linux-kernel - Re: [PATCH drm-misc-next v6 4/6] drm/gpuvm: track/lock/validate external/evicted objects

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Message-ID: <d586d845-fcb1-4ebc-b75d-3f147837c917@redhat.com>
Date:   Fri, 13 Oct 2023 14:05:11 +0200
From:   Danilo Krummrich <dakr@...hat.com>
To:     Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>, airlied@...il.com,
        daniel@...ll.ch, matthew.brost@...el.com, sarah.walker@...tec.com,
        donald.robson@...tec.com, boris.brezillon@...labora.com,
        christian.koenig@....com, faith@...strand.net
Cc:     dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-misc-next v6 4/6] drm/gpuvm: track/lock/validate
 external/evicted objects

On 10/10/23 08:40, Thomas Hellström wrote:
> 
> On 10/9/23 01:32, Danilo Krummrich wrote:
>> Currently the DRM GPUVM offers common infrastructure to track GPU VA
>> allocations and mappings, generically connect GPU VA mappings to their
>> backing buffers and perform more complex mapping operations on the GPU VA
>> space.
>>
>> However, there are more design patterns commonly used by drivers, which
>> can potentially be generalized in order to make the DRM GPUVM represent
>> a basis for GPU-VM implementations. In this context, this patch aims
>> at generalizing the following elements.
>>
>> 1) Provide a common dma-resv for GEM objects not being used outside of
>>     this GPU-VM.
>>
>> 2) Provide tracking of external GEM objects (GEM objects which are
>>     shared with other GPU-VMs).
>>
>> 3) Provide functions to efficiently lock all GEM objects dma-resv the
>>     GPU-VM contains mappings of.
>>
>> 4) Provide tracking of evicted GEM objects the GPU-VM contains mappings
>>     of, such that validation of evicted GEM objects is accelerated.
>>
>> 5) Provide some convinience functions for common patterns.
>>
>> Big thanks to Boris Brezillon for his help to figure out locking for
>> drivers updating the GPU VA space within the fence signalling path.
>>
>> Suggested-by: Matthew Brost <matthew.brost@...el.com>
>> Signed-off-by: Danilo Krummrich <dakr@...hat.com>
>>
>> +/**
>> + * drm_gpuvm_resv_add_fence - add fence to private and all extobj
>> + * dma-resv
>> + * @gpuvm: the &drm_gpuvm to add a fence to
>> + * @exec: the &drm_exec locking context
>> + * @fence: fence to add
>> + * @private_usage: private dma-resv usage
>> + * @extobj_usage: extobj dma-resv usage
>> + */
>> +void
>> +drm_gpuvm_resv_add_fence(struct drm_gpuvm *gpuvm,
>> +             struct drm_exec *exec,
>> +             struct dma_fence *fence,
>> +             enum dma_resv_usage private_usage,
>> +             enum dma_resv_usage extobj_usage)
>> +{
>> +    struct drm_gem_object *obj;
>> +    unsigned long index;
>> +
>> +    drm_exec_for_each_locked_object(exec, index, obj) {
>> +        dma_resv_assert_held(obj->resv);
>> +        dma_resv_add_fence(obj->resv, fence,
>> +                   drm_gpuvm_is_extobj(gpuvm, obj) ?
>> +                   private_usage : extobj_usage);
> 
> It looks like private_usage and extobj_usage are mixed up above?

Good catch, will fix.

> 
> 
>> +    }
>> +}
>> +EXPORT_SYMBOL_GPL(drm_gpuvm_resv_add_fence);
>> +
> 
> Thanks,
> 
> Thomas
> 
>