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>From 11fd997d724f520ca628615e7ffbfd7901c40b62 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp> Date: Fri, 6 Feb 2015 13:28:38 +0900 Subject: [PATCH] virtio: Avoid possible kernel panic if DEBUG is enabled. The virtqueue_add() calls START_USE() upon entry. The virtqueue_kick() is called if vq->num_added == (1 << 16) - 1 before calling END_USE(). The virtqueue_kick_prepare() called via virtqueue_kick() calls START_USE() upon entry, and will call panic() if DEBUG is enabled. Move this virtqueue_kick() call to after END_USE() cal...

>From 11fd997d724f520ca628615e7ffbfd7901c40b62 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp> Date: Fri, 6 Feb 2015 13:28:38 +0900 Subject: [PATCH] virtio: Avoid possible kernel panic if DEBUG is enabled. The virtqueue_add() calls START_USE() upon entry. The virtqueue_kick() is called if vq->num_added == (1 << 16) - 1 before calling END_USE(). The virtqueue_kick_prepare() called via virtqueue_kick() calls START_USE() upon entry, and will call panic() if DEBUG is enabled. Move this virtqueue_kick() call to after END_USE() cal...

...needs_kick; > } > @@ -1098,7 +1111,7 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > void **ctx) > { > struct vring_virtqueue *vq = to_vvq(_vq); > - u16 last_used, id; > + u16 wrap_counter, last_used, id; > void *ret; > > START_USE(vq); > @@ -1138,6 +1151,19 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > ret = vq->desc_state[id].data; > detach_buf_packed(vq, last_used, id, ctx); > > + wrap_counter = vq->wrap_counter; > + if (vq->last_used_idx > vq->next_avail_i...

...needs_kick; > } > @@ -1098,7 +1111,7 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > void **ctx) > { > struct vring_virtqueue *vq = to_vvq(_vq); > - u16 last_used, id; > + u16 wrap_counter, last_used, id; > void *ret; > > START_USE(vq); > @@ -1138,6 +1151,19 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > ret = vq->desc_state[id].data; > detach_buf_packed(vq, last_used, id, ctx); > > + wrap_counter = vq->wrap_counter; > + if (vq->last_used_idx > vq->next_avail_i...

Hello everyone, This RFC implements packed ring support in virtio driver. Some simple functional tests have been done with Jason's packed ring implementation in vhost: https://lkml.org/lkml/2018/4/23/12 Both of ping and netperf worked as expected (with EVENT_IDX disabled). TODO: - Refinements (for code and commit log); - More tests; - Bug fixes; RFC v3 -> RFC v4: - Make ID allocation

Hello everyone, This RFC implements packed ring support in virtio driver. Some simple functional tests have been done with Jason's packed ring implementation in vhost (RFC v4): https://lkml.org/lkml/2018/5/16/501 Both of ping and netperf worked as expected w/ EVENT_IDX disabled. Ping worked as expected w/ EVENT_IDX enabled, but netperf didn't (A hack has been added in the driver to

Hello everyone, This RFC implements packed ring support in virtio driver. Some simple functional tests have been done with Jason's packed ring implementation in vhost (RFC v4): https://lkml.org/lkml/2018/5/16/501 Both of ping and netperf worked as expected w/ EVENT_IDX disabled. Ping worked as expected w/ EVENT_IDX enabled, but netperf didn't (A hack has been added in the driver to

...ctx, gfp_t gfp) { + struct vring_virtqueue *vq = to_vvq(_vq); + struct vring_packed_desc *desc; + struct scatterlist *sg; + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx; + __virtio16 uninitialized_var(head_flags), flags; + int head, wrap_counter; + bool indirect; + + START_USE(vq); + + BUG_ON(data == NULL); + BUG_ON(ctx && vq->indirect); + + if (unlikely(vq->broken)) { + END_USE(vq); + return -EIO; + } + +#ifdef DEBUG + { + ktime_t now = ktime_get(); + + /* No kick or get, with .1 second between? Warn. */ + if (vq->last_add_time_valid) + WARN_ON...

...back is designed as an optimization to tell the host we don't need callbacks now. As it is not reliable, the debug check is overzealous: it can happen on two CPUs at the same time. Document this. Even if it were reliable, the virtio_net driver doesn't disable callbacks on transmit so the START_USE/END_USE debugging reentrance protection can be easily tripped even on UP. Thanks to Balaji Rao for the bug report and testing. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> CC: Balaji Rao <balajirrao at gmail.com> diff -r 0b3e64be7696 drivers/virtio/virtio_ring.c --- a/dri...

...back is designed as an optimization to tell the host we don't need callbacks now. As it is not reliable, the debug check is overzealous: it can happen on two CPUs at the same time. Document this. Even if it were reliable, the virtio_net driver doesn't disable callbacks on transmit so the START_USE/END_USE debugging reentrance protection can be easily tripped even on UP. Thanks to Balaji Rao for the bug report and testing. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> CC: Balaji Rao <balajirrao at gmail.com> diff -r 0b3e64be7696 drivers/virtio/virtio_ring.c --- a/dri...

