Re: [PATCH v7 8/8] drm/gpusvm: Use hmm_range_fault_unlocked_timeout() for range faults

[Jason Gunthorpe]

On Tue, Jul 07, 2026 at 12:47:43PM -0700, Stanislav Kinsburskii wrote:
> Several GPU SVM paths take mmap_read_lock() only to call hmm_range_fault(),
> then retry -EBUSY until HMM_RANGE_DEFAULT_TIMEOUT expires. Those paths use
> MMU interval notifiers whose mm matches the mm that was locked for the HMM
> fault.
> 
> Use hmm_range_fault_unlocked_timeout() for those faults and pass the
> remaining retry budget to HMM. The helper owns mmap_lock acquisition and
> refreshes range->notifier_seq internally for each retry, while GPU SVM
> keeps its existing driver-lock validation with mmu_interval_read_retry()
> after a successful fault.
> 
> Leave drm_gpusvm_check_pages() on hmm_range_fault() because that path is
> called with the mmap lock already held by its caller.
> 
> Signed-off-by: Stanislav Kinsburskii <skinsburskii@xxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_gpusvm.c |   52 ++++++------------------------------------
>  1 file changed, 7 insertions(+), 45 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

> -	mmap_read_unlock(range->gpusvm->mm);
> +	err = hmm_range_fault_unlocked_timeout(&hmm_range,
> +				max_t(long, timeout - jiffies, 1));

Same remark about max_t

Jason