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From: Greg KH <gregkh@linuxfoundation.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: rafael@kernel.org, rafael.j.wysocki@intel.com, will@kernel.org,
	robin.murphy@arm.com, joro@8bytes.org,
	bjorn.andersson@linaro.org, ulf.hansson@linaro.org,
	adrian.hunter@intel.com, bhelgaas@google.com,
	robdclark@chromium.org, linux-arm-msm@vger.kernel.org,
	linux-pci@vger.kernel.org, quic_c_gdjako@quicinc.com,
	iommu@lists.linux-foundation.org, sonnyrao@chromium.org,
	saiprakash.ranjan@codeaurora.org, linux-mmc@vger.kernel.org,
	vbadigan@codeaurora.org, rajatja@google.com,
	saravanak@google.com, joel@joelfernandes.org,
	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 15:38:18 +0200	[thread overview]
Message-ID: <YNSKyu/a8S3Qywbc@kroah.com> (raw)
In-Reply-To: <20210621165230.3.I7accc008905590bb2b46f40f91a4aeda5b378007@changeid>

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.

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?

greg k-h

WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: ulf.hansson@linaro.org, rafael@kernel.org,
	linux-pci@vger.kernel.org, joel@joelfernandes.org,
	rajatja@google.com, will@kernel.org, robdclark@chromium.org,
	saravanak@google.com, rafael.j.wysocki@intel.com,
	quic_c_gdjako@quicinc.com, vbadigan@codeaurora.org,
	linux-arm-msm@vger.kernel.org, bhelgaas@google.com,
	sonnyrao@chromium.org, linux-mmc@vger.kernel.org,
	adrian.hunter@intel.com, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, robin.murphy@arm.com
Subject: Re: [PATCH 3/6] PCI: Indicate that we want to force strict DMA for untrusted devices
Date: Thu, 24 Jun 2021 15:38:18 +0200	[thread overview]
Message-ID: <YNSKyu/a8S3Qywbc@kroah.com> (raw)
In-Reply-To: <20210621165230.3.I7accc008905590bb2b46f40f91a4aeda5b378007@changeid>

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.

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?

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

  reply	other threads:[~2021-06-24 13:38 UTC|newest]

Thread overview: 68+ 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 ` Douglas Anderson
2021-06-21 23:52 ` [PATCH 1/6] drivers: base: Add the concept of "pre_probe" to drivers Douglas Anderson
2021-06-21 23:52   ` Douglas Anderson
2021-06-24 13:35   ` Greg KH
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
2021-06-21 23:52   ` Douglas Anderson
2021-06-24 13:36   ` Greg KH
2021-06-24 13:36     ` Greg KH
2021-06-24 13:42     ` Doug Anderson
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
2021-06-21 23:52   ` Douglas Anderson
2021-06-24 13:38   ` Greg KH [this message]
2021-06-24 13:38     ` Greg KH
2021-06-24 13:46     ` Doug Anderson
2021-06-24 13:46       ` Doug Anderson
2021-06-21 23:52 ` [PATCH 4/6] iommu: Combine device strictness requests with the global default Douglas Anderson
2021-06-21 23:52   ` Douglas Anderson
2021-06-22  2:03   ` Lu Baolu
2021-06-22  2:03     ` Lu Baolu
2021-06-22 16:53     ` Doug Anderson
2021-06-22 16:53       ` Doug Anderson
2021-06-22 17:01       ` Doug Anderson
2021-06-22 17:01         ` Doug Anderson
2021-06-22  2:55   ` Saravana Kannan
2021-06-22  2:55     ` Saravana Kannan via iommu
2021-06-22 16:40     ` Doug Anderson
2021-06-22 16:40       ` Doug Anderson
2021-06-22 19:50       ` Saravana Kannan
2021-06-22 19:50         ` Saravana Kannan via iommu
2021-06-22 11:49   ` Robin Murphy
2021-06-22 11:49     ` Robin Murphy
2021-06-22 18:45   ` Rajat Jain
2021-06-22 18:45     ` Rajat Jain via iommu
2021-06-22 19:35     ` Doug Anderson
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   ` Douglas Anderson
2021-06-21 23:52 ` [PATCH 6/6] mmc: sdhci-msm: Request non-strict IOMMU mode Douglas Anderson
2021-06-21 23:52   ` Douglas Anderson
2021-06-24 13:43   ` Greg KH
2021-06-24 13:43     ` Greg KH
2021-06-24 14:00     ` Doug Anderson
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 11:35   ` Robin Murphy
2021-06-22 16:06   ` Doug Anderson
2021-06-22 16:06     ` Doug Anderson
2021-06-22 20:02     ` Rob Herring
2021-06-22 20:02       ` Rob Herring
2021-06-22 20:05       ` Saravana Kannan
2021-06-22 20:05         ` Saravana Kannan via iommu
2021-06-22 20:10         ` Doug Anderson
2021-06-22 20:10           ` Doug Anderson
2021-06-23 13:54           ` Rob Herring
2021-06-23 13:54             ` Rob Herring
2021-06-22 22:10     ` Robin Murphy
2021-06-22 22:10       ` Robin Murphy
2021-06-23 17:29       ` Doug Anderson
2021-06-23 17:29         ` Doug Anderson
2021-06-24 17:23         ` Doug Anderson
2021-06-24 17:23           ` Doug Anderson
2021-06-22 17:39 ` John Garry
2021-06-22 17:39   ` John Garry
2021-06-22 19:50   ` Doug Anderson
2021-06-22 19:50     ` Doug Anderson

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