From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Magnus Damm <magnus.damm@gmail.com>,
linux-arm-msm@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
Will Deacon <will.deacon@arm.com>,
okaya@codeaurora.org,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
iommu@lists.linux-foundation.org,
Geert Uytterhoeven <geert@linux-m68k.org>,
Hanjun Guo <hanjun.guo@linaro.org>,
linux-pci <linux-pci@vger.kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
tn@semihalf.com, sricharan@codeaurora.org,
linux-arm-msm-owner@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error
Date: Tue, 16 May 2017 17:10:04 +0300 [thread overview]
Message-ID: <1825810.fLbCv8umR7@avalon> (raw)
In-Reply-To: <5724f819-40db-e830-1ec1-62c887ba39ee@arm.com>
Hi Robin,
On Tuesday 16 May 2017 15:04:55 Robin Murphy wrote:
> On 16/05/17 08:17, Laurent Pinchart wrote:
> > On Tuesday 16 May 2017 07:53:57 sricharan@codeaurora.org wrote:
[snip]
> >> arch_teardown_dma_ops() being the inverse of arch_setup_dma_ops()
> >> ,dma_ops should be cleared in the teardown path. Otherwise
> >> this causes problem when the probe of device is retried after
> >> being deferred. The device's iommu structures are cleared
> >> after EPROBEDEFER error, but on the next try dma_ops will still
> >> be set to old value, which is not right.
> >>
> >> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> >> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> >> ---
> >>
> >> arch/arm/mm/dma-mapping.c | 1 +
> >> 1 file changed, 1 insertion(+)
> >>
> >> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> >> index ab4f745..a40f03e 100644
> >> --- a/arch/arm/mm/dma-mapping.c
> >> +++ b/arch/arm/mm/dma-mapping.c
> >> @@ -2358,6 +2358,7 @@ static void arm_teardown_iommu_dma_ops(struct
> >> device *dev)
> >
> >> __arm_iommu_detach_device(dev);
> >> arm_iommu_release_mapping(mapping);
> >> + set_dma_ops(dev, NULL);
> >> }
> >> #else
> >
> > The subject mentions arch_teardown_dma_ops(), which I think is correct,
> > but the patch adds the set_dma_ops() call to arm_teardown_iommu_dma_ops().
> >
> > However, the situation is perhaps more complex. Note the check at the
> > beginning of arch_setup_dma_ops():
> > /*
> > * Don't override the dma_ops if they have already been set. Ideally
> > * this should be the only location where dma_ops are set, remove this
> > * check when all other callers of set_dma_ops will have disappeared.
> > */
> > if (dev->dma_ops)
> > return;
> >
> > If you set the dma_ops to NULL in arm_teardown_iommu_dma_ops() or
> > arch_teardown_dma_ops(), the next call to arch_setup_dma_ops() will
> > override them. To be safe you should only set them to NULL if they have
> > been set by arch_setup_dma_ops(). More than that, arch_teardown_dma_ops()
> > should probably not call arm_teardown_iommu_dma_ops() at all if the
> > dma_ops were set by arm_iommu_attach_device() and not
> > arch_teardown_dma_ops().
>
> Under what circumstances is that an issue? We'll only be tearing down
> the DMA ops when unbinding the driver,
Or when deferring probe.
> and I think it would be erroneous to expect the device to retain much state
> after that. Everything else would be set up from scratch again if it get
> reprobed later, so why not the DMA ops?
Because the DMA ops might have been set elsewhere than arch_setup_dma_ops().
If you look at the patch that added the above warning, its commit message
states
commit 26b37b946a5c2658dbc37dd5d6df40aaa9685d70 (iommu-joerg/arm/core)
Author: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Date: Fri May 15 02:00:02 2015 +0300
arm: dma-mapping: Don't override dma_ops in arch_setup_dma_ops()
The arch_setup_dma_ops() function is in charge of setting dma_ops with a
call to set_dma_ops(). set_dma_ops() is also called from
- highbank and mvebu bus notifiers
- dmabounce (to be replaced with swiotlb)
- arm_iommu_attach_device
(arm_iommu_attach_device is itself called from IOMMU and bus master
device drivers)
To allow the arch_setup_dma_ops() call to be moved from device add time
to device probe time we must ensure that dma_ops already setup by any of
the above callers will not be overriden.
