On Fri, Aug 18, 2023 at 05:08:45PM +0200, Thomas Hellström wrote:
> Support pinning of vmas using XE_VM_BIND_FLAG_PIN, initially for userptr
> only. Pinned memory becomes accounted against RLIMIT_MEMLOCK and processes
> with CAP_IPC_LOCK will not apply the limit. This is pretty similar to
> mlock()'ing userptr memory with the added benefit that the driver is
> aware and can ignore some actions in the MMU invalidation notifier.
>
> This will initially become useful for compute VMs on hardware without
> mid-thread-preemption capability since with pinned pages, the MMU
> invalidation notifier never tries to preempt a running compute kernel.
>
> If that were the only usage we could restrict this to a flag that always
> pins userptr VMAs on compute VMs on such hardware, but there are
> indications that this may become needed in other situations as well.
>
> From a more general point of view, the usage pattern of a system may be
> such that in most cases it only ever runs a single workload per system
> and then the sysadmin would want to configure the system to allow
> extensive pinning for performance reasons.
>
> Hence we might want to extend the pinning capability to bo-backed VMAs
> as well. How that pinning will be accounted remains an open but to build
> on the current drm CGROUP work would be an option.
>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Patch LGTM but a few comments that are currently out of scope but want
to get out there for future work.
> ---
> drivers/gpu/drm/xe/xe_vm.c | 33 +++++++++++++++++++++++++-------
> drivers/gpu/drm/xe/xe_vm_types.h | 2 ++
> include/uapi/drm/xe_drm.h | 18 +++++++++++++++++
> 3 files changed, 46 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index d9c000689002..3832f1f21def 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -936,6 +936,7 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
> u64 start, u64 end,
> bool read_only,
> bool is_null,
> + bool pin,
> u8 tile_mask)
> {
> struct xe_vma *vma;
> @@ -967,6 +968,8 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
> vma->gpuva.flags |= XE_VMA_READ_ONLY;
> if (is_null)
> vma->gpuva.flags |= DRM_GPUVA_SPARSE;
> + if (pin)
> + vma->gpuva.flags |= XE_VMA_PINNED;
>
> if (tile_mask) {
> vma->tile_mask = tile_mask;
> @@ -2367,6 +2370,7 @@ vm_bind_ioctl_ops_create(struct xe_vm *vm, struct xe_bo *bo,
> op->map.read_only =
> operation & XE_VM_BIND_FLAG_READONLY;
> op->map.is_null = operation & XE_VM_BIND_FLAG_NULL;
> + op->map.pin = operation & XE_VM_BIND_FLAG_PIN;
> }
> break;
> case XE_VM_BIND_OP_UNMAP:
> @@ -2431,7 +2435,8 @@ vm_bind_ioctl_ops_create(struct xe_vm *vm, struct xe_bo *bo,
> }
>
> static struct xe_vma *new_vma(struct xe_vm *vm, struct drm_gpuva_op_map *op,
> - u8 tile_mask, bool read_only, bool is_null)
> + u8 tile_mask, bool read_only, bool is_null,
> + bool pin)
> {
> struct xe_bo *bo = op->gem.obj ? gem_to_xe_bo(op->gem.obj) : NULL;
> struct xe_vma *vma;
> @@ -2447,7 +2452,7 @@ static struct xe_vma *new_vma(struct xe_vm *vm, struct drm_gpuva_op_map *op,
> }
> vma = xe_vma_create(vm, bo, op->gem.offset,
> op->va.addr, op->va.addr +
> - op->va.range - 1, read_only, is_null,
> + op->va.range - 1, read_only, is_null, pin,
> tile_mask);
> if (bo)
> xe_bo_unlock(bo, &ww);
> @@ -2562,7 +2567,7 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
>
> vma = new_vma(vm, &op->base.map,
> op->tile_mask, op->map.read_only,
> - op->map.is_null);
> + op->map.is_null, op->map.pin);
> if (IS_ERR(vma)) {
> err = PTR_ERR(vma);
> goto free_fence;
> @@ -2587,10 +2592,13 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
> bool is_null =
> op->base.remap.unmap->va->flags &
> DRM_GPUVA_SPARSE;
> + bool pin =
> + op->base.remap.unmap->va->flags &
> + XE_VMA_PINNED;
We probably should move the read_only, is_null, and pin check out of the
next / prev if statements to just below the DRM_GPUVA_OP_REMAP case
statement.
