On (Thu) 17 Mar 2011 [15:26:28], Rusty Russell wrote: > On Wed, 16 Mar 2011 19:12:10 +0530, Amit Shah <amit.shah@xxxxxxxxxx> wrote: > > When detaching a buffer from a vq, the avail.idx value should be > > decremented as well. > > > > This was noticed by hot-unplugging a virtio console port and then > > plugging in a new one on the same number (re-using the vqs which were > > just 'disowned'). qemu reported > > > > 'Guest moved used index from 0 to 256' > > > > when any IO was attempted on the new port. > > Yech... detach_unused_buf cannot be used on a live virtqueue; it assumes > we will reset the vq (usually by resetting the entire device). > > You've partially violated that assumption by reusing the vq after > calling detach_unused_buf. So I'm not entirely sure this is the only > bug lurking; safer would be to re-initialize the vq somehow when you > plug back in... Right; and then that will need host changes too (re-init the vqs on the host side), which then gets us into compat problems... Amit _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
