Si-Wei Liu
2023-Sep-09 13:31 UTC
[PATCH RFC v2 0/4] vdpa: decouple reset of iotlb mapping from device reset
In order to reduce needlessly high setup and teardown cost of iotlb mapping during live migration, it's crucial to decouple the vhost-vdpa iotlb abstraction from the virtio device life cycle, i.e. iotlb mappings should be left intact across virtio device reset [1]. For it to work, the on-chip IOMMU parent device should implement a separate .reset_map() operation callback to restore 1:1 DMA mapping without having to resort to the .reset() callback, which is mainly used to reset virtio specific device state. This new .reset_map() callback will be invoked only when the vhost-vdpa driver is to be removed and detached from the vdpa bus, such that other vdpa bus drivers, e.g. virtio-vdpa, can start with 1:1 DMA mapping when they are attached. For the context, those on-chip IOMMU parent devices, create the 1:1 DMA mapping at vdpa device add, and they would implicitly destroy the 1:1 mapping when the first .set_map or .dma_map callback is invoked. [1] Reducing vdpa migration downtime because of memory pin / maps https://www.mail-archive.com/qemu-devel at nongnu.org/msg953755.html --- RFC v2: - rebased on top of the "[PATCH RFC v2 0/3] vdpa: dedicated descriptor table group" series: https://lore.kernel.org/virtualization/1694248959-13369-1-git-send-email-si-wei.liu at oracle.com/ --- Si-Wei Liu (4): vdpa: introduce .reset_map operation callback vdpa/mlx5: implement .reset_map driver op vhost-vdpa: should restore 1:1 dma mapping before detaching driver vhost-vdpa: introduce IOTLB_PERSIST backend feature bit drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 + drivers/vdpa/mlx5/core/mr.c | 70 +++++++++++++++++++++++--------------- drivers/vdpa/mlx5/net/mlx5_vnet.c | 18 +++++++--- drivers/vhost/vdpa.c | 32 ++++++++++++++++- include/linux/vdpa.h | 7 ++++ include/uapi/linux/vhost_types.h | 2 ++ 6 files changed, 96 insertions(+), 34 deletions(-) -- 1.8.3.1
Si-Wei Liu
2023-Sep-09 13:31 UTC
[PATCH RFC v2 1/4] vdpa: introduce .reset_map operation callback
On-chip IOMMU parent driver could use it to restore memory mapping
to the initial state.
Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com>
---
include/linux/vdpa.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 17a4efa..daecf55 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -324,6 +324,12 @@ struct vdpa_map_file {
* @iova: iova to be unmapped
* @size: size of the area
* Returns integer: success (0) or error (< 0)
+ * @reset_map: Reset device memory mapping (optional)
+ * Needed for device that using device
+ * specific DMA translation (on-chip IOMMU)
+ * @vdev: vdpa device
+ * @asid: address space identifier
+ * Returns integer: success (0) or error (< 0)
* @get_vq_dma_dev: Get the dma device for a specific
* virtqueue (optional)
* @vdev: vdpa device
@@ -401,6 +407,7 @@ struct vdpa_config_ops {
u64 iova, u64 size, u64 pa, u32 perm, void *opaque);
int (*dma_unmap)(struct vdpa_device *vdev, unsigned int asid,
u64 iova, u64 size);
+ int (*reset_map)(struct vdpa_device *vdev, unsigned int asid);
int (*set_group_asid)(struct vdpa_device *vdev, unsigned int group,
unsigned int asid);
struct device *(*get_vq_dma_dev)(struct vdpa_device *vdev, u16 idx);
--
1.8.3.1
Si-Wei Liu
2023-Sep-09 13:31 UTC
[PATCH RFC v2 2/4] vdpa/mlx5: implement .reset_map driver op
Today, mlx5_vdpa gets started by preallocate 1:1 DMA mapping at
device creation time, while this 1:1 mapping will be implicitly
destroyed when the first .set_map call is invoked. Everytime
when the .reset callback is invoked, any mapping left behind will
be dropped then reset back to the initial 1:1 DMA mapping.
In order to reduce excessive memory mapping cost during live
migration, it is desirable to decouple the vhost-vdpa iotlb
abstraction from the virtio device life cycle, i.e. mappings
should be left intact across virtio device reset. Leverage the
.reset_map callback to reset memory mapping, then the device
.reset routine can run free from having to clean up memory
mappings.
Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com>
---
RFC v1 -> v2:
- fix error path when both CVQ and DVQ fall in same asid
---
drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 +
drivers/vdpa/mlx5/core/mr.c | 70 +++++++++++++++++++++++---------------
drivers/vdpa/mlx5/net/mlx5_vnet.c | 18 +++++++---
3 files changed, 56 insertions(+), 33 deletions(-)
diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
index b53420e..5c9a25a 100644
--- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
+++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
@@ -123,6 +123,7 @@ int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct
vhost_iotlb *iotlb,
unsigned int asid);
void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev);
void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev *mvdev, unsigned int asid);
+int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid);
#define mlx5_vdpa_warn(__dev, format, ...)
