January 2025 - Linux-stable-mirror

[PATCH AUTOSEL 6.6 01/17] drm/virtio: New fence for every plane update

by Sasha Levin

From: Dongwon Kim <dongwon.kim(a)intel.com> [ Upstream commit d3c55b8ab6fe5fa2e7ab02efd36d09c39ee5022f ] Having a fence linked to a virtio_gpu_framebuffer in the plane update sequence would cause conflict when several planes referencing the same framebuffer (e.g. Xorg screen covering multi-displays configured for an extended mode) and those planes are updated concurrently. So it is needed to allocate a fence for every plane state instead of the framebuffer. Signed-off-by: Dongwon Kim <dongwon.kim(a)intel.com> [dmitry.osipenko(a)collabora.com: rebase, fix up, edit commit message] Signed-off-by: Dmitry Osipenko <dmitry.osipenko(a)collabora.com> Acked-by: Vivek Kasireddy <vivek.kasireddy(a)intel.com> Reviewed-by: Rob Clark <robdclark(a)gmail.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241020230803.247419-2-dmitr… Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- drivers/gpu/drm/virtio/virtgpu_drv.h | 7 ++++ drivers/gpu/drm/virtio/virtgpu_plane.c | 58 +++++++++++++++++--------- 2 files changed, 46 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h index 4126c384286bf..61fd37f95fbd9 100644 --- a/drivers/gpu/drm/virtio/virtgpu_drv.h +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h @@ -191,6 +191,13 @@ struct virtio_gpu_framebuffer { #define to_virtio_gpu_framebuffer(x) \ container_of(x, struct virtio_gpu_framebuffer, base) +struct virtio_gpu_plane_state { + struct drm_plane_state base; + struct virtio_gpu_fence *fence; +}; +#define to_virtio_gpu_plane_state(x) \ + container_of(x, struct virtio_gpu_plane_state, base) + struct virtio_gpu_queue { struct virtqueue *vq; spinlock_t qlock; diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c index a1ef657eba077..36de73e03bbfa 100644 --- a/drivers/gpu/drm/virtio/virtgpu_plane.c +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c @@ -66,11 +66,28 @@ uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc) return format; } +static struct +drm_plane_state *virtio_gpu_plane_duplicate_state(struct drm_plane *plane) +{ + struct virtio_gpu_plane_state *new; + + if (WARN_ON(!plane->state)) + return NULL; + + new = kzalloc(sizeof(*new), GFP_KERNEL); + if (!new) + return NULL; + + __drm_atomic_helper_plane_duplicate_state(plane, &new->base); + + return &new->base; +} + static const struct drm_plane_funcs virtio_gpu_plane_funcs = { .update_plane = drm_atomic_helper_update_plane, .disable_plane = drm_atomic_helper_disable_plane, .reset = drm_atomic_helper_plane_reset, - .atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state, + .atomic_duplicate_state = virtio_gpu_plane_duplicate_state, .atomic_destroy_state = drm_atomic_helper_plane_destroy_state, }; @@ -138,11 +155,13 @@ static void virtio_gpu_resource_flush(struct drm_plane *plane, struct drm_device *dev = plane->dev; struct virtio_gpu_device *vgdev = dev->dev_private; struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; struct virtio_gpu_object *bo; vgfb = to_virtio_gpu_framebuffer(plane->state->fb); + vgplane_st = to_virtio_gpu_plane_state(plane->state); bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]); - if (vgfb->fence) { + if (vgplane_st->fence) { struct virtio_gpu_object_array *objs; objs = virtio_gpu_array_alloc(1); @@ -151,13 +170,11 @@ static void virtio_gpu_resource_flush(struct drm_plane *plane, virtio_gpu_array_add_obj(objs, vgfb->base.obj[0]); virtio_gpu_array_lock_resv(objs); virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle, x, y, - width, height, objs, vgfb->fence); + width, height, objs, + vgplane_st->fence); virtio_gpu_notify(vgdev); - - dma_fence_wait_timeout(&vgfb->fence->f, true, + dma_fence_wait_timeout(&vgplane_st->fence->f, true, msecs_to_jiffies(50)); - dma_fence_put(&vgfb->fence->f); - vgfb->fence = NULL; } else { virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle, x, y, width, height, NULL, NULL); @@ -247,20 +264,23 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane *plane, struct drm_device *dev = plane->dev; struct virtio_gpu_device *vgdev = dev->dev_private; struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; struct virtio_gpu_object *bo; if (!new_state->fb) return 0; vgfb = to_virtio_gpu_framebuffer(new_state->fb); + vgplane_st = to_virtio_gpu_plane_state(new_state); bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]); if (!bo || (plane->type == DRM_PLANE_TYPE_PRIMARY && !bo->guest_blob)) return 0; - if (bo->dumb && (plane->state->fb != new_state->fb)) { - vgfb->fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context, + if (bo->dumb) { + vgplane_st->fence = virtio_gpu_fence_alloc(vgdev, + vgdev->fence_drv.context, 0); - if (!vgfb->fence) + if (!vgplane_st->fence) return -ENOMEM; } @@ -270,15 +290,15 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane *plane, static void virtio_gpu_plane_cleanup_fb(struct drm_plane *plane, struct drm_plane_state *state) { - struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; if (!state->fb) return; - vgfb = to_virtio_gpu_framebuffer(state->fb); - if (vgfb->fence) { - dma_fence_put(&vgfb->fence->f); - vgfb->fence = NULL; + vgplane_st = to_virtio_gpu_plane_state(state); + if (vgplane_st->fence) { + dma_fence_put(&vgplane_st->fence->f); + vgplane_st->fence = NULL; } } @@ -291,6 +311,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, struct virtio_gpu_device *vgdev = dev->dev_private; struct virtio_gpu_output *output = NULL; struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; struct virtio_gpu_object *bo = NULL; uint32_t handle; @@ -303,6 +324,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, if (plane->state->fb) { vgfb = to_virtio_gpu_framebuffer(plane->state->fb); + vgplane_st = to_virtio_gpu_plane_state(plane->state); bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]); handle = bo->hw_res_handle; } else { @@ -322,11 +344,9 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, (vgdev, 0, plane->state->crtc_w, plane->state->crtc_h, - 0, 0, objs, vgfb->fence); + 0, 0, objs, vgplane_st->fence); virtio_gpu_notify(vgdev); - dma_fence_wait(&vgfb->fence->f, true); - dma_fence_put(&vgfb->fence->f); - vgfb->fence = NULL; + dma_fence_wait(&vgplane_st->fence->f, true); } if (plane->state->fb != old_state->fb) { -- 2.39.5

