On Fri, 2024-12-20 at 13:31 +0200, Mika Kuoppala wrote:
> Implement debugger vm access for userptrs.
>
> When bind is done, take ref to current task so that
> we know from which vm the address was bound. Then during
> debugger pread/pwrite we use this target task as
> parameter to access the debuggee vm with access_process_vm().
>
> This is based on suggestions from Thomas, Joonas and Simona.
>
> v2: need to add offset into vma (Dominik)
>
> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Cc: Dominik Grzegorzek <dominik.grzegorzek@xxxxxxxxx>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Simona Vetter <simona@xxxxxxxx>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/xe/xe_eudebug.c | 13 +++++++++++++
> drivers/gpu/drm/xe/xe_vm.c | 4 ++++
> drivers/gpu/drm/xe/xe_vm.h | 28 +++++++++++++++++++++++++++-
> drivers/gpu/drm/xe/xe_vm_types.h | 6 ++++++
> 4 files changed, 50 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_eudebug.c
> b/drivers/gpu/drm/xe/xe_eudebug.c
> index 9d87df75348b..8b29192ab110 100644
> --- a/drivers/gpu/drm/xe/xe_eudebug.c
> +++ b/drivers/gpu/drm/xe/xe_eudebug.c
> @@ -3074,6 +3074,19 @@ static int xe_eudebug_vma_access(struct xe_vma
> *vma, u64 offset_in_vma,
AFAICT all across the core mm code, unsigned long is used for mm
offsets, rather than u64, which we use for gpu- and physical offsets.
> xe_bo_put(bo);
>
> return ret;
> + } else if (xe_vma_is_userptr(vma)) {
> + struct xe_userptr *userptr = &to_userptr_vma(vma)-
> >userptr;
> +
> + /*
> + * XXX: access_remote_vm() would fit as userptr
> notifier has
> + * mm ref so we would not need to carry task ref at
> all.
> + * But access_remote_vm is not exported.
> access_process_vm()
> + * is exported so use it instead.
> + */
Could we add a follow-up patch that exports access_remote_vm() and
changes this code to use access_remote_vm() instead?
> + return access_process_vm(userptr->eudebug.task,
> + xe_vma_userptr(vma) +
> offset_in_vma,
> + buf, bytes,
> + write ? FOLL_WRITE : 0);
> }
>
> return -EINVAL;
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 1cb21325d8dd..235ae2db5188 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -999,6 +999,8 @@ static struct xe_vma *xe_vma_create(struct xe_vm
> *vm,
> }
>
> userptr->notifier_seq = LONG_MAX;
> +
> + xe_eudebug_track_userptr_task(userptr);
> }
>
> xe_vm_get(vm);
> @@ -1023,6 +1025,8 @@ static void xe_vma_destroy_late(struct xe_vma
> *vma)
> if (userptr->sg)
> xe_hmm_userptr_free_sg(uvma);
>
> + xe_eudebug_untrack_userptr_task(userptr);
> +
> /*
> * Since userptr pages are not pinned, we can't
> remove
> * the notifer until we're sure the GPU is not
> accessing
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index 23adb7442881..4334cf2b0d9d 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -274,9 +274,35 @@ static inline void vm_dbg(const struct
> drm_device *dev,
> const char *format, ...)
> { /* noop */ }
> #endif
> -#endif
>
> struct xe_vm_snapshot *xe_vm_snapshot_capture(struct xe_vm *vm);
> void xe_vm_snapshot_capture_delayed(struct xe_vm_snapshot *snap);
> void xe_vm_snapshot_print(struct xe_vm_snapshot *snap, struct
> drm_printer *p);
> void xe_vm_snapshot_free(struct xe_vm_snapshot *snap);
> +
> +#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
> +static inline void xe_eudebug_track_userptr_task(struct xe_userptr
> *userptr)
> +{
> + /*
> + * We could use the mm which is on notifier. But
> + * the access_remote_vm() is not exported. Thus
> + * we get reference to task for access_process_vm()
> + */
> + userptr->eudebug.task = get_task_struct(current);
> +}
> +
> +static inline void xe_eudebug_untrack_userptr_task(struct xe_userptr
> *userptr)
> +{
> + put_task_struct(userptr->eudebug.task);
> +}
> +#else
> +static inline void xe_eudebug_track_userptr_task(struct xe_userptr
> *userptr)
> +{
> +}
> +
> +static inline void xe_eudebug_untrack_userptr_task(struct xe_userptr
> *userptr)
> +{
> +}
> +#endif /* CONFIG_DRM_XE_EUDEBUG */
> +
> +#endif
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h
> b/drivers/gpu/drm/xe/xe_vm_types.h
> index 557b047ebdd7..26176ccbcbbc 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -68,6 +68,12 @@ struct xe_userptr {
> #if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
> u32 divisor;
> #endif
> +
> +#if IS_ENABLED(CONFIG_DRM_XE_EUDEBUG)
> + struct {
> + struct task_struct *task;
> + } eudebug;
> +#endif
> };
>
> struct xe_vma {
Otherwise LGTM.
Thanks,
Thomas