...after napi_complete, so with NAPI_STATE_SCHED clear - outside the implicit napi lock. This violates the requirement to synchronize virtqueue_enable_cq wrt virtqueue_add_buf. In particular, used event can move backwards, causing us to lose interrupts. In a debug build, this can trigger panic within START_USE. Jason Wang reports that he can trigger the races artificially, by adding udelay() in virtqueue_enable_cb() after virtio_mb(). However, we must call napi_complete to clear NAPI_STATE_SCHED before polling the virtqueue for used buffers, otherwise napi_schedule_prep in a callback will fail, causin...

...after napi_complete, so with NAPI_STATE_SCHED clear - outside the implicit napi lock. This violates the requirement to synchronize virtqueue_enable_cq wrt virtqueue_add_buf. In particular, used event can move backwards, causing us to lose interrupts. In a debug build, this can trigger panic within START_USE. Jason Wang reports that he can trigger the races artificially, by adding udelay() in virtqueue_enable_cb() after virtio_mb(). However, we must call napi_complete to clear NAPI_STATE_SCHED before polling the virtqueue for used buffers, otherwise napi_schedule_prep in a callback will fail, causin...

...gfp_t gfp) { + struct vring_virtqueue *vq = to_vvq(_vq); + struct vring_packed_desc *desc; + struct scatterlist *sg; + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx; + __virtio16 uninitialized_var(head_flags), flags; + u16 head, avail_wrap_counter, id, cur; + bool indirect; + + START_USE(vq); + + BUG_ON(data == NULL); + BUG_ON(ctx && vq->indirect); + + if (unlikely(vq->broken)) { + END_USE(vq); + return -EIO; + } + +#ifdef DEBUG + { + ktime_t now = ktime_get(); + + /* No kick or get, with .1 second between? Warn. */ + if (vq->last_add_time_valid) + WARN_ON...

If you spend your time looking at libguestfs debugging output you'll see many messages from the daemon main loop like this: guestfsd: main_loop: new request, len 0x54 guestfsd: main_loop: proc 278 (mkfs) took 0.02 seconds I don't think these messages really bring much value. This commit removes them entirely. An alternative might be to change them to make them shorter and/or less

Hello everyone, This patch set implements packed ring support in virtio driver. Some functional tests have been done with Jason's packed ring implementation in vhost: https://lkml.org/lkml/2018/7/3/33 Both of ping and netperf worked as expected. v1 -> v2: - Use READ_ONCE() to read event off_wrap and flags together (Jason); - Add comments related to ccw (Jason); RFC (v6) -> v1: -

Hello everyone, This patch set implements packed ring support in virtio driver. Some functional tests have been done with Jason's packed ring implementation in vhost: https://lkml.org/lkml/2018/7/3/33 Both of ping and netperf worked as expected. v1 -> v2: - Use READ_ONCE() to read event off_wrap and flags together (Jason); - Add comments related to ccw (Jason); RFC (v6) -> v1: -

...gfp_t gfp) { + struct vring_virtqueue *vq = to_vvq(_vq); + struct vring_packed_desc *desc; + struct scatterlist *sg; + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx; + __virtio16 uninitialized_var(head_flags), flags; + u16 head, avail_wrap_counter, id, curr; + bool indirect; + + START_USE(vq); + + BUG_ON(data == NULL); + BUG_ON(ctx && vq->indirect); + + if (unlikely(vq->broken)) { + END_USE(vq); + return -EIO; + } + +#ifdef DEBUG + { + ktime_t now = ktime_get(); + + /* No kick or get, with .1 second between? Warn. */ + if (vq->last_add_time_valid) + WARN_ON...

...ctx, + gfp_t gfp) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + struct vring_packed_desc *desc; + struct scatterlist *sg; + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx; + __virtio16 uninitialized_var(head_flags), flags; + int head, wrap_counter; + bool indirect; + + START_USE(vq); + + BUG_ON(data == NULL); + BUG_ON(ctx && vq->indirect); + + if (unlikely(vq->broken)) { + END_USE(vq); + return -EIO; + } + +#ifdef DEBUG + { + ktime_t now = ktime_get(); + + /* No kick or get, with .1 second between? Warn. */ + if (vq->last_add_time_valid) + WARN_ON...

...ctx, + gfp_t gfp) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + struct vring_packed_desc *desc; + struct scatterlist *sg; + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx; + __virtio16 uninitialized_var(head_flags), flags; + int head, wrap_counter; + bool indirect; + + START_USE(vq); + + BUG_ON(data == NULL); + BUG_ON(ctx && vq->indirect); + + if (unlikely(vq->broken)) { + END_USE(vq); + return -EIO; + } + +#ifdef DEBUG + { + ktime_t now = ktime_get(); + + /* No kick or get, with .1 second between? Warn. */ + if (vq->last_add_time_valid) + WARN_ON...

...*vq = to_vvq(_vq); > + struct vring_packed_desc *desc; > + struct scatterlist *sg; > + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx; > + __virtio16 uninitialized_var(head_flags), flags; > + u16 head, avail_wrap_counter, id, cur; > + bool indirect; > + > + START_USE(vq); > + > + BUG_ON(data == NULL); > + BUG_ON(ctx && vq->indirect); > + > + if (unlikely(vq->broken)) { > + END_USE(vq); > + return -EIO; > + } > + > +#ifdef DEBUG > + { > + ktime_t now = ktime_get(); > + > + /* No kick or get, with .1 se...