[PATCH 1/2] drm/xe/pf: Limit fair VF LMEM provisioning

[Cavitt, Jonathan]

-----Original Message-----
From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Michal Wajdeczko
Sent: Thursday, July 11, 2024 12:23 PM
To: intel-xe at lists.freedesktop.org
Cc: Wajdeczko, Michal <Michal.Wajdeczko at intel.com>
Subject: [PATCH 1/2] drm/xe/pf: Limit fair VF LMEM provisioning
> 
> Due to the current design of the BO and VRAM manager, any object
> with XE_BO_FLAG_PINNED flag, which the PF driver uses during VF
> LMEM provisionining, is created with the TTM_PL_FLAG_CONTIGUOUS
> flag, which may cause VRAM fragmentation that prevents subsequent
> allocations of larger objects, like fair VF LMEM provisioning.
> 
> To avoid such failures, round down fair VF LMEM provisioning size
> to next power of two size, to compensate what xe_ttm_vram_mgr is
> doing to achieve contiguous allocations.
> 
> Fixes: ac6598aed1b3 ("drm/xe/pf: Add support to configure SR-IOV VFs")
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> index db6c213da847..4699b7836001 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> @@ -1543,6 +1543,7 @@ static u64 pf_estimate_fair_lmem(struct xe_gt *gt, unsigned int num_vfs)
>  	u64 fair;
>  
>  	fair = div_u64(available, num_vfs);
> +	fair = rounddown_pow_of_two(fair);	/* XXX: ttm_vram_mgr & drm_buddy limitation */
>  	fair = ALIGN_DOWN(fair, alignment);

If the alignment is also a power of two, then ALIGN_DOWN here probably
isn't necessary.  But I won't block on it because I'm probably just
misunderstanding something.

Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
-Jonathan Cavitt

>  #ifdef MAX_FAIR_LMEM
>  	fair = min_t(u64, MAX_FAIR_LMEM, fair);
> -- 
> 2.43.0
> 
>