On Mon, 30 Jun 2025 21:15:58 +0800
Yi Liu <yi.l.liu@xxxxxxxxx> wrote:
> On 2025/6/27 06:56, Alex Williamson wrote:
> > In the below noted Fixes commit we introduced a reflck mutex to allow
> > better scaling between devices for open and close. The reflck was
> > based on the hot reset granularity, device level for root bus devices
> > which cannot support hot reset or bus/slot reset otherwise. Overlooked
> > in this were SR-IOV VFs, where there's also no bus reset option, but
> > the default for a non-root-bus, non-slot-based device is bus level
> > reflck granularity.
> >
> > The reflck mutex has since become the dev_set mutex and is our defacto
> > serialization for various operations and ioctls. It still seems to be
> > the case though that sets of vfio-pci devices really only need
>
> a nit: not sure if mentioning 2cd8b14aaa66 which convers reflck to dev_set
> mutex is helpful. Perhaps, it's welcomed by people working on backporting. :)
Sure, I'll just insert a reference here on commit: "... has since become
the dev_set mutex (via commit 2cd8b14aaa66 ("vfio/pci: Move to the
device set infrastructure")) and is our defacto..."
> > serialization relative to hot resets affecting the entire set, which
> > is not relevant to SR-IOV VFs. As described in the Closes link below,
> > this serialization contributes to startup latency when multiple VFs
> > sharing the same "bus" are opened concurrently.
> >
> > Mark the device itself as the basis of the dev_set for SR-IOV VFs.
> >
> > Reported-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
> > Closes: https://lore.kernel.org/all/20250626180424.632628-1-aaronlewis@xxxxxxxxxx
> > Tested-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
> > Fixes: e309df5b0c9e ("vfio/pci: Parallelize device open and release")
> > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > ---
> > drivers/vfio/pci/vfio_pci_core.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Reviewed-by: Yi Liu <yi.l.liu@xxxxxxxxx>
Thanks,
Alex
