On 07/07/2025 18:04, Caterina Shablia wrote:
> From: Boris Brezillon <boris.brezil...@collabora.com>
>
> Move the lock/flush_mem operations around the gpuvm_sm_map() calls so
> we can implement true atomic page updates, where any access in the
> locked range done by the GPU has to wait for the page table updates
> to land before proceeding.
>
> This is needed for vkQueueBindSparse(), so we can replace the dummy
> page mapped over the entire object by actual BO backed pages in an atomic
> way.
>
> Signed-off-by: Boris Brezillon <boris.brezil...@collabora.com>
> Signed-off-by: Caterina Shablia <caterina.shab...@collabora.com>
> ---
> drivers/gpu/drm/panthor/panthor_mmu.c | 65 +++++++++++++++++++++++++--
> 1 file changed, 62 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c
> b/drivers/gpu/drm/panthor/panthor_mmu.c
> index b39ea6acc6a9..9caaba03c5eb 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -387,6 +387,15 @@ struct panthor_vm {
> * flagged as faulty as a result.
> */
> bool unhandled_fault;
> +
> + /** @locked_region: Information about the currently locked region
> currently. */
> + struct {
> + /** @locked_region.start: Start of the locked region. */
> + u64 start;
> +
> + /** @locked_region.size: Size of the locked region. */
> + u64 size;
> + } locked_region;
> };
>
> /**
> @@ -775,6 +784,10 @@ int panthor_vm_active(struct panthor_vm *vm)
> }
>
> ret = panthor_mmu_as_enable(vm->ptdev, vm->as.id, transtab, transcfg,
> vm->memattr);
> + if (!ret && vm->locked_region.size) {
> + lock_region(ptdev, vm->as.id, vm->locked_region.start,
> vm->locked_region.size);
> + ret = wait_ready(ptdev, vm->as.id);
> + }
Do we need to do this? It seems odd to restore a MMU context and
immediately set a lock region. Is there a good reason we can't just
WARN_ON if there's a lock region set in panthor_vm_idle()?
I think we need to briefly take vm->op_lock to ensure synchronisation
but that doesn't seem a big issue. Or perhaps there's a good reason that
I'm missing?
>
> out_make_active:
> if (!ret) {
> @@ -902,6 +915,9 @@ static int panthor_vm_unmap_pages(struct panthor_vm *vm,
> u64 iova, u64 size)
> struct io_pgtable_ops *ops = vm->pgtbl_ops;
> u64 offset = 0;
>
> + drm_WARN_ON(&ptdev->base,
> + (iova < vm->locked_region.start) ||
> + (iova + size > vm->locked_region.start +
> vm->locked_region.size));
> drm_dbg(&ptdev->base, "unmap: as=%d, iova=%llx, len=%llx", vm->as.id,
> iova, size);
>
> while (offset < size) {
> @@ -915,13 +931,12 @@ static int panthor_vm_unmap_pages(struct panthor_vm
> *vm, u64 iova, u64 size)
> iova + offset + unmapped_sz,
> iova + offset + pgsize * pgcount,
> iova, iova + size);
> - panthor_vm_flush_range(vm, iova, offset + unmapped_sz);
> return -EINVAL;
> }
> offset += unmapped_sz;
> }
>
> - return panthor_vm_flush_range(vm, iova, size);
> + return 0;
> }
>
> static int
> @@ -938,6 +953,10 @@ panthor_vm_map_pages(struct panthor_vm *vm, u64 iova,
> int prot,
> if (!size)
> return 0;
>
> + drm_WARN_ON(&ptdev->base,
> + (iova < vm->locked_region.start) ||
> + (iova + size > vm->locked_region.start +
> vm->locked_region.size));
> +
> for_each_sgtable_dma_sg(sgt, sgl, count) {
> dma_addr_t paddr = sg_dma_address(sgl);
> size_t len = sg_dma_len(sgl);
> @@ -985,7 +1004,7 @@ panthor_vm_map_pages(struct panthor_vm *vm, u64 iova,
> int prot,
> offset = 0;
> }
>
> - return panthor_vm_flush_range(vm, start_iova, iova - start_iova);
> + return 0;
> }
>
> static int flags_to_prot(u32 flags)
> @@ -1654,6 +1673,38 @@ static const char *access_type_name(struct
> panthor_device *ptdev,
> }
> }
>
> +static int panthor_vm_lock_region(struct panthor_vm *vm, u64 start, u64 size)
> +{
> + struct panthor_device *ptdev = vm->ptdev;
> + int ret = 0;
> +
> + mutex_lock(&ptdev->mmu->as.slots_lock);
> + drm_WARN_ON(&ptdev->base, vm->locked_region.start ||
> vm->locked_region.size);
> + vm->locked_region.start = start;
> + vm->locked_region.size = size;
> + if (vm->as.id >= 0) {
> + lock_region(ptdev, vm->as.id, start, size);
> + ret = wait_ready(ptdev, vm->as.id);
> + }
> + mutex_unlock(&ptdev->mmu->as.slots_lock);
> +
> + return ret;
> +}
> +
> +static void panthor_vm_unlock_region(struct panthor_vm *vm)
> +{
> + struct panthor_device *ptdev = vm->ptdev;
> +
> + mutex_lock(&ptdev->mmu->as.slots_lock);
> + if (vm->as.id >= 0) {
> + write_cmd(ptdev, vm->as.id, AS_COMMAND_FLUSH_MEM);
> + drm_WARN_ON(&ptdev->base, wait_ready(ptdev, vm->as.id));
> + }
> + vm->locked_region.start = 0;
> + vm->locked_region.size = 0;
> + mutex_unlock(&ptdev->mmu->as.slots_lock);
> +}
Do we need to include a drm_dev_enter() somewhere here? I note that
panthor_vm_flush_range() has one and you've effectively replaced that
code with the above.
Thanks,
Steve
> +
> static void panthor_mmu_irq_handler(struct panthor_device *ptdev, u32 status)
> {
> bool has_unhandled_faults = false;
> @@ -2179,6 +2230,11 @@ panthor_vm_exec_op(struct panthor_vm *vm, struct
> panthor_vm_op_ctx *op,
>
> mutex_lock(&vm->op_lock);
> vm->op_ctx = op;
> +
> + ret = panthor_vm_lock_region(vm, op->va.addr, op->va.range);
> + if (ret)
> + goto out;
> +
> switch (op_type) {
> case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP:
> if (vm->unusable) {
> @@ -2199,6 +2255,9 @@ panthor_vm_exec_op(struct panthor_vm *vm, struct
> panthor_vm_op_ctx *op,
> break;
> }
>
> + panthor_vm_unlock_region(vm);
> +
> +out:
> if (ret && flag_vm_unusable_on_failure)
> vm->unusable = true;
>
