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

[Shuai Xue]

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@xxxxxxxxxx
>
> 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