On Wed, 23 Aug 2023 12:16:23 -0300
Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> On Wed, Aug 23, 2023 at 09:14:07AM -0600, Alex Williamson wrote:
> > On Wed, 23 Aug 2023 14:50:31 +0000
> > Ankit Agrawal <ankita@xxxxxxxxxx> wrote:
> >
> > > >> + if (index == VFIO_PCI_BAR2_REGION_INDEX) {
> > > >> + if (!nvdev->opregion) {
> > > >> + nvdev->opregion = memremap(nvdev->hpa, nvdev->mem_length, MEMREMAP_WB);
> > > >> + if (!nvdev->opregion)
> > > >> + return -ENOMEM;
> > > >> + }
> > > >
> > > > [AW] Seems like this would be susceptible to concurrent accesses causing
> > > > duplicate mappings.
> > > >
> > > > [JG] Needs some kind of locking on opregion
> > >
> > > Right, will add a new lock item in nvdev to control the access to opregion/memmap.
> > > Please let me know if it is preferable to do memremap in open_device instead of
> > > read/write.
> >
> > That's a valid option also, certainly avoids the locking and
> > serialization per access. Thanks,
>
> open_device is no good, that would waste large amounts of kernel
> memory for page tables to support something we don't expect to be
> used.
A lock it is then, I guess this is a very large range of memory. The
contention/serialization is also not a priority, we expect access
through the mmap for anything other than debug. Thanks,
Alex
