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SubjectRe: [PATCH] PCI: export pci device assignment info as read only via sysfs


----- Original Message -----
> This patch exports assignment flag of PCI device via sysfs, so user
> space application could know if PCI device was assigned to guest OS
> or not via interface as following from viewpoint of host device
> management:
>
> PCI device was assigned to guest OS
> $cat /sys/devices/pci0000:00/0000:00:1f.3/assigned
> 1
>
> PCI device isn't assigned to guest OS
> $cat /sys/devices/pci0000:00/0000:00:1f.3/assigned
> 0
>
> Compiled and tested with v3.18.1
>
> Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
> ---
> drivers/pci/pci-sysfs.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 2c6643f..0ac3780 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -547,6 +547,15 @@ static ssize_t driver_override_show(struct device *dev,
> }
> static DEVICE_ATTR_RW(driver_override);
>
> +static ssize_t assigned_show(struct device *dev, struct device_attribute
> *attr,
> + char *buf)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> +
> + return sprintf(buf, "%d\n", pci_is_dev_assigned(pdev) ? 1 : 0);
> +}
> +static DEVICE_ATTR_RO(assigned);
> +
> static struct attribute *pci_dev_attrs[] = {
> &dev_attr_resource.attr,
> &dev_attr_vendor.attr,
> @@ -573,6 +582,7 @@ static struct attribute *pci_dev_attrs[] = {
> &dev_attr_devspec.attr,
> #endif
> &dev_attr_driver_override.attr,
> + &dev_attr_assigned.attr,
> NULL,
> };
>

NAK. The assigned attribute of a device is already in contention, it's racy and not universally used. If we can't even make it a consistent and reliable internal interface, we certainly shouldn't be exposing it to userspace. Thanks,

Alex


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