linux-kernel - Re: [PATCH v2] PCI: Declare quirk_huawei_pcie_sva() as pci_fixup

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Message-ID: <20250315184523.GA848225@bhelgaas>
Date: Sat, 15 Mar 2025 13:45:23 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Baolu Lu <baolu.lu@...ux.intel.com>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	iommu@...ts.linux.dev, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Declare quirk_huawei_pcie_sva() as
 pci_fixup_header

On Sat, Mar 15, 2025 at 10:13:19AM +0000, Zhangfei Gao wrote:
> The commit bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper
> probe path") changes the arm_smmu_probe_device() sequence.

> The arm_smmu_probe_device() is now called earlier via pci_device_add(),
> which calls pci_fixup_device() at the "pci_fixup_header" phase, while
> originally it was called from the pci_bus_add_device(), which called
> pci_fixup_device() at the "pci_fixup_final" phase.
> 
> The callstack before:
> [ 1121.314405]  arm_smmu_probe_device+0x48/0x450
> [ 1121.314410]  __iommu_probe_device+0xc4/0x3c8
> [ 1121.314412]  iommu_probe_device+0x40/0x90
> [ 1121.314414]  acpi_dma_configure_id+0xb4/0x100
> [ 1121.314417]  pci_dma_configure+0xf8/0x108
> [ 1121.314421]  really_probe+0x78/0x278
> [ 1121.314425]  __driver_probe_device+0x80/0x140
> [ 1121.314427]  driver_probe_device+0x48/0x130
> [ 1121.314430]  __device_attach_driver+0xc0/0x108
> [ 1121.314432]  bus_for_each_drv+0x8c/0xf8
> [ 1121.314435]  __device_attach+0x104/0x1a0
> [ 1121.314437]  device_attach+0x1c/0x30
> [ 1121.314440]  pci_bus_add_device+0xb8/0x1f0
> [ 1121.314442]  pci_iov_add_virtfn+0x2ac/0x300
> 
> And after:
> [  215.072859]  arm_smmu_probe_device+0x48/0x450
> [  215.072871]  __iommu_probe_device+0xc0/0x468
> [  215.072875]  iommu_probe_device+0x40/0x90
> [  215.072877]  iommu_bus_notifier+0x38/0x68
> [  215.072879]  notifier_call_chain+0x80/0x148
> [  215.072886]  blocking_notifier_call_chain+0x50/0x80
> [  215.072889]  bus_notify+0x44/0x68
> [  215.072896]  device_add+0x580/0x768
> [  215.072898]  pci_device_add+0x1e8/0x568
> [  215.072906]  pci_iov_add_virtfn+0x198/0x300

The stacktraces definitely help connect the dots but don't integrate
the fixup phases and the timestamps are unnecessary distraction.

I would omit all the above except the first paragraph and include
something like this instead, which shows how arm_smmu_probe_device()
was previously after final fixups and is now between header and final
fixups:

  pci_iov_add_virtfn
    pci_device_add
      pci_fixup_device(pci_fixup_header)      <--
      device_add
        bus_notify
          iommu_bus_notifier
  +         iommu_probe_device
  +           arm_smmu_probe_device
    pci_bus_add_device
      pci_fixup_device(pci_fixup_final)       <--
      device_attach
        driver_probe_device
          really_probe
            pci_dma_configure
              acpi_dma_configure_id
  -             iommu_probe_device
  -               arm_smmu_probe_device

This is the pci_iov_add_virtfn().  The non-SR-IOV case is similar in
that pci_device_add() is called from pci_scan_single_device() in the
generic enumeration path, and pci_bus_add_device() is called later,
after all a host bridge has been enumerated.

> Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path")
> Signed-off-by: Zhangfei Gao <zhangfei.gao@...aro.org>
> [kwilczynski: commit log]
> Signed-off-by: Krzysztof Wilczyński <kwilczynski@...nel.org>

You should never include somebody else's Signed-off-by below yours.
You should only add *your own* Signed-off-by:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?id=v6.13#n396

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
> 
> v2: Modify commit log
> 
>  drivers/pci/quirks.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index f840d611c450..a9759889ff5e 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1991,12 +1991,12 @@ static void quirk_huawei_pcie_sva(struct pci_dev *pdev)
>  	    device_create_managed_software_node(&pdev->dev, properties, NULL))
>  		pci_warn(pdev, "could not add stall property");
>  }
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa250, quirk_huawei_pcie_sva);
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa251, quirk_huawei_pcie_sva);
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa255, quirk_huawei_pcie_sva);
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa256, quirk_huawei_pcie_sva);
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa258, quirk_huawei_pcie_sva);
> -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa259, quirk_huawei_pcie_sva);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, 0xa250, quirk_huawei_pcie_sva);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, 0xa251, quirk_huawei_pcie_sva);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, 0xa255, quirk_huawei_pcie_sva);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, 0xa256, quirk_huawei_pcie_sva);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, 0xa258, quirk_huawei_pcie_sva);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_HUAWEI, 0xa259, quirk_huawei_pcie_sva);
>  
>  /*
>   * It's possible for the MSI to get corrupted if SHPC and ACPI are used
> -- 
> 2.25.1
>