On Thu, Mar 08, 2018 at 07:57:56PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <[email protected]>
>
> When new regions are sent to the client using SET_MEM_TABLE, register
> them with the userfaultfd.
>
> Signed-off-by: Dr. David Alan Gilbert <[email protected]>
> ---
> contrib/libvhost-user/libvhost-user.c | 34 ++++++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/contrib/libvhost-user/libvhost-user.c
> b/contrib/libvhost-user/libvhost-user.c
> index 4922b2c722..a18bc74a7c 100644
> --- a/contrib/libvhost-user/libvhost-user.c
> +++ b/contrib/libvhost-user/libvhost-user.c
> @@ -494,6 +494,40 @@ vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg
> *vmsg)
> close(vmsg->fds[i]);
> }
>
> + /* TODO: Get address back to QEMU */
> + for (i = 0; i < dev->nregions; i++) {
> + VuDevRegion *dev_region = &dev->regions[i];
> +#ifdef UFFDIO_REGISTER
> + /* We should already have an open ufd. Mark each memory
> + * range as ufd.
> + * Note: Do we need any madvises? Well it's not been accessed
> + * yet, still probably need no THP to be safe, discard to be safe?
> + */
> + struct uffdio_register reg_struct;
> + reg_struct.range.start = (uintptr_t)dev_region->mmap_addr;
> + reg_struct.range.len = dev_region->size + dev_region->mmap_offset;
Do we really care the page faults between offset zero to mmap_offset?
I'm thinking whether we should add that mmap_offset into range.start
instead of range.len.
Also, I see that in current vu_set_mem_table_exec():
/* We don't use offset argument of mmap() since the
* mapped address has to be page aligned, and we use huge
* pages. */
mmap_addr = mmap(0, dev_region->size + dev_region->mmap_offset,
PROT_READ | PROT_WRITE, MAP_SHARED,
vmsg->fds[i], 0);
So adding the mmap_offset will help to make sure we'll use huge pages?
Could it? Or say, how could we be sure that size+mmap_offset would be
page aligned?
Thanks,
> + reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
> +
> + if (ioctl(dev->postcopy_ufd, UFFDIO_REGISTER, ®_struct)) {
> + vu_panic(dev, "%s: Failed to userfault region %d "
> + "@%p + size:%zx offset: %zx: (ufd=%d)%s\n",
> + __func__, i,
> + dev_region->mmap_addr,
> + dev_region->size, dev_region->mmap_offset,
> + dev->postcopy_ufd, strerror(errno));
> + return false;
> + }
> + if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
> + vu_panic(dev, "%s Region (%d) doesn't support COPY",
> + __func__, i);
> + return false;
> + }
> + DPRINT("%s: region %d: Registered userfault for %llx + %llx\n",
> + __func__, i, reg_struct.range.start, reg_struct.range.len);
> + /* TODO: Stash 'zero' support flags somewhere */
> +#endif
> + }
> +
> return false;
> }
>
> --
> 2.14.3
>
--
Peter Xu