2 months, 3 weeks

1
16
0 0

[PATCH AUTOSEL 6.13 01/34] drm/virtio: New fence for every plane update

by Sasha Levin

From: Dongwon Kim <dongwon.kim(a)intel.com> [ Upstream commit d3c55b8ab6fe5fa2e7ab02efd36d09c39ee5022f ] Having a fence linked to a virtio_gpu_framebuffer in the plane update sequence would cause conflict when several planes referencing the same framebuffer (e.g. Xorg screen covering multi-displays configured for an extended mode) and those planes are updated concurrently. So it is needed to allocate a fence for every plane state instead of the framebuffer. Signed-off-by: Dongwon Kim <dongwon.kim(a)intel.com> [dmitry.osipenko(a)collabora.com: rebase, fix up, edit commit message] Signed-off-by: Dmitry Osipenko <dmitry.osipenko(a)collabora.com> Acked-by: Vivek Kasireddy <vivek.kasireddy(a)intel.com> Reviewed-by: Rob Clark <robdclark(a)gmail.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241020230803.247419-2-dmitr… Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- drivers/gpu/drm/virtio/virtgpu_drv.h | 7 ++++ drivers/gpu/drm/virtio/virtgpu_plane.c | 58 +++++++++++++++++--------- 2 files changed, 46 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h index 64c236169db88..5dc8eeaf7123c 100644 --- a/drivers/gpu/drm/virtio/virtgpu_drv.h +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h @@ -194,6 +194,13 @@ struct virtio_gpu_framebuffer { #define to_virtio_gpu_framebuffer(x) \ container_of(x, struct virtio_gpu_framebuffer, base) +struct virtio_gpu_plane_state { + struct drm_plane_state base; + struct virtio_gpu_fence *fence; +}; +#define to_virtio_gpu_plane_state(x) \ + container_of(x, struct virtio_gpu_plane_state, base) + struct virtio_gpu_queue { struct virtqueue *vq; spinlock_t qlock; diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c index a72a2dbda031c..7acd38b962c62 100644 --- a/drivers/gpu/drm/virtio/virtgpu_plane.c +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c @@ -66,11 +66,28 @@ uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc) return format; } +static struct +drm_plane_state *virtio_gpu_plane_duplicate_state(struct drm_plane *plane) +{ + struct virtio_gpu_plane_state *new; + + if (WARN_ON(!plane->state)) + return NULL; + + new = kzalloc(sizeof(*new), GFP_KERNEL); + if (!new) + return NULL; + + __drm_atomic_helper_plane_duplicate_state(plane, &new->base); + + return &new->base; +} + static const struct drm_plane_funcs virtio_gpu_plane_funcs = { .update_plane = drm_atomic_helper_update_plane, .disable_plane = drm_atomic_helper_disable_plane, .reset = drm_atomic_helper_plane_reset, - .atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state, + .atomic_duplicate_state = virtio_gpu_plane_duplicate_state, .atomic_destroy_state = drm_atomic_helper_plane_destroy_state, }; @@ -138,11 +155,13 @@ static void virtio_gpu_resource_flush(struct drm_plane *plane, struct drm_device *dev = plane->dev; struct virtio_gpu_device *vgdev = dev->dev_private; struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; struct virtio_gpu_object *bo; vgfb = to_virtio_gpu_framebuffer(plane->state->fb); + vgplane_st = to_virtio_gpu_plane_state(plane->state); bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]); - if (vgfb->fence) { + if (vgplane_st->fence) { struct virtio_gpu_object_array *objs; objs = virtio_gpu_array_alloc(1); @@ -151,13 +170,11 @@ static void virtio_gpu_resource_flush(struct drm_plane *plane, virtio_gpu_array_add_obj(objs, vgfb->base.obj[0]); virtio_gpu_array_lock_resv(objs); virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle, x, y, - width, height, objs, vgfb->fence); + width, height, objs, + vgplane_st->fence); virtio_gpu_notify(vgdev); - - dma_fence_wait_timeout(&vgfb->fence->f, true, + dma_fence_wait_timeout(&vgplane_st->fence->f, true, msecs_to_jiffies(50)); - dma_fence_put(&vgfb->fence->f); - vgfb->fence = NULL; } else { virtio_gpu_cmd_resource_flush(vgdev, bo->hw_res_handle, x, y, width, height, NULL, NULL); @@ -247,20 +264,23 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane *plane, struct drm_device *dev = plane->dev; struct virtio_gpu_device *vgdev = dev->dev_private; struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; struct virtio_gpu_object *bo; if (!new_state->fb) return 0; vgfb = to_virtio_gpu_framebuffer(new_state->fb); + vgplane_st = to_virtio_gpu_plane_state(new_state); bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]); if (!bo || (plane->type == DRM_PLANE_TYPE_PRIMARY && !bo->guest_blob)) return 0; - if (bo->dumb && (plane->state->fb != new_state->fb)) { - vgfb->fence = virtio_gpu_fence_alloc(vgdev, vgdev->fence_drv.context, + if (bo->dumb) { + vgplane_st->fence = virtio_gpu_fence_alloc(vgdev, + vgdev->fence_drv.context, 0); - if (!vgfb->fence) + if (!vgplane_st->fence) return -ENOMEM; } @@ -270,15 +290,15 @@ static int virtio_gpu_plane_prepare_fb(struct drm_plane *plane, static void virtio_gpu_plane_cleanup_fb(struct drm_plane *plane, struct drm_plane_state *state) { - struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; if (!state->fb) return; - vgfb = to_virtio_gpu_framebuffer(state->fb); - if (vgfb->fence) { - dma_fence_put(&vgfb->fence->f); - vgfb->fence = NULL; + vgplane_st = to_virtio_gpu_plane_state(state); + if (vgplane_st->fence) { + dma_fence_put(&vgplane_st->fence->f); + vgplane_st->fence = NULL; } } @@ -291,6 +311,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, struct virtio_gpu_device *vgdev = dev->dev_private; struct virtio_gpu_output *output = NULL; struct virtio_gpu_framebuffer *vgfb; + struct virtio_gpu_plane_state *vgplane_st; struct virtio_gpu_object *bo = NULL; uint32_t handle; @@ -303,6 +324,7 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, if (plane->state->fb) { vgfb = to_virtio_gpu_framebuffer(plane->state->fb); + vgplane_st = to_virtio_gpu_plane_state(plane->state); bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]); handle = bo->hw_res_handle; } else { @@ -322,11 +344,9 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane *plane, (vgdev, 0, plane->state->crtc_w, plane->state->crtc_h, - 0, 0, objs, vgfb->fence); + 0, 0, objs, vgplane_st->fence); virtio_gpu_notify(vgdev); - dma_fence_wait(&vgfb->fence->f, true); - dma_fence_put(&vgfb->fence->f); - vgfb->fence = NULL; + dma_fence_wait(&vgplane_st->fence->f, true); } if (plane->state->fb != old_state->fb) { -- 2.39.5

