Re: [PATCH 2/4] fixup! drm/nouveau: use hmm_range_fault_unlocked_timeout() for SVM faults

[Stanislav Kinsburskii <skinsburskii@gmail.com>]

On Tue, Jul 14, 2026 at 01:13:38PM -0700, Stanislav Kinsburskii wrote:
> nouveau_range_fault() now uses hmm_range_fault_unlocked_timeout() for
> the HMM fault path. The timeout passed to that helper is meant to bound
> HMM's internal mmu-notifier retry loop, not the whole nouveau retry loop
> around mmu_interval_read_retry().
> 
> Pass the full relative HMM_RANGE_DEFAULT_TIMEOUT value to
> hmm_range_fault_unlocked_timeout() on each attempt, and retry from the
> nouveau-side mmu_interval_read_retry() check with a fresh HMM retry
> budget. This lets HMM continue when it has made progress, while still
> preserving a timeout for repeated notifier invalidation retries inside
> one HMM fault attempt.
> 
> This also removes the open-coded absolute deadline and remaining-time
> calculation from nouveau_range_fault().
> 

Sashiko is right. I'll need to do it differently.
There will be a v2 of this series.

Thanks,
Stanislav


> Signed-off-by: Stanislav Kinsburskii <skinsburskii@gmail.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_svm.c |   30 ++++++++++--------------------
>  1 file changed, 10 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index 4cfb6eb7c771..b1415c2e49fc 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -655,8 +655,7 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
>  			       unsigned long hmm_flags,
>  			       struct svm_notifier *notifier)
>  {
> -	unsigned long timeout =
> -		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> +	unsigned long timeout = msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
>  	/* Have HMM fault pages within the fault window to the GPU. */
>  	unsigned long hmm_pfns[1];
>  	struct hmm_range range = {
> @@ -677,25 +676,16 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
>  	range.start = notifier->notifier.interval_tree.start;
>  	range.end = notifier->notifier.interval_tree.last + 1;
>  
> -	while (true) {
> -		if (time_after(jiffies, timeout)) {
> -			ret = -EBUSY;
> -			goto out;
> -		}
> -
> -		ret = hmm_range_fault_unlocked_timeout(&range,
> -						       max(timeout - jiffies,
> -							   1L));
> -		if (ret)
> -			goto out;
> +again:
> +	ret = hmm_range_fault_unlocked_timeout(&range, timeout);
> +	if (ret)
> +		goto out;
>  
> -		mutex_lock(&svmm->mutex);
> -		if (mmu_interval_read_retry(range.notifier,
> -					    range.notifier_seq)) {
> -			mutex_unlock(&svmm->mutex);
> -			continue;
> -		}
> -		break;
> +	mutex_lock(&svmm->mutex);
> +	if (mmu_interval_read_retry(range.notifier,
> +				    range.notifier_seq)) {
> +		mutex_unlock(&svmm->mutex);
> +		goto again;
>  	}
>  
>  	nouveau_hmm_convert_pfn(drm, &range, args);
> 
>