* Marc-André Lureau (marcandre.lur...@gmail.com) wrote:
> Hi
>
> On Thu, Mar 8, 2018 at 8:58 PM, Dr. David Alan Gilbert (git)
> <dgilb...@redhat.com> wrote:
> > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> >
> > Clear the area and turn off THP.
> > PROT_NONE the area until after we've userfault advised it
> > to catch any unexpected changes.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
>
> Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
>
>
> > ---
> > contrib/libvhost-user/libvhost-user.c | 46
> > +++++++++++++++++++++++++++++++----
> > 1 file changed, 41 insertions(+), 5 deletions(-)
> >
> > diff --git a/contrib/libvhost-user/libvhost-user.c
> > b/contrib/libvhost-user/libvhost-user.c
> > index e02e5d6f46..1b224af706 100644
> > --- a/contrib/libvhost-user/libvhost-user.c
> > +++ b/contrib/libvhost-user/libvhost-user.c
> > @@ -454,7 +454,7 @@ vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg
> > *vmsg)
> > int i;
> > VhostUserMemory *memory = &vmsg->payload.memory;
> > dev->nregions = memory->nregions;
> > - /* TODO: Postcopy specific code */
> > +
> > DPRINT("Nregions: %d\n", memory->nregions);
> > for (i = 0; i < dev->nregions; i++) {
> > void *mmap_addr;
> > @@ -478,9 +478,12 @@ vu_set_mem_table_exec_postcopy(VuDev *dev,
> > VhostUserMsg *vmsg)
> >
> > /* We don't use offset argument of mmap() since the
> > * mapped address has to be page aligned, and we use huge
> > - * pages. */
> > + * pages.
> > + * In postcopy we're using PROT_NONE here to catch anyone
> > + * accessing it before we userfault
> > + */
> > mmap_addr = mmap(0, dev_region->size + dev_region->mmap_offset,
> > - PROT_READ | PROT_WRITE, MAP_SHARED,
> > + PROT_NONE, MAP_SHARED,
> > vmsg->fds[i], 0);
> >
> > if (mmap_addr == MAP_FAILED) {
> > @@ -519,12 +522,38 @@ vu_set_mem_table_exec_postcopy(VuDev *dev,
> > VhostUserMsg *vmsg)
> > /* OK, now we can go and register the memory and generate faults */
> > for (i = 0; i < dev->nregions; i++) {
> > VuDevRegion *dev_region = &dev->regions[i];
> > + int ret;
> > #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?
> > + * Discard any mapping we have here; note I can't use MADV_REMOVE
> > + * or fallocate to make the hole since I don't want to lose
> > + * data that's already arrived in the shared process.
> > + * TODO: How to do hugepage
> > */
> > + ret = madvise((void *)dev_region->mmap_addr,
> > + dev_region->size + dev_region->mmap_offset,
> > + MADV_DONTNEED);
> > + if (ret) {
> > + fprintf(stderr,
> > + "%s: Failed to madvise(DONTNEED) region %d: %s\n",
> > + __func__, i, strerror(errno));
> > + }
> > + /* Turn off transparent hugepages so we dont get lose wakeups
> > + * in neighbouring pages.
> > + * TODO: Turn this backon later.
> > + */
> > + ret = madvise((void *)dev_region->mmap_addr,
> > + dev_region->size + dev_region->mmap_offset,
> > + MADV_NOHUGEPAGE);
> > + if (ret) {
> > + /* Note: This can happen legally on kernels that are configured
> > + * without madvise'able hugepages
> > + */
> > + fprintf(stderr,
> > + "%s: Failed to madvise(NOHUGEPAGE) region %d: %s\n",
> > + __func__, i, strerror(errno));
> > + }
> > 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;
> > @@ -546,6 +575,13 @@ vu_set_mem_table_exec_postcopy(VuDev *dev,
> > VhostUserMsg *vmsg)
> > }
> > DPRINT("%s: region %d: Registered userfault for %llx + %llx\n",
> > __func__, i, reg_struct.range.start, reg_struct.range.len);
> > + /* Now it's registered we can let the client at it */
> > + if (mprotect((void *)dev_region->mmap_addr,
> > + dev_region->size + dev_region->mmap_offset,
> > + PROT_READ | PROT_WRITE)) {
> > + vu_panic(dev, "failed to mprotect region %d for postcopy", i);
>
> You could also strerror(errno) here.
Done
> > + return false;
> > + }
> > /* TODO: Stash 'zero' support flags somewhere */
> > #endif
> > }
> > --
> > 2.14.3
> >
> >
>
>
>
> --
> Marc-André Lureau
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
