linux-kernel - Re: [PATCH RFC] pci: fix device presence detection for VFs

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Date:   Tue, 11 Oct 2022 17:01:29 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH RFC] pci: fix device presence detection for VFs

On Mon, Oct 10, 2022 at 01:12:20PM -0400, Michael S. Tsirkin wrote:
> virtio uses the same driver for VFs and PFs.  Accordingly,
> pci_device_is_present is used to detect device presence. This function
> isn't currently working properly for VFs since it attempts reading
> device and vendor ID. Result is device marked broken incorrectly.  As
> VFs are present if and only if PF is present, just return the value for
> that device.
> 
> Reported-by: gongwei <gongwei833x@...il.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> 
> ---
> 
> Warning - compile tested only. gongwei could you help test and report
> please?


Just got a report in private email that it was tested and works well.
Will repost as non-RFC now.


>  drivers/pci/pci.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 95bc329e74c0..ba29b8e2f3c1 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6462,6 +6462,9 @@ bool pci_device_is_present(struct pci_dev *pdev)
>  {
>  	u32 v;
>  
> +	if (pdev->is_virtfn)
> +		return pci_device_is_present(pdev->physfn);
> +
>  	if (pci_dev_is_disconnected(pdev))
>  		return false;
>  	return pci_bus_read_dev_vendor_id(pdev->bus, pdev->devfn, &v, 0);
> -- 
> MST