Re: [PATCH v7 5/8] drm/nouveau: Use hmm_range_fault_unlocked_timeout() for SVM faults

[Jason Gunthorpe]

On Tue, Jul 07, 2026 at 12:47:22PM -0700, Stanislav Kinsburskii wrote:
> nouveau_range_fault() takes mmap_read_lock() only to call
> hmm_range_fault(). It also keeps a single HMM_RANGE_DEFAULT_TIMEOUT
> deadline across both HMM -EBUSY retries and post-fault
> mmu_interval_read_retry() retries.
> 
> Use hmm_range_fault_unlocked_timeout() instead. The HMM helper now owns
> the mmap lock and refreshes range->notifier_seq for its internal retries.
> Nouveau keeps its existing absolute deadline in the outer loop and passes
> the remaining jiffies to the helper for each fault attempt, so retries
> caused by mmu_interval_read_retry() do not reset the overall retry budget.
> 
> Nouveau still validates the interval notifier sequence while holding
> svmm->mutex before programming the GPU mapping.
> 
> Signed-off-by: Stanislav Kinsburskii <skinsburskii@xxxxxxxxx>
> ---
>  drivers/gpu/drm/nouveau/nouveau_svm.c |   11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

> -		range.notifier_seq = mmu_interval_read_begin(range.notifier);
> -		mmap_read_lock(mm);
> -		ret = hmm_range_fault(&range);
> -		mmap_read_unlock(mm);
> -		if (ret) {
> -			if (ret == -EBUSY)
> -				continue;
> +		ret = hmm_range_fault_unlocked_timeout(&range,
> +				       max_t(long, timeout - jiffies, 1UL));

Avoid max_t, 1L should be a signed long.

Though I'm even more concerned about the timeout if drivers are now
wrapping the whole thing in a timeout... That's not sensible at all

Jason