
2016-11-09 23:38                         ` Will Deacon
2016-11-09 23:59                           ` Alex Williamson
2016-11-10  0:14                             ` Auger Eric
2016-11-10  0:55                               ` Alex Williamson
2016-11-10  2:01                                 ` Will Deacon
2016-11-10 11:14                                   ` Auger Eric
2016-11-10 17:46                                     ` Alex Williamson
2016-11-11 11:19                                       ` Joerg Roedel
2016-11-11 15:50                                         ` Alex Williamson
2016-11-11 16:05                                           ` Alex Williamson
2016-11-14 15:19                                             ` Joerg Roedel
2016-11-11 16:25                                           ` Don Dutile
2016-11-11 16:00                                         ` Don Dutile
2016-11-10 14:52                               ` Joerg Roedel
2016-11-09 20:11               ` Robin Murphy
2016-11-10 15:18                 ` Joerg Roedel
2016-11-21  5:13     ` Jon Masters
2016-11-23 20:12       ` Don Dutile

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=20161109151709.74927f83@t450s.home \
    --to=alex.williamson@redhat.com \
    --cc=arnd@arndb.de \
    --cc=benh@kernel.crashing.org \
    --cc=christoffer.dall@linaro.org \
    --cc=ddutile@redhat.com \
    --cc=diana.craciun@nxp.com \
    --cc=drjones@redhat.com \
    --cc=dwmw@amazon.co.uk \
    --cc=eric.auger.pro@gmail.com \
    --cc=eric.auger@redhat.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jason@lakedaemon.net \
    --cc=jcm@redhat.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=marc.zyngier@arm.com \
    --cc=pranav.sawargaonkar@gmail.com \
    --cc=punit.agrawal@arm.com \
    --cc=robin.murphy@arm.com \
    --cc=tglx@linutronix.de \
    --cc=will.deacon@arm.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).