linux/drivers/vhost, branch v3.2.38

vhost: fix mergeable bufs on BE hosts

2012-10-30T23:27:00Z

commit 910a578f7e9400a78a3b13aba0b4d2df16a2cb05 upstream. We copy head count to a 16 bit field, this works by chance on LE but on BE guest gets 0. Fix it up. Signed-off-by: Michael S. Tsirkin Tested-by: Alexander Graf Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings

vhost: don't forget to schedule()

2012-07-25T03:11:38Z

commit d550dda192c1bd039afb774b99485e88b70d7cb8 upstream. This is a tiny, but important, patch to vhost. Vhost's worker thread only called schedule() when it had no work to do, and it wanted to go to sleep. But if there's always work to do, e.g., the guest is running a network-intensive program like netperf with small message sizes, schedule() was *never* called. This had several negative implications (on non-preemptive kernels): 1. Passing time was not properly accounted to the "vhost" process (ps and top would wrongly show it using zero CPU time). 2. Sometimes error messages about RCU timeouts would be printed, if the core running the vhost thread didn't schedule() for a very long time. 3. Worst of all, a vhost thread would "hog" the core. If several vhost threads need to share the same core, typically one would get most of the CPU time (and its associated guest most of the performance), while the others hardly get any work done. The trivial solution is to add if (need_resched()) schedule(); After doing every piece of work. This will not do the heavy schedule() all the time, just when the timer interrupt decided a reschedule is warranted (so need_resched returns true). Thanks to Abel Gordon for this patch. Signed-off-by: Nadav Har'El Signed-off-by: Michael S. Tsirkin Signed-off-by: Ben Hutchings

atomic: use

2011-07-26T23:49:47Z

This allows us to move duplicated code in (atomic_inc_not_zero() for now) to Signed-off-by: Arun Sharma Reviewed-by: Eric Dumazet Cc: Ingo Molnar Cc: David Miller Cc: Eric Dumazet Acked-by: Mike Frysinger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

vhost: handle wrap around in # of bufs math

2011-07-21T07:48:27Z

The meth for calculating the # of outstanding buffers gives incorrect results when vq->upend_idx wraps around zero. Fix that. Signed-off-by: Shirley Ma Signed-off-by: Michael S. Tsirkin

vhost-net: update used ring on backend change

2011-07-21T07:23:31Z

On backend change, we flushed out outstanding skbs but forgot to update the used ring, so that done entries were left in the ubuf_info ring. As a result we lose heads or complete incorrect ones, crashing the guest or leaking memory. Fix by updating the used ring. Signed-off-by: Michael S. Tsirkin

vhost: optimize interrupt enable/disable

2011-07-19T14:17:28Z

As we now only update used ring after enabling the backend, we can write flags with __put_user: as that's done on data path, it matters. Signed-off-by: Michael S. Tsirkin

vhost: fix zcopy reference counting

2011-07-19T10:28:34Z

Fix get/put refcount imbalance with zero copy, which caused qemu to hang forever on guest driver unload. Signed-off-by: Michael S. Tsirkin

vhost: set log when updating used flags or avail event

2011-07-19T10:28:34Z

We need to log writes when updating used flags and avail event fields. Otherwise the guest may see a stale value after migration and miss notifying the host. Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin

vhost: init used ring after backend was set

2011-07-19T10:28:34Z

Move the used ring initialization after backend was set. This makes it possible to disable the backend and tweak the used ring, then restart. This will also make it possible to log the used ring write correctly. Signed-off-by: Jason Wang Signed-off-by: Michael S. Tsirkin

vhost: vhost TX zero-copy support

2011-07-18T17:42:32Z

>From: Shirley Ma This adds experimental zero copy support in vhost-net, disabled by default. To enable, set experimental_zcopytx module option to 1. This patch maintains the outstanding userspace buffers in the sequence it is delivered to vhost. The outstanding userspace buffers will be marked as done once the lower device buffers DMA has finished. This is monitored through last reference of kfree_skb callback. Two buffer indices are used for this purpose. The vhost-net device passes the userspace buffers info to lower device skb through message control. DMA done status check and guest notification are handled by handle_tx: in the worst case is all buffers in the vq are in pending/done status, so we need to notify guest to release DMA done buffers first before we get any new buffers from the vq. One known problem is that if the guest stops submitting buffers, buffers might never get used until some further action, e.g. device reset. This does not seem to affect linux guests. Signed-off-by: Shirley Signed-off-by: Michael S. Tsirkin Signed-off-by: David S. Miller