[Intel-gfx] [RFC PATCH 16/97] drm/i915/guc: Start protecting access to CTB descriptors

[Michal Wajdeczko]

On 25.05.2021 05:21, Matthew Brost wrote:
> On Thu, May 06, 2021 at 12:13:30PM -0700, Matthew Brost wrote:
>> From: Michal Wajdeczko <michal.wajdeczko at intel.com>
>>
>> We want to stop using guc.send_mutex while sending CTB messages
>> so we have to start protecting access to CTB send descriptor.
>>
>> For completeness protect also CTB send descriptor.
> 
> Michal I think you have a typo here, receive descriptor, right? Again

oops, yes, it's typo

> this is going to get squashed in the firmware update patch but thought
> I'd mention this.

again, please don't squash patches if not necessary

> 
> With that:
> Reviewed-by: Matthew Brost <matthew.brost at intel.com> 
> 
>>
>> Add spinlock to struct intel_guc_ct_buffer and start using it.
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
>> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
>> ---
>>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 14 ++++++++++++--
>>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h |  2 ++
>>  2 files changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> index a4b2e7fe318b..bee0958d8bae 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> @@ -89,6 +89,8 @@ static void ct_incoming_request_worker_func(struct work_struct *w);
>>   */
>>  void intel_guc_ct_init_early(struct intel_guc_ct *ct)
>>  {
>> +	spin_lock_init(&ct->ctbs.send.lock);
>> +	spin_lock_init(&ct->ctbs.recv.lock);
>>  	spin_lock_init(&ct->requests.lock);
>>  	INIT_LIST_HEAD(&ct->requests.pending);
>>  	INIT_LIST_HEAD(&ct->requests.incoming);
>> @@ -479,17 +481,22 @@ static int ct_send(struct intel_guc_ct *ct,
>>  	GEM_BUG_ON(len & ~GUC_CT_MSG_LEN_MASK);
>>  	GEM_BUG_ON(!response_buf && response_buf_size);
>>  
>> +	spin_lock_irqsave(&ct->ctbs.send.lock, flags);
>> +
>>  	fence = ct_get_next_fence(ct);
>>  	request.fence = fence;
>>  	request.status = 0;
>>  	request.response_len = response_buf_size;
>>  	request.response_buf = response_buf;
>>  
>> -	spin_lock_irqsave(&ct->requests.lock, flags);
>> +	spin_lock(&ct->requests.lock);
>>  	list_add_tail(&request.link, &ct->requests.pending);
>> -	spin_unlock_irqrestore(&ct->requests.lock, flags);
>> +	spin_unlock(&ct->requests.lock);
>>  
>>  	err = ct_write(ct, action, len, fence);
>> +
>> +	spin_unlock_irqrestore(&ct->ctbs.send.lock, flags);
>> +
>>  	if (unlikely(err))
>>  		goto unlink;
>>  
>> @@ -825,6 +832,7 @@ static int ct_handle_request(struct intel_guc_ct *ct, const u32 *msg)
>>  void intel_guc_ct_event_handler(struct intel_guc_ct *ct)
>>  {
>>  	u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */
>> +	unsigned long flags;
>>  	int err = 0;
>>  
>>  	if (unlikely(!ct->enabled)) {
>> @@ -833,7 +841,9 @@ void intel_guc_ct_event_handler(struct intel_guc_ct *ct)
>>  	}
>>  
>>  	do {
>> +		spin_lock_irqsave(&ct->ctbs.recv.lock, flags);
>>  		err = ct_read(ct, msg);
>> +		spin_unlock_irqrestore(&ct->ctbs.recv.lock, flags);
>>  		if (err)
>>  			break;
>>  
>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
>> index fc9486779e87..bc52dc479a14 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
>> @@ -27,11 +27,13 @@ struct intel_guc;
>>   * record (command transport buffer descriptor) and the actual buffer which
>>   * holds the commands.
>>   *
>> + * @lock: protects access to the commands buffer and buffer descriptor
>>   * @desc: pointer to the buffer descriptor
>>   * @cmds: pointer to the commands buffer
>>   * @size: size of the commands buffer
>>   */
>>  struct intel_guc_ct_buffer {
>> +	spinlock_t lock;
>>  	struct guc_ct_buffer_desc *desc;
>>  	u32 *cmds;
>>  	u32 size;
>> -- 
>> 2.28.0
>>
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