From: Doug Anderson <dianders@chromium.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <joro@8bytes.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Ulf Hansson <ulf.hansson@linaro.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Rob Clark <robdclark@chromium.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
linux-pci@vger.kernel.org, quic_c_gdjako@quicinc.com,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,"
<iommu@lists.linux-foundation.org>,
Sonny Rao <sonnyrao@chromium.org>,
Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Linux MMC List <linux-mmc@vger.kernel.org>,
Veerabhadrarao Badiganti <vbadigan@codeaurora.org>,
Rajat Jain <rajatja@google.com>,
Saravana Kannan <saravanak@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/6] PCI: Indicate that we want to force strict DMA for untrusted devices
Date: Thu, 24 Jun 2021 06:46:50 -0700 [thread overview]
Message-ID: <CAD=FV=VQEM=Gtzrkd-s_ufzi_Y7b1GPCOVROftmjLDWiMEd0qA@mail.gmail.com> (raw)
In-Reply-To: <YNSKyu/a8S3Qywbc@kroah.com>
Hi,
On Thu, Jun 24, 2021 at 6:38 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Mon, Jun 21, 2021 at 04:52:45PM -0700, Douglas Anderson wrote:
> > At the moment the generic IOMMU framework reaches into the PCIe device
> > to check the "untrusted" state and uses this information to figure out
> > if it should be running the IOMMU in strict or non-strict mode. Let's
> > instead set the new boolean in "struct device" to indicate when we
> > want forced strictness.
> >
> > NOTE: we still continue to set the "untrusted" bit in PCIe since that
> > apparently is used for more than just IOMMU strictness. It probably
> > makes sense for a later patchset to clarify all of the other needs we
> > have for "untrusted" PCIe devices (perhaps add more booleans into the
> > "struct device") so we can fully eliminate the need for the IOMMU
> > framework to reach into a PCIe device.
>
> It feels like the iommu code should not be messing with pci devices at
> all, please don't do this.
I think it's generally agreed that having the IOMMU code reach into
the PCIe code is pretty non-ideal, but that's not something that my
patch series added. The IOMMU code already has special cases to reach
into PCIe devices to decide strictness. I was actually trying to
reduce the amount of it.
> Why does this matter? Why wouldn't a pci device use "strict" iommu at
> all times? What happens if it does not? Why are PCI devices special?
This is something pre-existing in Linux. In my patch series I was
trying to make PCI devices less special and take some of the concepts
from there and expand them, but in a cleaner way. It sounds like in my
v2 I should steer away from this and leave the existing PCI hacks
alone.
-Doug
next prev parent reply other threads:[~2021-06-24 13:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 23:52 [PATCH 0/6] iommu: Enable devices to request non-strict DMA, starting with QCom SD/MMC Douglas Anderson
2021-06-21 23:52 ` [PATCH 1/6] drivers: base: Add the concept of "pre_probe" to drivers Douglas Anderson
2021-06-24 13:35 ` Greg KH
2021-06-21 23:52 ` [PATCH 2/6] drivers: base: Add bits to struct device to control iommu strictness Douglas Anderson
2021-06-24 13:36 ` Greg KH
2021-06-24 13:42 ` Doug Anderson
2021-06-21 23:52 ` [PATCH 3/6] PCI: Indicate that we want to force strict DMA for untrusted devices Douglas Anderson
2021-06-24 13:38 ` Greg KH
2021-06-24 13:46 ` Doug Anderson [this message]
2021-06-21 23:52 ` [PATCH 4/6] iommu: Combine device strictness requests with the global default Douglas Anderson
2021-06-22 2:03 ` Lu Baolu
2021-06-22 16:53 ` Doug Anderson
2021-06-22 17:01 ` Doug Anderson
2021-06-22 2:55 ` Saravana Kannan
2021-06-22 16:40 ` Doug Anderson
2021-06-22 19:50 ` Saravana Kannan
2021-06-22 11:49 ` Robin Murphy
2021-06-22 18:45 ` Rajat Jain
2021-06-22 19:35 ` Doug Anderson
2021-06-21 23:52 ` [PATCH 5/6] iommu: Stop reaching into PCIe devices to decide strict vs. non-strict Douglas Anderson
2021-06-21 23:52 ` [PATCH 6/6] mmc: sdhci-msm: Request non-strict IOMMU mode Douglas Anderson
2021-06-24 13:43 ` Greg KH
2021-06-24 14:00 ` Doug Anderson
2021-06-22 11:35 ` [PATCH 0/6] iommu: Enable devices to request non-strict DMA, starting with QCom SD/MMC Robin Murphy
2021-06-22 16:06 ` Doug Anderson
2021-06-22 20:02 ` Rob Herring
2021-06-22 20:05 ` Saravana Kannan
2021-06-22 20:10 ` Doug Anderson
2021-06-23 13:54 ` Rob Herring
2021-06-22 22:10 ` Robin Murphy
2021-06-23 17:29 ` Doug Anderson
2021-06-24 17:23 ` Doug Anderson
2021-06-22 17:39 ` John Garry
2021-06-22 19:50 ` Doug Anderson
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