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Re: [Qemu-devel] [RFC 16/29] vhost+postcopy: Stash RAMBlock and offset
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [RFC 16/29] vhost+postcopy: Stash RAMBlock and offset |
Date: |
Mon, 17 Jul 2017 10:59:44 +0800 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Fri, Jul 14, 2017 at 06:15:54PM +0100, Dr. David Alan Gilbert wrote:
> * Peter Xu (address@hidden) wrote:
> > On Wed, Jun 28, 2017 at 08:00:34PM +0100, Dr. David Alan Gilbert (git)
> > wrote:
> > > From: "Dr. David Alan Gilbert" <address@hidden>
> > >
> > > Stash the RAMBlock and offset for later use looking up
> > > addresses.
> > >
> > > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > > ---
> > > hw/virtio/trace-events | 1 +
> > > hw/virtio/vhost-user.c | 11 +++++++++++
> > > 2 files changed, 12 insertions(+)
> > >
> > > diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> > > index f7be340a45..1fd194363a 100644
> > > --- a/hw/virtio/trace-events
> > > +++ b/hw/virtio/trace-events
> > > @@ -3,6 +3,7 @@
> > > # hw/virtio/vhost-user.c
> > > vhost_user_postcopy_listen(void) ""
> > > vhost_user_set_mem_table_postcopy(uint64_t client_addr, uint64_t qhva,
> > > int reply_i, int region_i) "client:%"PRIx64" for hva: %"PRIx64" reply %d
> > > region %d"
> > > +vhost_user_set_mem_table_withfd(int index, const char *name, uint64_t
> > > memory_size, uint64_t guest_phys_addr, uint64_t userspace_addr, uint64_t
> > > offset) "%d:%s: size:%"PRIx64" GPA:%"PRIx64" QVA/userspace:%"PRIx64" RB
> > > offset:%"PRIx64
> > >
> > > # hw/virtio/virtio.c
> > > virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned
> > > out_num) "elem %p size %zd in_num %u out_num %u"
> > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > > index 6be3e7ff2d..3185af7a45 100644
> > > --- a/hw/virtio/vhost-user.c
> > > +++ b/hw/virtio/vhost-user.c
> > > @@ -133,6 +133,11 @@ struct vhost_user {
> > > NotifierWithReturn postcopy_notifier;
> > > struct PostCopyFD postcopy_fd;
> > > uint64_t postcopy_client_bases[VHOST_MEMORY_MAX_NREGIONS];
> > > + RAMBlock *region_rb[VHOST_MEMORY_MAX_NREGIONS];
> > > + /* The offset from the start of the RAMBlock to the start of the
> > > + * vhost region.
> > > + */
> > > + ram_addr_t region_rb_offset[VHOST_MEMORY_MAX_NREGIONS];
> >
> > Here the array size is VHOST_MEMORY_MAX_NREGIONS, while...
> >
> > > };
> > >
> > > static bool ioeventfd_enabled(void)
> > > @@ -324,8 +329,14 @@ static int vhost_user_set_mem_table(struct vhost_dev
> > > *dev,
> > > assert((uintptr_t)reg->userspace_addr == reg->userspace_addr);
> > > mr = memory_region_from_host((void
> > > *)(uintptr_t)reg->userspace_addr,
> > > &offset);
> > > + u->region_rb_offset[i] = offset;
> > > + u->region_rb[i] = mr->ram_block;
> >
> > ... can i>=VHOST_MEMORY_MAX_NREGIONS here? Or do we only need to note
> > this down if fd > 0 below? Thanks,
>
> I don't *think* so - I mean:
> for (i = 0; i < dev->mem->nregions; ++i) {
>
> so if that's the maximum number of regions and that's the number of
> regions we should be safe???
That's my concern - looks like dev->mem->nregions can be bigger than
that? At least I didn't really see a restriction on its size. The size
is changed in following stack:
vhost_region_add
vhost_set_memory
vhost_dev_assign_memory
And it's dynamic extended, without checks.
Indeed in the function vhost_user_set_mem_table() we have:
int fds[VHOST_MEMORY_MAX_NREGIONS];
But we are safe iiuc because we also have assertions to protect:
assert(fd_num < VHOST_MEMORY_MAX_NREGIONS);
fds[fd_num++] = fd;
Do we at least need that assert?
Thanks,
--
Peter Xu