linux-kernel - Re: [PATCH] PCI: Add device-specific reset for Kunpeng virtual functions

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Message-ID: <20250714191903.GA2414617@bhelgaas>
Date: Mon, 14 Jul 2025 14:19:03 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Weili Qian <qianweili@...wei.com>
Cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, liulongfang@...wei.com,
	Hui Wang <hui.wang@...onical.com>
Subject: Re: [PATCH] PCI: Add device-specific reset for Kunpeng virtual
 functions

[+cc Hui]

On Sat, Jul 12, 2025 at 07:30:28PM +0800, Weili Qian wrote:
> Prior to commit d591f6804e7e ("PCI: Wait for device readiness with
> Configuration RRS"), pci_dev_wait() polls PCI_COMMAND register until
> its value is not ~0(i.e., PCI_ERROR_RESPONSE). After d591f6804e7e,
> if the Configuration Request Retry Status Software Visibility (RRS SV)
> is enabled, pci_dev_wait() polls PCI_VENDOR_ID register until its value
> is not the reserved Vendor ID value 0x0001.
> 
> On Kunpeng accelerator devices, RRS SV is enabled. However,
> when the virtual function's FLR (Function Level Reset) is not
> ready, the pci_dev_wait() reads the PCI_VENDOR_ID register and gets
> the value 0xffff instead of 0x0001. It then incorrectly assumes this
> is a valid Vendor ID and concludes the device is ready, returning
> successfully. In reality, the function may not be fully ready, leading
> to the device becoming unavailable.
> 
> A 100ms wait period is already implemented before calling pci_dev_wait().
> In most cases, FLR completes within 100ms. However, to eliminate the
> risk of function being unavailable due to an incomplete FLR, a
> device-specific reset is added. After pcie_flr(), the function continues
> to poll PCI_COMMAND register until its value is no longer ~0.

As far as I can tell, there's nothing specific to Kungpeng devices
here.  We've seen a similar issue with Intel NVMe devices [1], and I
don't want a whole mess of quirks and device-specific reset methods.

We need some sort of generic solution for this.  My understanding was
that if devices are not ready 100ms after a reset, they are required
to respond with RRS.  Maybe these devices are defective.  Or maybe my
understanding is incorrect.  Either way, I think we should at least
check for a PCIe error before assuming that 0xffff is a valid
response.

[1] https://lore.kernel.org/linux-pci/20250611101442.387378-1-hui.wang@canonical.com/

> Fixes: d591f6804e7e ("PCI: Wait for device readiness with Configuration RRS")
> Signed-off-by: Weili Qian <qianweili@...wei.com>
> ---
>  drivers/pci/quirks.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index d7f4ee634263..1df1756257d2 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4205,6 +4205,36 @@ static int reset_hinic_vf_dev(struct pci_dev *pdev, bool probe)
>  	return 0;
>  }
>  
> +#define KUNPENG_OPERATION_WAIT_CNT	3000
> +#define KUNPENG_RESET_WAIT_TIME		20
> +
> +/* Device-specific reset method for Kunpeng accelerator virtual functions */
> +static int reset_kunpeng_acc_vf_dev(struct pci_dev *pdev, bool probe)
> +{
> +	u32 wait_cnt = 0;
> +	u32 cmd;
> +
> +	if (probe)
> +		return 0;
> +
> +	pcie_flr(pdev);
> +
> +	do {
> +		pci_read_config_dword(pdev, PCI_COMMAND, &cmd);
> +		if (!PCI_POSSIBLE_ERROR(cmd))
> +			break;
> +
> +		if (++wait_cnt > KUNPENG_OPERATION_WAIT_CNT) {
> +			pci_warn(pdev, "wait for FLR ready timeout; giving up\n");
> +			return -ENOTTY;
> +		}
> +
> +		msleep(KUNPENG_RESET_WAIT_TIME);
> +	} while (true);
> +
> +	return 0;
> +}
> +
>  static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
>  	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82599_SFP_VF,
>  		 reset_intel_82599_sfp_virtfn },
> @@ -4220,6 +4250,12 @@ static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
>  		reset_chelsio_generic_dev },
>  	{ PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HINIC_VF,
>  		reset_hinic_vf_dev },
> +	{ PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HUAWEI_ZIP_VF,
> +		reset_kunpeng_acc_vf_dev },
> +	{ PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HUAWEI_SEC_VF,
> +		reset_kunpeng_acc_vf_dev },
> +	{ PCI_VENDOR_ID_HUAWEI, PCI_DEVICE_ID_HUAWEI_HPRE_VF,
> +		reset_kunpeng_acc_vf_dev },
>  	{ 0 }
>  };
>  
> -- 
> 2.33.0
>