Messages in this thread | | | Date | Thu, 7 May 2020 16:03:34 -0600 | From | Alex Williamson <> | Subject | Re: [PATCH v2 2/3] vfio-pci: Fault mmaps to enable vma tracking |
| |
On Thu, 7 May 2020 17:47:44 -0400 Peter Xu <peterx@redhat.com> wrote:
> Hi, Alex, > > On Tue, May 05, 2020 at 03:54:53PM -0600, Alex Williamson wrote: > > +/* > > + * Zap mmaps on open so that we can fault them in on access and therefore > > + * our vma_list only tracks mappings accessed since last zap. > > + */ > > +static void vfio_pci_mmap_open(struct vm_area_struct *vma) > > +{ > > + zap_vma_ptes(vma, vma->vm_start, vma->vm_end - vma->vm_start); > > A pure question: is this only a safety-belt or it is required in some known > scenarios?
It's not required. I originally did this so that I'm not allocating a vma_list entry in a path where I can't return error, but as Jason suggested I could zap here only in the case that I do encounter that allocation fault. However I still like consolidating the vma_list handling to the vm_ops .fault and .close callbacks and potentially we reduce the zap latency by keeping the vma_list to actual users, which we'll get to eventually anyway in the VM case as memory BARs are sized and assigned addresses.
> In all cases: > > Reviewed-by: Peter Xu <peterx@redhat.com>
Thanks! Alex
| |