Messages in this thread | | | Subject | Re: [PATCH v3 09/14] iommu/arm-smmu: Prevent forced unbinding of Arm SMMU drivers | From | John Garry <> | Date | Wed, 27 Nov 2019 11:04:25 +0000 |
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On 26/11/2019 20:27, Saravana Kannan wrote: > On Tue, Nov 26, 2019 at 1:13 AM John Garry <john.garry@huawei.com> wrote: >> >> On 21/11/2019 11:49, Will Deacon wrote: >>> Forcefully unbinding the Arm SMMU drivers is a pretty dangerous operation, >>> since it will likely lead to catastrophic failure for any DMA devices >>> mastering through the SMMU being unbound. When the driver then attempts >>> to "handle" the fatal faults, it's very easy to trip over dead data >>> structures, leading to use-after-free. >>> >>> On John's machine, he reports that the machine was "unusable" due to >>> loss of the storage controller following a forced unbind of the SMMUv3 >>> driver: >>> >>> | # cd ./bus/platform/drivers/arm-smmu-v3 >>> | # echo arm-smmu-v3.0.auto > unbind >>> | hisi_sas_v2_hw HISI0162:01: CQE_AXI_W_ERR (0x800) found! >>> | platform arm-smmu-v3.0.auto: CMD_SYNC timeout at 0x00000146 >>> | [hwprod 0x00000146, hwcons 0x00000000] >>> >>> Prevent this forced unbinding of the drivers by setting "suppress_bind_attrs" >>> to true. >> >> This seems a reasonable approach for now. >> >> BTW, I'll give this series a spin this week, which again looks to be >> your iommu/module branch, excluding the new IORT patch. >
Hi Saravana,
> Is this on a platform where of_devlink creates device links between > the iommu device and its suppliers?I'm guessing no? Because device > links should for unbinding of all the consumers before unbinding the > supplier.
I'm only really interested in ACPI, TBH.
> > Looks like it'll still allow the supplier to unbind if the consumers > don't allow unbinding. Is that the case here?
So just unbinding the driver from a device does not delete the device nor exit the device from it's IOMMU group - so we keep the reference to the SMMU ko. As such, I don't know how to realistically test unloading the SMMU ko when we have platform devices involved. Maybe someone can enlighten me...
Thanks, John
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