[PATCH 3/3] drm/amdgpu/mes11: make fence waits synchronous
Liu, Shaoyun
Shaoyun.Liu at amd.com
Thu Apr 18 14:42:09 UTC 2024
[AMD Official Use Only - General]
I think the only user for the MES is kernel driver and all the submission to MES need to be synced , driver already have the mes->ring_lock to ensure that . I don't know why there is a necessary to use separate fence per request .
MES do update the API status for each API (update the fence seq at an specific address) , but driver can decide to check it or not . For now , MES don't generate a interrupt as fence signal, but from driver side it can check the fence seq as polling .
Regards
Shaoyun.liu
-----Original Message-----
From: Koenig, Christian <Christian.Koenig at amd.com>
Sent: Thursday, April 18, 2024 1:59 AM
To: Alex Deucher <alexdeucher at gmail.com>; Liu, Shaoyun <Shaoyun.Liu at amd.com>
Cc: Chen, Horace <Horace.Chen at amd.com>; amd-gfx at lists.freedesktop.org; Andrey Grodzovsky <Andrey.Grodzovsky at amd.com>; Kuehling, Felix <Felix.Kuehling at amd.com>; Deucher, Alexander <Alexander.Deucher at amd.com>; Xiao, Jack <Jack.Xiao at amd.com>; Zhang, Hawking <Hawking.Zhang at amd.com>; Liu, Monk <Monk.Liu at amd.com>; Xu, Feifei <Feifei.Xu at amd.com>; Chang, HaiJun <HaiJun.Chang at amd.com>; Leo Liu <leo.liiu at amd.com>; Liu, Jenny (Jing) <Jenny-Jing.Liu at amd.com>
Subject: Re: [PATCH 3/3] drm/amdgpu/mes11: make fence waits synchronous
Am 17.04.24 um 21:21 schrieb Alex Deucher:
> On Wed, Apr 17, 2024 at 3:17 PM Liu, Shaoyun <Shaoyun.Liu at amd.com> wrote:
>> [AMD Official Use Only - General]
>>
>> I have a discussion with Christian about this before . The
>> conclusion is that driver should prevent multiple process from using
>> the MES ring at the same time . Also for current MES ring usage
>> ,driver doesn't have the logic to prevent the ring been overflowed
>> and we doesn't hit the issue because MES will wait polling for each
>> MES submission . If we want to change the MES to work asynchronously
>> , we need to consider a way to avoid this (similar to add the limit
>> in the fence handling we use for kiq and HMM paging)
>>
> I think we need a separate fence (different GPU address and seq
> number) per request. Then each caller can wait independently.
Well no, we need to modify the MES firmware to stop abusing the fence as signaling mechanism for the result of an operation.
I've pointed that out before and I think this is a hard requirement for correct operation.
Additional to that retrying on the reset flag looks like another broken workaround to me.
So just to make it clear this approach is a NAK from my side, don't commit that.
Regards,
Christian.
>
> Alex
>
>> Regards
>> Shaoyun.liu
>>
>> -----Original Message-----
>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>> Christian König
>> Sent: Wednesday, April 17, 2024 8:49 AM
>> To: Chen, Horace <Horace.Chen at amd.com>; amd-gfx at lists.freedesktop.org
>> Cc: Andrey Grodzovsky <Andrey.Grodzovsky at amd.com>; Kuehling, Felix
>> <Felix.Kuehling at amd.com>; Deucher, Alexander
>> <Alexander.Deucher at amd.com>; Xiao, Jack <Jack.Xiao at amd.com>; Zhang,
>> Hawking <Hawking.Zhang at amd.com>; Liu, Monk <Monk.Liu at amd.com>; Xu,
>> Feifei <Feifei.Xu at amd.com>; Chang, HaiJun <HaiJun.Chang at amd.com>; Leo
>> Liu <leo.liiu at amd.com>; Liu, Jenny (Jing) <Jenny-Jing.Liu at amd.com>
>> Subject: Re: [PATCH 3/3] drm/amdgpu/mes11: make fence waits
>> synchronous
>>
>> Am 17.04.24 um 13:30 schrieb Horace Chen:
>>> The MES firmware expects synchronous operation with the driver. For
>>> this to work asynchronously, each caller would need to provide its
>>> own fence location and sequence number.
