Re: [Intel-gfx] [PATCH v3 2/2] drm/i915/gt: Serialize TLB invalidates with GT resets

[Andrzej Hajda]

On 04.07.2022 10:09, Mauro Carvalho Chehab wrote:
> From: Chris Wilson <chris.p.wilson@xxxxxxxxx>
>
> Avoid trying to invalidate the TLB in the middle of performing an
> engine reset, as this may result in the reset timing out. Currently,
> the TLB invalidate is only serialised by its own mutex, forgoing the
> uncore lock, but we can take the uncore->lock as well to serialise
> the mmio access, thereby serialising with the GDRST.
>
> Tested on a NUC5i7RYB, BIOS RYBDWi35.86A.0380.2019.0517.1530 with
> i915 selftest/hangcheck.
>
> Cc: stable@xxxxxxxxxxxxxxx # Up to 4.4
> Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
> Reported-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Tested-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Cc: Chris Wilson <chris.p.wilson@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Cc: Andi Shyti <andi.shyti@xxxxxxxxx>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>

Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>

Regards
Andrzej

> ---
>
> To avoid mailbombing on a large number of people, only mailing lists were C/C on the cover.
> See [PATCH v3 0/2] at: https://lore.kernel.org/all/cover.1656921701.git.mchehab@xxxxxxxxxx/
>
>   drivers/gpu/drm/i915/gt/intel_gt.c | 15 ++++++++++++++-
>   1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 8da3314bb6bf..68c2b0d8f187 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -952,6 +952,20 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   	mutex_lock(&gt->tlb_invalidate_lock);
>   	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
>   
> +	spin_lock_irq(&uncore->lock); /* serialise invalidate with GT reset */
> +
> +	for_each_engine(engine, gt, id) {
> +		struct reg_and_bit rb;
> +
> +		rb = get_reg_and_bit(engine, regs == gen8_regs, regs, num);
> +		if (!i915_mmio_reg_offset(rb.reg))
> +			continue;
> +
> +		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
> +	}
> +
> +	spin_unlock_irq(&uncore->lock);
> +
>   	for_each_engine(engine, gt, id) {
>   		/*
>   		 * HW architecture suggest typical invalidation time at 40us,
> @@ -966,7 +980,6 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
>   		if (!i915_mmio_reg_offset(rb.reg))
>   			continue;
>   
> -		intel_uncore_write_fw(uncore, rb.reg, rb.bit);
>   		if (__intel_wait_for_register_fw(uncore,
>   						 rb.reg, rb.bit, 0,
>   						 timeout_us, timeout_ms,