Aftering replacing dmabounce with swiotlb, converting IOMMU drivers to
of_xlate and taking care of highbank and mvebu, the workaround should be
removed.
I'm concerned about potentially breaking these if we unconditionally remove
the DMA ops and mapping.
--
Regards,
Laurent Pinchart
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2017-05-16 14:10 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-03 15:48 [PATCH V8 00/11] IOMMU probe deferral support Sricharan R
2017-02-03 15:48 ` [PATCH V8 01/11] iommu/of: Refactor of_iommu_configure() for error handling Sricharan R
2017-03-08 18:58 ` Jean-Philippe Brucker
2017-03-08 19:28 ` Robin Murphy
2017-03-09 9:52 ` sricharan
2017-03-09 11:21 ` Robin Murphy
2017-02-03 15:48 ` [PATCH V8 02/11] iommu/of: Prepare for deferred IOMMU configuration Sricharan R
2017-02-03 15:48 ` [PATCH V8 03/11] of: dma: Move range size workaround to of_dma_get_range() Sricharan R
2017-02-03 15:48 ` [PATCH V8 04/11] of: dma: Make of_dma_deconfigure() public Sricharan R
2017-02-03 15:48 ` [PATCH V8 05/11] ACPI/IORT: Add function to check SMMUs drivers presence Sricharan R
2017-02-03 15:48 ` [PATCH V8 06/11] of/acpi: Configure dma operations at probe time for platform/amba/pci bus devices Sricharan R
2017-02-03 15:48 ` [PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error Sricharan R
2017-05-02 18:35 ` Geert Uytterhoeven
2017-05-03 9:54 ` Robin Murphy
2017-05-03 10:24 ` Sricharan R
2017-05-03 11:13 ` Sricharan R
2017-05-05 13:23 ` Geert Uytterhoeven
2017-05-17 9:22 ` Magnus Damm
2017-05-17 10:28 ` Sricharan R
2017-05-15 14:22 ` Will Deacon
2017-05-16 2:26 ` sricharan
2017-05-15 20:37 ` Laurent Pinchart
2017-05-15 21:34 ` Laurent Pinchart
2017-05-16 2:23 ` sricharan
2017-05-16 7:17 ` Laurent Pinchart
2017-05-16 9:47 ` Sakari Ailus
2017-05-16 13:40 ` sricharan
2017-05-16 14:06 ` Laurent Pinchart
2017-05-16 14:04 ` Robin Murphy
2017-05-16 14:10 ` Laurent Pinchart [this message]
2017-05-16 14:29 ` sricharan
2017-05-16 14:46 ` Laurent Pinchart
2017-05-16 14:52 ` Robin Murphy
2017-02-03 15:48 ` [PATCH V8 08/11] drivers: acpi: " Sricharan R
2017-02-03 16:15 ` Sricharan
2017-02-03 17:39 ` Robin Murphy
2017-02-05 6:51 ` Sricharan
2017-02-03 15:48 ` [PATCH V8 09/11] arm64: dma-mapping: Remove the notifier trick to handle early setting of dma_ops Sricharan R
2017-02-03 15:48 ` [PATCH V8 10/11] iommu/arm-smmu: Clean up early-probing workarounds Sricharan R
2017-02-03 15:48 ` [PATCH V8 11/11] ACPI/IORT: Remove linker section for IORT entries probing Sricharan R
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=1825810.fLbCv8umR7@avalon \
--to=laurent.pinchart@ideasonboard.com \
--cc=bhelgaas@google.com \
--cc=geert@linux-m68k.org \
--cc=hanjun.guo@linaro.org \
--cc=iommu@lists.linux-foundation.org \
--cc=joro@8bytes.org \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-arm-msm-owner@vger.kernel.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=lorenzo.pieralisi@arm.com \
--cc=m.szyprowski@samsung.com \
--cc=magnus.damm@gmail.com \
--cc=okaya@codeaurora.org \
--cc=robin.murphy@arm.com \
--cc=sricharan@codeaurora.org \
--cc=tn@semihalf.com \
--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).