On Thu, Jul 11, 2024 at 10:55 AM Stefan Hajnoczi <stefa...@redhat.com>
wrote:
> On Fri, Jun 28, 2024 at 04:57:10PM +0200, Albert Esteve wrote:
> > Implement function handlers for memory read and write
> > operations.
> >
> > Signed-off-by: Albert Esteve <aest...@redhat.com>
> > ---
> > hw/virtio/vhost-user.c | 34 ++++++++++++++++++++++++++++++----
> > 1 file changed, 30 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index 18cacb2d68..79becbc87b 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -1884,16 +1884,42 @@ static int
> > vhost_user_backend_handle_mem_read(struct vhost_dev *dev,
> > VhostUserMemRWMsg *mem_rw)
> > {
> > - /* TODO */
> > - return -EPERM;
> > + ram_addr_t offset;
> > + int fd;
> > + MemoryRegion *mr;
> > +
> > + mr = vhost_user_get_mr_data(mem_rw->guest_address, &offset, &fd);
> > +
> > + if (!mr) {
> > + error_report("Failed to get memory region with address %"
> PRIx64,
> > + mem_rw->guest_address);
> > + return -EFAULT;
> > + }
> > +
> > + memcpy(mem_rw->data, memory_region_get_ram_ptr(mr) + offset,
> mem_rw->size);
>
> Don't try to write this from scratch. Use address_space_read/write(). It
> supports corner cases like crossing MemoryRegions.
>
I am having issues getting the address space from the vhost_dev struct to
feed
address_spave_read/write() function with the first parameter. But I found
mr->ops.
Would something like this perhaps be enough?
```
mr->ops->read_with_attrs(mr->opaque, mem_rw->guest_address,
&mem_rw->data, mem_rw->size,
MEMTXATTRS_UNSPECIFIED);
```
>
> > +
> > + return 0;
> > }
> >
> > static int
> > vhost_user_backend_handle_mem_write(struct vhost_dev *dev,
> > VhostUserMemRWMsg *mem_rw)
> > {
> > - /* TODO */
> > - return -EPERM;
> > + ram_addr_t offset;
> > + int fd;
> > + MemoryRegion *mr;
> > +
> > + mr = vhost_user_get_mr_data(mem_rw->guest_address, &offset, &fd);
> > +
> > + if (!mr) {
> > + error_report("Failed to get memory region with address %"
> PRIx64,
> > + mem_rw->guest_address);
> > + return -EFAULT;
> > + }
> > +
> > + memcpy(memory_region_get_ram_ptr(mr) + offset, mem_rw->data,
> mem_rw->size);
> > +
> > + return 0;
> > }
> >
> > static void close_backend_channel(struct vhost_user *u)
> > --
> > 2.45.2
> >
>
