Re: [Qemu-devel] [RFC v2 22/32] vhost+postcopy: Add vhost waker

[Peter Xu <peterx@redhat.com>]

On Thu, Aug 24, 2017 at 08:27:20PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Register a waker function in vhost-user code to be notified when
> pages arrive or requests to previously mapped pages get requested.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  hw/virtio/trace-events |  3 +++
>  hw/virtio/vhost-user.c | 26 ++++++++++++++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index f7d4b831fe..adebf6dc6b 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -7,6 +7,9 @@ vhost_user_postcopy_fault_handler_found(int i, uint64_t region_offset, uint64_t
>  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:0x%"PRIx64" for hva: 0x%"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:0x%"PRIx64" GPA:0x%"PRIx64" QVA/userspace:0x%"PRIx64" RB offset:0x%"PRIx64
> +vhost_user_postcopy_waker(const char *rb, uint64_t rb_offset) "%s + 0x%"PRIx64
> +vhost_user_postcopy_waker_found(uint64_t client_addr) "0x%"PRIx64
> +vhost_user_postcopy_waker_nomatch(const char *rb, uint64_t rb_offset) "%s + 0x%"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 2897ff70b3..3bff33a1a6 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -847,6 +847,31 @@ static int vhost_user_postcopy_fault_handler(struct PostCopyFD *pcfd,
>      return -1;
>  }
>  
> +static int vhost_user_postcopy_waker(struct PostCopyFD *pcfd, RAMBlock *rb,
> +                                     uint64_t offset)
> +{
> +    struct vhost_dev *dev = pcfd->data;
> +    struct vhost_user *u = dev->opaque;
> +    int i;
> +
> +    trace_vhost_user_postcopy_waker(qemu_ram_get_idstr(rb), offset);
> +    /* Translate the offset into an address in the clients address space */
> +    for (i = 0; i < MIN(dev->mem->nregions, u->region_rb_len); i++) {
> +        if (u->region_rb[i] == rb &&
> +            offset >= u->region_rb_offset[i] &&
> +            offset < (u->region_rb_offset[i] +
> +                      dev->mem->regions[i].memory_size)) {

Just curious: checks against offset should only be for safety, right?
Is there valid case that even rb is correct but the offset gets out of
the range of that RAMBlock?

> +            uint64_t client_addr = (offset - u->region_rb_offset[i]) +
> +                                   u->postcopy_client_bases[i];
> +            trace_vhost_user_postcopy_waker_found(client_addr);
> +            return postcopy_wake_shared(pcfd, client_addr, rb);
> +        }
> +    }
> +
> +    trace_vhost_user_postcopy_waker_nomatch(qemu_ram_get_idstr(rb), offset);
> +    return 0;
> +}
> +
>  /*
>   * Called at the start of an inbound postcopy on reception of the
>   * 'advise' command.
> @@ -892,6 +917,7 @@ static int vhost_user_postcopy_advise(struct vhost_dev *dev, Error **errp)
>      u->postcopy_fd.fd = ufd;
>      u->postcopy_fd.data = dev;
>      u->postcopy_fd.handler = vhost_user_postcopy_fault_handler;
> +    u->postcopy_fd.waker = vhost_user_postcopy_waker;
>      u->postcopy_fd.idstr = "vhost-user"; /* Need to find unique name */
>      postcopy_register_shared_ufd(&u->postcopy_fd);
>      return 0;
> -- 
> 2.13.5
> 

-- 
Peter Xu