linux-kernel - Re: [PATCH v2] PCI: Do not attempt to set ExtTag for VFs

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Message-ID: <99561464-1C66-4075-9963-C67F8C492E46@oracle.com>
Date: Tue, 2 Dec 2025 07:56:44 +0000
From: Haakon Bugge <haakon.bugge@...cle.com>
To: Bjorn Helgaas <bhelgaas@...gle.com>, Sinan Kaya <okaya@...eaurora.org>
CC: "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] PCI: Do not attempt to set ExtTag for VFs



> On 12 Nov 2025, at 10:54, Håkon Bugge <Haakon.Bugge@...cle.com> wrote:
> 
> The bit for enabling extended tags is Reserved and Preserved (RsvdP)
> for VFs, according to PCIe r7.0 section 7.5.3.4 table 7.21.  Hence,
> bail out early from pci_configure_extended_tags() if the device is a
> VF.
> 
> Otherwise, we may see incorrect log messages such as:
> 
>   kernel: pci 0000:af:00.2: enabling Extended Tags
> 
> (af:00.2 is a VF)
> 
> Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported")
> Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>

A gentle ping on this one.


Thxs, Håkon

> 
> ---
> 
> v1 -> v2: Added ref to PCIe spec
> ---
> drivers/pci/probe.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 0ce98e18b5a87..014017e15bcc8 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2244,7 +2244,8 @@ int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
> u16 ctl;
> int ret;
> 
> - if (!pci_is_pcie(dev))
> + /* PCI_EXP_DEVCTL_EXT_TAG is RsvdP in VFs */
> + if (!pci_is_pcie(dev) || dev->is_virtfn)
> return 0;
> 
> ret = pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
> -- 
> 2.43.5
>