Re: [PATCH 3/7] vfio/pci: Use vfio_device_unmap_mapping_range()

Alex Williamson
2021-08-10T21:51:04Z

On Tue, 10 Aug 2021 13:55:00 +0100
Christoph Hellwig <hch@infradead.org> wrote:

> On Tue, Aug 10, 2021 at 08:57:22AM -0300, Jason Gunthorpe wrote:
> > I'm not sure there is a real performance win to chase here? Doesn't
> > this only protect mmap against reset? The mmap isn't performance
> > sensitive, right?
> >
> > If this really needs extra optimization adding a rwsem to the devset
> > and using that across the whole set would surely be sufficient.
>
> Every mmio read or write takes memory_lock.

Exactly. Ideally we're not using that path often, but I don't think
that's a good excuse to introduce memory access serialization, or even
dependencies between devices. Thanks,

Alex