From: Lu Baolu <baolu.lu@linux.intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: baolu.lu@linux.intel.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Joerg Roedel <joro@8bytes.org>,
Alex Williamson <alex.williamson@redhat.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Christoph Hellwig <hch@infradead.org>,
Kevin Tian <kevin.tian@intel.com>,
Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Dan Williams <dan.j.williams@intel.com>,
rafael@kernel.org, Diana Craciun <diana.craciun@oss.nxp.com>,
Cornelia Huck <cohuck@redhat.com>,
Eric Auger <eric.auger@redhat.com>, Liu Yi L <yi.l.liu@intel.com>,
Jacob jun Pan <jacob.jun.pan@intel.com>,
Chaitanya Kulkarni <kch@nvidia.com>,
Stuart Yoder <stuyoder@gmail.com>,
Laurentiu Tudor <laurentiu.tudor@nxp.com>,
Thierry Reding <thierry.reding@gmail.com>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Jonathan Hunter <jonathanh@nvidia.com>,
Li Yang <leoyang.li@nxp.com>, Dmitry Osipenko <digetx@gmail.com>,
iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 09/14] PCI: portdrv: Suppress kernel DMA ownership auto-claiming
Date: Fri, 7 Jan 2022 09:53:54 +0800 [thread overview]
Message-ID: <1545319f-130e-3750-ea00-082a12b73852@linux.intel.com> (raw)
In-Reply-To: <20220106183224.GA298861@bhelgaas>
On 1/7/22 2:32 AM, Bjorn Helgaas wrote:
> On Thu, Jan 06, 2022 at 12:12:35PM +0800, Lu Baolu wrote:
>> On 1/5/22 1:06 AM, Bjorn Helgaas wrote:
>>> On Tue, Jan 04, 2022 at 09:56:39AM +0800, Lu Baolu wrote:
>>>> If a switch lacks ACS P2P Request Redirect, a device below the switch can
>>>> bypass the IOMMU and DMA directly to other devices below the switch, so
>>>> all the downstream devices must be in the same IOMMU group as the switch
>>>> itself.
>>> Help me think through what's going on here. IIUC, we put devices in
>>> the same IOMMU group when they can interfere with each other in any
>>> way (DMA, config access, etc).
>>>
>>> (We said "DMA" above, but I guess this would also apply to config
>>> requests, right?)
>>
>> I am not sure whether devices could interfere each other through config
>> space access. The IOMMU hardware only protects and isolates DMA
>> accesses, so that userspace could control DMA directly. The config
>> accesses will always be intercepted by VFIO. Hence, I don't see a
>> problem.
>
> I was wondering about config accesses generated by an endpoint, e.g.,
> an endpoint doing config writes to a peer or the upstream bridge.
>
> But I think that is prohibited by spec - PCIe r5.0, sec 7.3.3, says
> "Propagation of Configuration Requests from Downstream to Upstream as
> well as peer-to-peer are not supported" and "Configuration Requests
> are initiated only by the Host Bridge, including those passed through
> the SFI CAM mechanism."
That's clear. Thank you for the clarification.
