Re: [PATCH v12 4/5] drivers/perf: add DesignWare PCIe PMU driver

[Shuai Xue <xueshuai@linux.alibaba.com>]

在 2024/12/10 06:47, Bjorn Helgaas 写道:
> On Mon, Dec 09, 2024 at 03:40:16PM +0000, Will Deacon wrote:
>> On Fri, Dec 06, 2024 at 10:54:57AM -0600, Bjorn Helgaas wrote:
>>> On Fri, Dec 08, 2023 at 10:56:51AM +0800, Shuai Xue wrote:
>>>> This commit adds the PCIe Performance Monitoring Unit (PMU) driver support
>>>> for T-Head Yitian SoC chip. Yitian is based on the Synopsys PCI Express
>>>> Core controller IP which provides statistics feature. The PMU is a PCIe
>>>> configuration space register block provided by each PCIe Root Port in a
>>>> Vendor-Specific Extended Capability named RAS D.E.S (Debug, Error
>>>> injection, and Statistics).
>>>
>>>> +#define DWC_PCIE_VSEC_RAS_DES_ID		0x02
>>>
>>>> +static const struct dwc_pcie_vendor_id dwc_pcie_vendor_ids[] = {
>>>> +	{.vendor_id = PCI_VENDOR_ID_ALIBABA },
>>>> +	{} /* terminator */
>>>> +};
>>>
>>>> +static bool dwc_pcie_match_des_cap(struct pci_dev *pdev)
>>>> +{
>>>> +	const struct dwc_pcie_vendor_id *vid;
>>>> +	u16 vsec;
>>>> +	u32 val;
>>>> +
>>>> +	if (!pci_is_pcie(pdev) || !(pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT))
>>>> +		return false;
>>>> +
>>>> +	for (vid = dwc_pcie_vendor_ids; vid->vendor_id; vid++) {
>>>> +		vsec = pci_find_vsec_capability(pdev, vid->vendor_id,
>>>> +						DWC_PCIE_VSEC_RAS_DES_ID);
>>>
>>> This looks wrong to me, and it promotes a misunderstanding of how VSEC
>>> Capabilities work.  The VSEC ID is defined by the vendor, so we have
>>> to check both the Vendor ID and the VSEC ID before we know what this
>>> VSEC Capability is.
>>
>> Thanks for pointing this out! The code's been merged for a while now,
>> so we'll need to fix what we have rather than revert it, I think.
> 
> Yep, for sure.
> 
>> Any chance you could send a patch with those, please? I'm also not able
>> to test this stuff, but I'm sure Ilkka would help us out.
> 
> Posted at https://lore.kernel.org/linux-pci/20241209222938.3219364-1-helgaas@kernel.org
> 
> Bjorn

Hi, Bjorn and Will,

Thanks for pointing this out and fix it so quickly, I will also test this patch
on our platform later.

Best Regards,
Shuai