Re: [PATCH v6 01/17] PCI: Don't suspend IOMMU when probing reset capability

[sashiko-bot@kernel.org]

> reset_method_store() in drivers/pci/pci-sysfs.c discovers supported reset
> methods by calling reset_fn(pdev, PCI_RESET_PROBE, ...) without holding a
> device_lock, since the probe path is expected to query the device's reset
> capability without changing device state.
> 
> However, pci_reset_bus_function() and __pci_dev_specific_reset() violate
> that contract after pci_dev_reset_iommu_prepare/done() were added, which
> moves the device into a blocking domain and abruptly aborts any in-flight
> DMA. Doing this for a probe -- a state-query call that does not even hold
> device_lock -- can cause driver timeouts and data loss on a DMAing device.
> 
> The peer reset helpers all handle this correctly: they short-circuit on a
> probe input before touching the IOMMU.
> 
> Skip pci_dev_reset_iommu_prepare()/_done() entirely when probe is set. The
> inner reset routines already implement their own probe semantics, and they
> perform the capability checks and return without changing device state.
> 
> Fixes: f5b16b802174 ("PCI: Suspend iommu function prior to resetting a device")
> Cc: stable@vger.kernel.org
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Assisted-by: LLM
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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