>
> Bjorn
>
Best regards,
baolu
next prev parent reply other threads:[~2022-01-07 1:54 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-04 1:56 [PATCH v5 00/14] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu
2022-01-04 1:56 ` [PATCH v5 01/14] iommu: Add dma ownership management interfaces Lu Baolu
2022-01-04 10:08 ` Christoph Hellwig
2022-01-04 16:41 ` Bjorn Helgaas
2022-01-04 19:23 ` Jason Gunthorpe
2022-01-06 3:18 ` Lu Baolu
2022-01-06 3:54 ` Lu Baolu
2022-01-06 15:46 ` Jason Gunthorpe
2022-01-07 1:50 ` Lu Baolu
2022-01-06 3:43 ` Lu Baolu
2022-01-06 3:47 ` Lu Baolu
2022-01-06 3:51 ` Lu Baolu
2022-01-05 6:57 ` Lu Baolu
2022-01-04 1:56 ` [PATCH v5 02/14] driver core: Add dma_cleanup callback in bus_type Lu Baolu
2022-01-04 10:08 ` Christoph Hellwig
2022-01-04 12:39 ` Jason Gunthorpe
2022-01-04 13:04 ` Greg Kroah-Hartman
2022-02-08 5:55 ` Lu Baolu
2022-02-08 11:35 ` Greg Kroah-Hartman
2022-02-14 10:01 ` Greg Kroah-Hartman
2022-02-14 10:02 ` Greg Kroah-Hartman
2022-01-04 1:56 ` [PATCH v5 03/14] amba: Stop sharing platform_dma_configure() Lu Baolu
2022-01-04 1:56 ` [PATCH v5 04/14] driver core: platform: Add driver dma ownership management Lu Baolu
2022-02-14 9:59 ` Greg Kroah-Hartman
2022-02-14 13:18 ` Jason Gunthorpe
2022-02-14 13:37 ` Greg Kroah-Hartman
2022-02-14 13:43 ` Jason Gunthorpe
2022-01-04 1:56 ` [PATCH v5 05/14] amba: " Lu Baolu
2022-01-04 1:56 ` [PATCH v5 06/14] bus: fsl-mc: " Lu Baolu
2022-01-04 1:56 ` [PATCH v5 07/14] PCI: " Lu Baolu
2022-02-14 10:03 ` Greg Kroah-Hartman
2022-02-14 12:38 ` Jason Gunthorpe
2022-02-14 12:51 ` Greg Kroah-Hartman
2022-02-14 13:11 ` Jason Gunthorpe
2022-02-14 13:39 ` Greg Kroah-Hartman
2022-02-14 13:43 ` Jason Gunthorpe
2022-02-15 3:06 ` Lu Baolu
2022-02-23 18:00 ` Bjorn Helgaas
2022-02-23 18:07 ` Jason Gunthorpe
2022-01-04 1:56 ` [PATCH v5 08/14] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming Lu Baolu
2022-01-04 1:56 ` [PATCH v5 09/14] PCI: portdrv: " Lu Baolu
2022-01-04 17:06 ` Bjorn Helgaas
2022-01-04 19:26 ` Jason Gunthorpe
2022-01-04 19:51 ` Bjorn Helgaas
2022-01-05 0:35 ` Jason Gunthorpe
2022-01-06 4:12 ` Lu Baolu
2022-01-06 18:32 ` Bjorn Helgaas
2022-01-07 1:53 ` Lu Baolu [this message]
2022-01-04 1:56 ` [PATCH v5 10/14] vfio: Set DMA ownership for VFIO devices Lu Baolu
2022-01-04 1:56 ` [PATCH v5 11/14] vfio: Remove use of vfio_group_viable() Lu Baolu
2022-01-04 1:56 ` [PATCH v5 12/14] vfio: Delete the unbound_list Lu Baolu
2022-01-04 1:56 ` [PATCH v5 13/14] vfio: Remove iommu group notifier Lu Baolu
2022-01-04 1:56 ` [PATCH v5 14/14] iommu: Remove iommu group changes notifier Lu Baolu
2022-01-04 12:48 ` [PATCH v5 00/14] Fix BUG_ON in vfio_iommu_group_notifier() Jason Gunthorpe
2022-01-05 6:52 ` Lu Baolu
2022-02-18 1:07 ` Lu Baolu
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=1545319f-130e-3750-ea00-082a12b73852@linux.intel.com \
--to=baolu.lu@linux.intel.com \
--cc=airlied@linux.ie \
--cc=alex.williamson@redhat.com \
--cc=ashok.raj@intel.com \
--cc=bhelgaas@google.com \
--cc=cohuck@redhat.com \
--cc=dan.j.williams@intel.com \
--cc=daniel@ffwll.ch \
--cc=diana.craciun@oss.nxp.com \
--cc=digetx@gmail.com \
--cc=eric.auger@redhat.com \
--cc=gregkh@linuxfoundation.org \
--cc=hch@infradead.org \
--cc=helgaas@kernel.org \
--cc=iommu@lists.linux-foundation.org \
--cc=jacob.jun.pan@intel.com \
--cc=jgg@nvidia.com \
--cc=jonathanh@nvidia.com \
--cc=joro@8bytes.org \
--cc=kch@nvidia.com \
--cc=kevin.tian@intel.com \
--cc=kvm@vger.kernel.org \
--cc=laurentiu.tudor@nxp.com \
--cc=leoyang.li@nxp.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=rafael@kernel.org \
--cc=robin.murphy@arm.com \
--cc=stuyoder@gmail.com \
--cc=thierry.reding@gmail.com \
--cc=will@kernel.org \
--cc=yi.l.liu@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 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).