Re: [PATCH rc v7 4/6] iommu: Fix nested pci_dev_reset_iommu_prepare/done()

[Baolu Lu <baolu.lu@linux.intel.com>]

On 4/19/26 07:41, Nicolin Chen wrote:
> Shuai found that cxl_reset_bus_function() calls pci_reset_bus_function()
> internally while both are calling pci_dev_reset_iommu_prepare/done().
> 
> As pci_dev_reset_iommu_prepare() doesn't support re-entry, the inner call
> will trigger a WARN_ON and return -EBUSY, resulting in failing the entire
> device reset.
> 
> On the other hand, removing the outer calls in the PCI callers is unsafe.
> As pointed out by Kevin, device-specific quirks like reset_hinic_vf_dev()
> execute custom firmware waits after their inner pcie_flr() completes. If
> the IOMMU protection relies solely on the inner reset, the IOMMU will be
> unblocked prematurely while the device is still resetting.
> 
> Instead, fix this by making pci_dev_reset_iommu_prepare/done() reentrant.
> 
> Introduce gdev->reset_depth to handle the re-entries on the same device.
> 
> Fixes: c279e83953d9 ("iommu: Introduce pci_dev_reset_iommu_prepare/done()")
> Cc:stable@vger.kernel.org
> Reported-by: Shuai Xue<xueshuai@linux.alibaba.com>
> Closes:https://lore.kernel.org/all/absKsk7qQOwzhpzv@Asurada-Nvidia/
> Suggested-by: Kevin Tian<kevin.tian@intel.com>
> Reviewed-by: Shuai Xue<xueshuai@linux.alibaba.com>
> Reviewed-by: Jason Gunthorpe<jgg@nvidia.com>
> Reviewed-by: Kevin Tian<kevin.tian@intel.com>
> Signed-off-by: Nicolin Chen<nicolinc@nvidia.com>
> ---
>   drivers/iommu/iommu.c | 19 +++++++++++++------
>   1 file changed, 13 insertions(+), 6 deletions(-)

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>