2 months, 3 weeks

1
33
0 0

[PATCH AUTOSEL 5.4 1/2] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 51ac62637e4ed..39ce8a3d8c573 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -176,13 +176,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

1
1
0 0

[PATCH AUTOSEL 5.10 1/3] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7cf45d506688c..42dad8c8d6f28 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -279,13 +279,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

1
2
0 0

[PATCH AUTOSEL 5.15 1/3] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ed92b75f7e024..691af58c156e1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -642,13 +642,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

1
2
0 0

[PATCH AUTOSEL 6.1 1/3] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 54af671e8d510..3927904984fd5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -704,13 +704,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

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[PATCH AUTOSEL 6.6 1/3] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 86606fb9e6bc6..c686d826a91cf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -726,13 +726,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

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[PATCH AUTOSEL 6.12 1/7] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d07dc87787dff..9015c792830c2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -766,13 +766,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

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[PATCH AUTOSEL 6.13 1/7] sched: Don't try to catch up excess steal time.

by Sasha Levin

From: Suleiman Souhlal <suleiman(a)google.com> [ Upstream commit 108ad0999085df2366dd9ef437573955cb3f5586 ] When steal time exceeds the measured delta when updating clock_task, we currently try to catch up the excess in future updates. However, this results in inaccurate run times for the future things using clock_task, in some situations, as they end up getting additional steal time that did not actually happen. This is because there is a window between reading the elapsed time in update_rq_clock() and sampling the steal time in update_rq_clock_task(). If the VCPU gets preempted between those two points, any additional steal time is accounted to the outgoing task even though the calculated delta did not actually contain any of that "stolen" time. When this race happens, we can end up with steal time that exceeds the calculated delta, and the previous code would try to catch up that excess steal time in future clock updates, which is given to the next, incoming task, even though it did not actually have any time stolen. This behavior is particularly bad when steal time can be very long, which we've seen when trying to extend steal time to contain the duration that the host was suspended [0]. When this happens, clock_task stays frozen, during which the running task stays running for the whole duration, since its run time doesn't increase. However the race can happen even under normal operation. Ideally we would read the elapsed cpu time and the steal time atomically, to prevent this race from happening in the first place, but doing so is non-trivial. Since the time between those two points isn't otherwise accounted anywhere, neither to the outgoing task nor the incoming task (because the "end of outgoing task" and "start of incoming task" timestamps are the same), I would argue that the right thing to do is to simply drop any excess steal time, in order to prevent these issues. [0] https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@google.com/ Signed-off-by: Suleiman Souhlal <suleiman(a)google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://lore.kernel.org/r/20241118043745.1857272-1-suleiman@google.com Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3e5a6bf587f91..296e77380318e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -766,13 +766,15 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((&paravirt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif -- 2.39.5

2 months, 3 weeks

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0 0

[PATCH AUTOSEL 5.4] btrfs: convert BUG_ON in btrfs_reloc_cow_block() to proper error handling

by Sasha Levin

From: Josef Bacik <josef(a)toxicpanda.com> [ Upstream commit 6a4730b325aaa48f7a5d5ba97aff0a955e2d9cec ] This BUG_ON is meant to catch backref cache problems, but these can arise from either bugs in the backref cache or corruption in the extent tree. Fix it to be a proper error. Reviewed-by: Boris Burkov <boris(a)bur.io> Signed-off-by: Josef Bacik <josef(a)toxicpanda.com> Reviewed-by: David Sterba <dsterba(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- fs/btrfs/relocation.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 89ad7e12c08bb..062154c6a65f6 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -4789,8 +4789,18 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans, WARN_ON(!first_cow && level == 0); node = rc->backref_cache.path[level]; - BUG_ON(node->bytenr != buf->start && - node->new_bytenr != buf->start); + + /* + * If node->bytenr != buf->start and node->new_bytenr != + * buf->start then we've got the wrong backref node for what we + * expected to see here and the cache is incorrect. + */ + if (unlikely(node->bytenr != buf->start && node->new_bytenr != buf->start)) { + btrfs_err(fs_info, +"bytenr %llu was found but our backref cache was expecting %llu or %llu", + buf->start, node->bytenr, node->new_bytenr); + return -EUCLEAN; + } drop_node_buffer(node); extent_buffer_get(cow); -- 2.39.5

2 months, 3 weeks

1
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