>
> vma = new_vma(vm, op->base.remap.prev,
> op->tile_mask, read_only,
> - is_null);
> + is_null, pin);
> if (IS_ERR(vma)) {
> err = PTR_ERR(vma);
> goto free_fence;
> @@ -2623,10 +2631,13 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct xe_exec_queue *q,
> bool is_null =
> op->base.remap.unmap->va->flags &
> DRM_GPUVA_SPARSE;
> + bool pin =
> + op->base.remap.unmap->va->flags &
> + XE_VMA_PINNED;
>
> vma = new_vma(vm, op->base.remap.next,
> op->tile_mask, read_only,
> - is_null);
> + is_null, pin);
> if (IS_ERR(vma)) {
> err = PTR_ERR(vma);
> goto free_fence;
> @@ -3131,11 +3142,12 @@ static void vm_bind_ioctl_ops_unwind(struct xe_vm *vm,
> #define SUPPORTED_FLAGS \
> (FORCE_ASYNC_OP_ERROR | XE_VM_BIND_FLAG_ASYNC | \
> XE_VM_BIND_FLAG_READONLY | XE_VM_BIND_FLAG_IMMEDIATE | \
> - XE_VM_BIND_FLAG_NULL | 0xffff)
> + XE_VM_BIND_FLAG_NULL | XE_VM_BIND_FLAG_PIN | 0xffff)
> #else
> #define SUPPORTED_FLAGS \
> (XE_VM_BIND_FLAG_ASYNC | XE_VM_BIND_FLAG_READONLY | \
> - XE_VM_BIND_FLAG_IMMEDIATE | XE_VM_BIND_FLAG_NULL | 0xffff)
> + XE_VM_BIND_FLAG_IMMEDIATE | XE_VM_BIND_FLAG_NULL | \
> + XE_VM_BIND_FLAG_PIN | 0xffff)
> #endif
> #define XE_64K_PAGE_MASK 0xffffull
>
> @@ -3205,6 +3217,13 @@ static int vm_bind_ioctl_check_args(struct xe_device *xe,
> goto free_bind_ops;
> }
>
> + /* TODO: Support OP_PREFETCH, OP_MAP */
> + if (XE_IOCTL_DBG(xe, (op & XE_VM_BIND_FLAG_PIN) &&
> + VM_BIND_OP(op) != XE_VM_BIND_OP_MAP_USERPTR)) {
> + err = -EINVAL;
> + goto free_bind_ops;
> + }
> +
> if (XE_IOCTL_DBG(xe, VM_BIND_OP(op) >
> XE_VM_BIND_OP_PREFETCH) ||
> XE_IOCTL_DBG(xe, op & ~SUPPORTED_FLAGS) ||
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
> index 9b90e649cd69..024ccabadd12 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -360,6 +360,8 @@ struct xe_vma_op_map {
> bool read_only;
> /** @is_null: is NULL binding */
> bool is_null;
> + /** @pin: pin underlying memory */
> + bool pin;
> };
>
> /** struct xe_vma_op_remap - VMA remap operation */
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index 86f16d50e9cc..fc3d9cd4f8d0 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -631,6 +631,24 @@ struct drm_xe_vm_bind_op {
> * intended to implement VK sparse bindings.
> */
> #define XE_VM_BIND_FLAG_NULL (0x1 << 19)
> + /*
> + * When the PIN flag is set, the user requests the underlying
> + * backing store of the vma to be pinned, that is, it will be
> + * resident while bound and the underlying physical memory
> + * will not change. For userptr VMAs this means that if the
> + * user performs an operation that changes the underlying
> + * pages of the CPU virtual space, the corresponding pinned
> + * GPU virtual space will not pick up the new memory unless
> + * an OP_UNMAP followed by a OP_MAP_USERPTR is performed.
> + * Pinned userptr memory is accounted in the same way as
> + * mlock(2), and if pinning fails the following error codes
> + * may be returned:
> + * -EINVAL: The memory region does not support pinning.
> + * -EPERM: The process is not permitted to pin.
> + * -ENOMEM: The pinning limit does not allow pinning.
> + * For userptr memory, CAP_IPC_LOCK will bypass the limit checking.
> + */
> +#define XE_VM_BIND_FLAG_PIN (0x1 << 20)
We are quickly using a lot of the upper bits, maybe we change the op
field to a __u64 soon? We have to break the VM bind api when removing
the async worker + updating sync mode to align with VM bind doc, maybe
we change this then too?
Anyways this patch LGTM:
Reviewed-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> /** @op: Operation to perform (lower 16 bits) and flags (upper 16 bits) */
> __u32 op;
>
> --
> 2.41.0
>
