Re: [PATCH RFC v2 02/10] vringh: add 'iotlb_lock' to synchronize iotlb accesses
On 2021/1/29 下午5:18, Stefano Garzarella wrote: On Fri, Jan 29, 2021 at 03:43:40PM +0800, Jason Wang wrote: On 2021/1/28 下午10:41, Stefano Garzarella wrote: Usually iotlb accesses are synchronized with a spinlock. Let's request it as a new parameter in vringh_set_iotlb() and hold it when we navigate the iotlb in iotlb_translate() to avoid race conditions with any new additions/deletions of ranges from the ioltb. Patch looks fine but I wonder if this is the best approach comparing to do locking by the caller. Initially I tried to hold the lock in the vdpasim_blk_work(), but since we have a lot of different functions for vringh, I opted to take the lock at the beginning and release it at the end. Also because several times I went to see if that call used iotlb_translate or not. This could be a problem for example if we have multiple workers to handle multiple queues. Also, some functions are quite long (e.g. vringh_getdesc_iotlb) and holding the lock for that long could reduce parallelism. For these reasons I thought it was better to hide everything from the caller who doesn't have to worry about which function calls iotlb_translate() and thus hold the lock. Fine with me. Acked-by: Jason Wang Thanks Thanks, Stefano Thanks Signed-off-by: Stefano Garzarella --- include/linux/vringh.h | 6 +- drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- drivers/vhost/vringh.c | 9 - 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/include/linux/vringh.h b/include/linux/vringh.h index 59bd50f99291..9c077863c8f6 100644 --- a/include/linux/vringh.h +++ b/include/linux/vringh.h @@ -46,6 +46,9 @@ struct vringh { /* IOTLB for this vring */ struct vhost_iotlb *iotlb; + /* spinlock to synchronize IOTLB accesses */ + spinlock_t *iotlb_lock; + /* The function to call to notify the guest about added buffers */ void (*notify)(struct vringh *); }; @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) #if IS_REACHABLE(CONFIG_VHOST_IOTLB) -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock); int vringh_init_iotlb(struct vringh *vrh, u64 features, unsigned int num, bool weak_barriers, diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c index 2183a833fcf4..53238989713d 100644 --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr) goto err_iommu; for (i = 0; i < dev_attr->nvqs; i++) - vringh_set_iotlb(>vqs[i].vring, vdpasim->iommu); + vringh_set_iotlb(>vqs[i].vring, vdpasim->iommu, + >iommu_lock); ret = iova_cache_get(); if (ret) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 85d85faba058..f68122705719 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh *vrh, int ret = 0; u64 s = 0; + spin_lock(vrh->iotlb_lock); + while (len > s) { u64 size, pa, pfn; @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh *vrh, ++ret; } + spin_unlock(vrh->iotlb_lock); + return ret; } @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. * @vrh: the vring * @iotlb: iotlb associated with this vring + * @iotlb_lock: spinlock to synchronize the iotlb accesses */ -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock) { vrh->iotlb = iotlb; + vrh->iotlb_lock = iotlb_lock; } EXPORT_SYMBOL(vringh_set_iotlb);
Re: [PATCH RFC v2 02/10] vringh: add 'iotlb_lock' to synchronize iotlb accesses
On 2021/1/28 下午10:41, Stefano Garzarella wrote: Usually iotlb accesses are synchronized with a spinlock. Let's request it as a new parameter in vringh_set_iotlb() and hold it when we navigate the iotlb in iotlb_translate() to avoid race conditions with any new additions/deletions of ranges from the ioltb. Patch looks fine but I wonder if this is the best approach comparing to do locking by the caller. Thanks Signed-off-by: Stefano Garzarella --- include/linux/vringh.h | 6 +- drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- drivers/vhost/vringh.c | 9 - 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/include/linux/vringh.h b/include/linux/vringh.h index 59bd50f99291..9c077863c8f6 100644 --- a/include/linux/vringh.h +++ b/include/linux/vringh.h @@ -46,6 +46,9 @@ struct vringh { /* IOTLB for this vring */ struct vhost_iotlb *iotlb; + /* spinlock to synchronize IOTLB accesses */ + spinlock_t *iotlb_lock; + /* The function to call to notify the guest about added buffers */ void (*notify)(struct vringh *); }; @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) #if IS_REACHABLE(CONFIG_VHOST_IOTLB) -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock); int vringh_init_iotlb(struct vringh *vrh, u64 features, unsigned int num, bool weak_barriers, diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c index 2183a833fcf4..53238989713d 100644 --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr) goto err_iommu; for (i = 0; i < dev_attr->nvqs; i++) - vringh_set_iotlb(>vqs[i].vring, vdpasim->iommu); + vringh_set_iotlb(>vqs[i].vring, vdpasim->iommu, +>iommu_lock); ret = iova_cache_get(); if (ret) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 85d85faba058..f68122705719 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh *vrh, int ret = 0; u64 s = 0; + spin_lock(vrh->iotlb_lock); + while (len > s) { u64 size, pa, pfn; @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh *vrh, ++ret; } + spin_unlock(vrh->iotlb_lock); + return ret; } @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. * @vrh: the vring * @iotlb: iotlb associated with this vring + * @iotlb_lock: spinlock to synchronize the iotlb accesses */ -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock) { vrh->iotlb = iotlb; + vrh->iotlb_lock = iotlb_lock; } EXPORT_SYMBOL(vringh_set_iotlb);
[PATCH RFC v2 02/10] vringh: add 'iotlb_lock' to synchronize iotlb accesses
Usually iotlb accesses are synchronized with a spinlock. Let's request it as a new parameter in vringh_set_iotlb() and hold it when we navigate the iotlb in iotlb_translate() to avoid race conditions with any new additions/deletions of ranges from the ioltb. Signed-off-by: Stefano Garzarella --- include/linux/vringh.h | 6 +- drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- drivers/vhost/vringh.c | 9 - 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/include/linux/vringh.h b/include/linux/vringh.h index 59bd50f99291..9c077863c8f6 100644 --- a/include/linux/vringh.h +++ b/include/linux/vringh.h @@ -46,6 +46,9 @@ struct vringh { /* IOTLB for this vring */ struct vhost_iotlb *iotlb; + /* spinlock to synchronize IOTLB accesses */ + spinlock_t *iotlb_lock; + /* The function to call to notify the guest about added buffers */ void (*notify)(struct vringh *); }; @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) #if IS_REACHABLE(CONFIG_VHOST_IOTLB) -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock); int vringh_init_iotlb(struct vringh *vrh, u64 features, unsigned int num, bool weak_barriers, diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c index 2183a833fcf4..53238989713d 100644 --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr) goto err_iommu; for (i = 0; i < dev_attr->nvqs; i++) - vringh_set_iotlb(>vqs[i].vring, vdpasim->iommu); + vringh_set_iotlb(>vqs[i].vring, vdpasim->iommu, +>iommu_lock); ret = iova_cache_get(); if (ret) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 85d85faba058..f68122705719 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh *vrh, int ret = 0; u64 s = 0; + spin_lock(vrh->iotlb_lock); + while (len > s) { u64 size, pa, pfn; @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh *vrh, ++ret; } + spin_unlock(vrh->iotlb_lock); + return ret; } @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. * @vrh: the vring * @iotlb: iotlb associated with this vring + * @iotlb_lock: spinlock to synchronize the iotlb accesses */ -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock) { vrh->iotlb = iotlb; + vrh->iotlb_lock = iotlb_lock; } EXPORT_SYMBOL(vringh_set_iotlb); -- 2.29.2