On Tue, 20 Mar 2018 04:36:48 +0200 "Michael S. Tsirkin" <m...@redhat.com> wrote:
> On Tue, Mar 20, 2018 at 02:01:07AM +0000, Zhoujian (jay) wrote: > > > > > > > -----Original Message----- > > > From: Michael S. Tsirkin [mailto:m...@redhat.com] > > > Sent: Saturday, March 17, 2018 2:20 AM > > > To: qemu-devel@nongnu.org > > > Cc: Zhoujian (jay) <jianjay.z...@huawei.com> > > > Subject: [PATCH] vhost-user: avoid misaligned access > > > > > > We can't pass a pointer to memory field directly since it's within a > > > packed > > > structure, so isn't aligned. > > > Pass a pointer on stack and copy. > > > > > > Fixes: 30c4cc7 ("vhost: used_memslots refactoring") > > > Cc: Jay Zhou <jianjay.z...@huawei.com> > > > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > > > --- > > > > > > I had to apply this to fix make check errors with clang. > > > Pls review, test and ack. > > > > > > Thanks! > > > > > > hw/virtio/vhost-user.c | 14 +++++++++++--- > > > 1 file changed, 11 insertions(+), 3 deletions(-) > > > > > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index > > > c12fdd9..a44ee7f 100644 > > > --- a/hw/virtio/vhost-user.c > > > +++ b/hw/virtio/vhost-user.c > > > @@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct > > > vhost_dev *dev, > > > bool reply_supported = virtio_has_feature(dev->protocol_features, > > > > > > VHOST_USER_PROTOCOL_F_REPLY_ACK); > > > VhostUserMsg msg_reply; > > > + VhostUserMemory memory = {}; > > > int region_i, msg_i; > > > > > > VhostUserMsg msg = { > > > @@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct > > > vhost_dev *dev, > > > msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > > > } > > > > > > - if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) { > > > + if (vhost_user_prepare_msg(dev, &memory, fds) < 0) { > > > error_report("Failed preparing vhost-user memory table msg"); > > > return -1; > > > } > > > + msg.payload.memory = memory; > > > > > > fd_num = msg.payload.memory.nregions; > > > > > > @@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev > > > *dev, > > > .hdr.request = VHOST_USER_SET_MEM_TABLE, > > > .hdr.flags = VHOST_USER_VERSION, > > > }; > > > + VhostUserMemory memory = {}; > > > > > > if (reply_supported) { > > > msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > > > } > > > > > > - if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) { > > > + if (vhost_user_prepare_msg(dev, &memory, fds) < 0) { > > > error_report("Failed preparing vhost-user memory table msg"); > > > return -1; > > > } > > > > > > + msg.payload.memory = memory; > > > + > > > fd_num = msg.payload.memory.nregions; > > > > > > if (!fd_num) { > > > @@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct > > > vhost_dev *dev) { > > > int fds[VHOST_MEMORY_MAX_NREGIONS]; > > > VhostUserMsg msg; > > > + VhostUserMemory memory = {}; > > > + > > > + vhost_user_prepare_msg(dev, &memory, fds); > > > > > > - vhost_user_prepare_msg(dev, &msg.payload.memory, fds); > > > + msg.payload.memory = memory; > > > } > > FYI I think it's better to pass pointer to msg to > avoid alignment issues. > > > Hi Michael, here should be like this: > > > > > > static void vhost_user_set_used_memslots(struct vhost_dev *dev) > > { > > int fds[VHOST_MEMORY_MAX_NREGIONS]; > > - VhostUserMsg msg; > > + VhostUserMemory memory = {}; > > > > - vhost_user_prepare_msg(dev, &msg.payload.memory, fds); > > + vhost_user_prepare_msg(dev, &memory, fds); > > } > > > > > > Regards, > > Jay > > > But what's the point of all this? The structure is discarded > after being initialized. Doesn't look right to me. I think it was my idea, point is to share vhost_user_prepare_msg() between _set_used_memslots and _set_mem_table* instead of duplicating code, of cause at the cost of discarding results in vhost_user_set_used_memslots() > > > > > > > const VhostOps user_ops = { > > > -- > > > MST >