\
dev_warn((__dev)->mdev->device, "%s:%d:(pid %d) warning: "
format, __func__, __LINE__, \
diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
index 5a1971fc..ec2c7b4e1 100644
--- a/drivers/vdpa/mlx5/core/mr.c
+++ b/drivers/vdpa/mlx5/core/mr.c
@@ -489,21 +489,15 @@ static void destroy_user_mr(struct mlx5_vdpa_dev *mvdev,
struct mlx5_vdpa_mr *mr
}
}
-static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev, unsigned int
asid)
+static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev)
{
- if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
- return;
-
prune_iotlb(mvdev);
}
-static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev, unsigned int
asid)
+static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev)
{
struct mlx5_vdpa_mr *mr = &mvdev->mr;
- if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
- return;
-
if (!mr->initialized)
return;
@@ -521,8 +515,10 @@ void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev *mvdev,
unsigned int asid)
mutex_lock(&mr->mkey_mtx);
- _mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
- _mlx5_vdpa_destroy_cvq_mr(mvdev, asid);
+ if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid)
+ _mlx5_vdpa_destroy_dvq_mr(mvdev);
+ if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid)
+ _mlx5_vdpa_destroy_cvq_mr(mvdev);
mutex_unlock(&mr->mkey_mtx);
}
@@ -534,25 +530,17 @@ void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev)
}
static int _mlx5_vdpa_create_cvq_mr(struct mlx5_vdpa_dev *mvdev,
- struct vhost_iotlb *iotlb,
- unsigned int asid)
+ struct vhost_iotlb *iotlb)
{
- if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
- return 0;
-
return dup_iotlb(mvdev, iotlb);
}
static int _mlx5_vdpa_create_dvq_mr(struct mlx5_vdpa_dev *mvdev,
- struct vhost_iotlb *iotlb,
- unsigned int asid)
+ struct vhost_iotlb *iotlb)
{
struct mlx5_vdpa_mr *mr = &mvdev->mr;
int err;
- if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
- return 0;
-
if (mr->initialized)
return 0;
@@ -574,18 +562,22 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev
*mvdev,
{
int err;
- err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb, asid);
- if (err)
- return err;
-
- err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb, asid);
- if (err)
- goto out_err;
+ if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
+ err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb);
+ if (err)
+ return err;
+ }
+ if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid) {
+ err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb);
+ if (err)
+ goto out_err;
+ }
return 0;
out_err:
- _mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
+ if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid)
+ _mlx5_vdpa_destroy_dvq_mr(mvdev);
return err;
}
@@ -601,6 +593,28 @@ int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct
vhost_iotlb *iotlb,
return err;
}
+int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid)
+{
+ struct mlx5_vdpa_mr *mr = &mvdev->mr;
+ int err = 0;
+
+ if (asid != 0)
+ return 0;
+
+ mutex_lock(&mr->mkey_mtx);
+ if (!mr->user_mr)
+ goto out;
+ _mlx5_vdpa_destroy_dvq_mr(mvdev);
+ if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
+ err = _mlx5_vdpa_create_dvq_mr(mvdev, NULL);
+ if (err)
+ mlx5_vdpa_warn(mvdev, "create DMA MR failed\n");
+ }
+out:
+ mutex_unlock(&mr->mkey_mtx);
+ return err;
+}
+
int mlx5_vdpa_handle_set_map(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
*iotlb,
bool *change_map, unsigned int asid)
{
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 37be945..3cb5db6 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2824,7 +2824,6 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
unregister_link_notifier(ndev);
teardown_driver(ndev);
clear_vqs_ready(ndev);
- mlx5_vdpa_destroy_mr(&ndev->mvdev);
ndev->mvdev.status = 0;
ndev->mvdev.suspended = false;
ndev->cur_num_vqs = 0;
@@ -2835,10 +2834,6 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
init_group_to_asid_map(mvdev);
++mvdev->generation;
- if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
- if (mlx5_vdpa_create_mr(mvdev, NULL, 0))
- mlx5_vdpa_warn(mvdev, "create MR failed\n");
- }
up_write(&ndev->reslock);
return 0;
@@ -2903,6 +2898,18 @@ static int mlx5_vdpa_set_map(struct vdpa_device *vdev,
unsigned int asid,
return err;
}
+static int mlx5_vdpa_reset_map(struct vdpa_device *vdev, unsigned int asid)
+{
+ struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
+ struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
+ int err;
+
+ down_write(&ndev->reslock);
+ err = mlx5_vdpa_reset_mr(mvdev, asid);
+ up_write(&ndev->reslock);
+ return err;
+}
+
static struct device *mlx5_get_vq_dma_dev(struct vdpa_device *vdev, u16 idx)
{
struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
@@ -3162,6 +3169,7 @@ static int mlx5_set_group_asid(struct vdpa_device *vdev,
u32 group,
.set_config = mlx5_vdpa_set_config,
.get_generation = mlx5_vdpa_get_generation,
.set_map = mlx5_vdpa_set_map,
+ .reset_map = mlx5_vdpa_reset_map,
.set_group_asid = mlx5_set_group_asid,
.get_vq_dma_dev = mlx5_get_vq_dma_dev,
.free = mlx5_vdpa_free,
--
1.8.3.1
Si-Wei Liu
2023-Sep-09 13:31 UTC
[PATCH RFC v2 3/4] vhost-vdpa: should restore 1:1 dma mapping before detaching driver
Devices with on-chip IOMMU may need to restore iotlb to 1:1 identity
mapping from IOVA to PA. Before vhost-vdpa is going away, give them
a chance to clean up and reset iotlb back to 1:1 identify mapping
mode. This is done so that any vdpa bus driver may start with 1:1
identity mapping by default.
Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com>
---
drivers/vhost/vdpa.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index eabac06..71fbd559 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -131,6 +131,15 @@ static struct vhost_vdpa_as
*vhost_vdpa_find_alloc_as(struct vhost_vdpa *v,
return vhost_vdpa_alloc_as(v, asid);
}
+static void vhost_vdpa_reset_map(struct vhost_vdpa *v, u32 asid)
+{
+ struct vdpa_device *vdpa = v->vdpa;
+ const struct vdpa_config_ops *ops = vdpa->config;
+
+ if (ops->reset_map)
+ ops->reset_map(vdpa, asid);
+}
+
static int vhost_vdpa_remove_as(struct vhost_vdpa *v, u32 asid)
{
struct vhost_vdpa_as *as = asid_to_as(v, asid);
@@ -140,6 +149,14 @@ static int vhost_vdpa_remove_as(struct vhost_vdpa *v, u32
asid)
hlist_del(&as->hash_link);
vhost_vdpa_iotlb_unmap(v, &as->iotlb, 0ULL, 0ULL - 1, asid);
+ /*
+ * Devices with on-chip IOMMU need to restore iotlb
+ * to 1:1 identity mapping before vhost-vdpa is going
+ * to be removed and detached from the device. Give
+ * them a chance to do so, as this cannot be done
+ * efficiently via the whole-range unmap call above.
+ */
+ vhost_vdpa_reset_map(v, asid);
kfree(as);
return 0;
--
1.8.3.1
Si-Wei Liu
2023-Sep-09 13:31 UTC
[PATCH RFC v2 4/4] vhost-vdpa: introduce IOTLB_PERSIST backend feature bit
Userspace needs this feature flag to distinguish if vhost-vdpa
iotlb in the kernel supports persistent IOTLB mapping across
device reset. There are two cases that backend may claim
this feature bit on:
- parent device that has to work with platform IOMMU
- parent device with on-chip IOMMU that has the expected
.reset_map support in driver
Signed-off-by: Si-Wei Liu <si-wei.liu at oracle.com>
---
drivers/vhost/vdpa.c | 15 ++++++++++++++-
include/uapi/linux/vhost_types.h | 2 ++
2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 71fbd559..bbb1092 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -414,6 +414,14 @@ static bool vhost_vdpa_has_desc_group(const struct
vhost_vdpa *v)
return ops->get_vq_desc_group;
}
+static bool vhost_vdpa_has_persistent_map(const struct vhost_vdpa *v)
+{
+ struct vdpa_device *vdpa = v->vdpa;
+ const struct vdpa_config_ops *ops = vdpa->config;
+
+ return (!ops->set_map && !ops->dma_map) || ops->reset_map;
+}
+
static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
{
struct vdpa_device *vdpa = v->vdpa;
@@ -716,7 +724,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
if (features & ~(VHOST_VDPA_BACKEND_FEATURES |
BIT_ULL(VHOST_BACKEND_F_DESC_ASID) |
BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
- BIT_ULL(VHOST_BACKEND_F_RESUME)))
+ BIT_ULL(VHOST_BACKEND_F_RESUME) |
+ BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST)))
return -EOPNOTSUPP;
if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
!vhost_vdpa_can_suspend(v))
@@ -729,6 +738,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
return -EINVAL;
if ((features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID)) &&
!vhost_vdpa_has_desc_group(v))
+ if ((features & BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST)) &&
+ !vhost_vdpa_has_persistent_map(v))
return -EOPNOTSUPP;
vhost_set_backend_features(&v->vdev, features);
return 0;
@@ -785,6 +796,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
features |= BIT_ULL(VHOST_BACKEND_F_RESUME);
if (vhost_vdpa_has_desc_group(v))
features |= BIT_ULL(VHOST_BACKEND_F_DESC_ASID);
+ if (vhost_vdpa_has_persistent_map(v))
+ features |= BIT_ULL(VHOST_BACKEND_F_IOTLB_PERSIST);
if (copy_to_user(featurep, &features, sizeof(features)))
r = -EFAULT;
break;
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 6acc604..0fdb6f0 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -186,5 +186,7 @@ struct vhost_vdpa_iova_range {
* buffers may reside. Requires VHOST_BACKEND_F_IOTLB_ASID.
*/
#define VHOST_BACKEND_F_DESC_ASID 0x6
+/* IOTLB don't flush memory mapping across device reset */
+#define VHOST_BACKEND_F_IOTLB_PERSIST 0x7
#endif
--
1.8.3.1