Currently the panthor_vm_lock_region() function will implicitly expand an already locked VM region. This can be problematic because the caller do not reliably know if it needs to call panthor_vm_unlock_region() or not.
Worth noting, there is currently no known issues with this as the code is written today. This change introduces panthor_vm_expand_region() which will only work if there is already a locked VM region. This again means that the original lock and unlock functions can work as a pair. This pairing is needed for subsequent protected memory changes. Signed-off-by: Ketil Johnsen <[email protected]> --- drivers/gpu/drm/panthor/panthor_mmu.c | 87 +++++++++++++++++++-------- 1 file changed, 62 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c index 1f6b9242279c2..b82b01013611c 100644 --- a/drivers/gpu/drm/panthor/panthor_mmu.c +++ b/drivers/gpu/drm/panthor/panthor_mmu.c @@ -1774,20 +1774,49 @@ static const char *access_type_name(struct panthor_device *ptdev, } } +static int panthor_vm_apply_as_lock(struct panthor_vm *vm, u64 region) +{ + struct panthor_device *ptdev = vm->ptdev; + + lockdep_assert_held(&ptdev->mmu->as.slots_lock); + + gpu_write64(ptdev->mmu->iomem, AS_LOCKADDR(vm->as.id), region); + return as_send_cmd_and_wait(ptdev, vm->as.id, AS_COMMAND_LOCK); +} + static int panthor_vm_lock_region(struct panthor_vm *vm, u64 start, u64 size) { struct panthor_device *ptdev = vm->ptdev; int ret = 0; - /* sm_step_remap() can call panthor_vm_lock_region() to account for - * the wider unmap needed when doing a partial huge page unamp. We - * need to ignore the lock if it's already part of the locked region. - */ - if (start >= vm->locked_region.start && - start + size <= vm->locked_region.start + vm->locked_region.size) - return 0; + if (drm_WARN_ON(&ptdev->base, vm->locked_region.size)) + return -EINVAL; + + mutex_lock(&ptdev->mmu->as.slots_lock); + if (vm->as.id >= 0 && size) { + u64 region = pack_region_range(ptdev, &start, &size); + + ret = panthor_vm_apply_as_lock(vm, region); + } - /* sm_step_remap() may need a locked region that isn't a strict superset + if (!ret) { + vm->locked_region.start = start; + vm->locked_region.size = size; + } + mutex_unlock(&ptdev->mmu->as.slots_lock); + + return ret; +} + +static int panthor_vm_expand_locked_region(struct panthor_vm *vm, + u64 start, u64 size) +{ + struct panthor_device *ptdev = vm->ptdev; + u64 end; + int ret = 0; + + /* This function is here to handle the following case: + * sm_step_remap() may need a locked region that isn't a strict superset * of the original one because of having to extend unmap boundaries beyond * it to deal with partial unmaps of transparent huge pages. What we want * in those cases is to lock the union of both regions. The new region must @@ -1795,25 +1824,30 @@ static int panthor_vm_lock_region(struct panthor_vm *vm, u64 start, u64 size) * boundaries in a remap operation can only shift up or down respectively, * but never otherwise. */ - if (vm->locked_region.size) { - u64 end = max(vm->locked_region.start + vm->locked_region.size, - start + size); - drm_WARN_ON_ONCE(&vm->ptdev->base, (start + size <= vm->locked_region.start) || - (start >= vm->locked_region.start + vm->locked_region.size)); + /* This function can only expand an already locked region */ + if (drm_WARN_ON(&ptdev->base, !vm->locked_region.size)) + return -EINVAL; + + /* Early out if requested range is already locked */ + if (start >= vm->locked_region.start && + start + size <= vm->locked_region.start + vm->locked_region.size) + return 0; - start = min(start, vm->locked_region.start); - size = end - start; - } + end = max(vm->locked_region.start + vm->locked_region.size, + start + size); + + drm_WARN_ON_ONCE(&ptdev->base, (start + size <= vm->locked_region.start) || + (start >= vm->locked_region.start + vm->locked_region.size)); + + start = min(start, vm->locked_region.start); + size = end - start; mutex_lock(&ptdev->mmu->as.slots_lock); if (vm->as.id >= 0 && size) { - /* Lock the region that needs to be updated */ - gpu_write64(ptdev->mmu->iomem, AS_LOCKADDR(vm->as.id), - pack_region_range(ptdev, &start, &size)); + u64 region = pack_region_range(ptdev, &start, &size); - /* If the lock succeeded, update the locked_region info. */ - ret = as_send_cmd_and_wait(ptdev, vm->as.id, AS_COMMAND_LOCK); + ret = panthor_vm_apply_as_lock(vm, region); } if (!ret) { @@ -2367,11 +2401,14 @@ static int panthor_gpuva_sm_step_remap(struct drm_gpuva_op *op, */ unmap_hugepage_align(&op->remap, &unmap_start, &unmap_range); - /* If the range changed, we might have to lock a wider region to guarantee - * atomicity. panthor_vm_lock_region() bails out early if the new region - * is already part of the locked region, so no need to do this check here. + /* If the range changed, we might have to lock a wider region to + * guarantee atomicity. */ - panthor_vm_lock_region(vm, unmap_start, unmap_range); + ret = panthor_vm_expand_locked_region(vm, unmap_start, + unmap_range); + if (ret) + return ret; + panthor_vm_unmap_pages(vm, unmap_start, unmap_range); } -- 2.43.0