>> Well that's certainly not correct. The seqno takes care that we can wait async for the submission to complete.
>>
>> So clear NAK for that patch here.
>>
>> Regards,
>> Christian.
>>
>>> For now, add a mutex lock to serialize the MES submission.
>>> For SR-IOV long-wait case, break the long-wait to separated part to
>>> prevent this wait from impacting reset sequence.
>>>
>>> Signed-off-by: Horace Chen <horace.chen at amd.com>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c | 3 +++
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h | 1 +
>>> drivers/gpu/drm/amd/amdgpu/mes_v11_0.c | 18 ++++++++++++++----
>>> 3 files changed, 18 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
>>> index 78e4f88f5134..8896be95b2c8 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.c
>>> @@ -137,6 +137,7 @@ int amdgpu_mes_init(struct amdgpu_device *adev)
>>> spin_lock_init(&adev->mes.queue_id_lock);
>>> spin_lock_init(&adev->mes.ring_lock);
>>> mutex_init(&adev->mes.mutex_hidden);
>>> + mutex_init(&adev->mes.submission_lock);
>>>
>>> adev->mes.total_max_queue = AMDGPU_FENCE_MES_QUEUE_ID_MASK;
>>> adev->mes.vmid_mask_mmhub = 0xffffff00; @@ -221,6 +222,7 @@
>>> int amdgpu_mes_init(struct amdgpu_device *adev)
>>> idr_destroy(&adev->mes.queue_id_idr);
>>> ida_destroy(&adev->mes.doorbell_ida);
>>> mutex_destroy(&adev->mes.mutex_hidden);
>>> + mutex_destroy(&adev->mes.submission_lock);
>>> return r;
>>> }
>>>
>>> @@ -240,6 +242,7 @@ void amdgpu_mes_fini(struct amdgpu_device *adev)
>>> idr_destroy(&adev->mes.queue_id_idr);
>>> ida_destroy(&adev->mes.doorbell_ida);
>>> mutex_destroy(&adev->mes.mutex_hidden);
>>> + mutex_destroy(&adev->mes.submission_lock);
>>> }
>>>
>>> static void amdgpu_mes_queue_free_mqd(struct amdgpu_mes_queue *q)
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
>>> index 6b3e1844eac5..90af935cc889 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mes.h
>>> @@ -85,6 +85,7 @@ struct amdgpu_mes {
>>>
>>> struct amdgpu_ring ring;
>>> spinlock_t ring_lock;
>>> + struct mutex submission_lock;
>>>
>>> const struct firmware *fw[AMDGPU_MAX_MES_PIPES];
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/mes_v11_0.c
>>> b/drivers/gpu/drm/amd/amdgpu/mes_v11_0.c
>>> index e40d00afd4f5..0a609a5b8835 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/mes_v11_0.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/mes_v11_0.c
>>> @@ -162,6 +162,7 @@ static int mes_v11_0_submit_pkt_and_poll_completion(struct amdgpu_mes *mes,
>>> struct amdgpu_ring *ring = &mes->ring;
>>> unsigned long flags;
>>> signed long timeout = adev->usec_timeout;
>>> + signed long retry_count = 1;
>>> const char *op_str, *misc_op_str;
>>>
>>> if (x_pkt->header.opcode >= MES_SCH_API_MAX) @@ -169,15
>>> +170,19 @@ static int
>>> mes_v11_0_submit_pkt_and_poll_completion(struct amdgpu_mes *mes,
>>>
>>> if (amdgpu_emu_mode) {
>>> timeout *= 100;
>>> - } else if (amdgpu_sriov_vf(adev)) {
>>> + }
>>> +
>>> + if (amdgpu_sriov_vf(adev) && timeout > 0) {
>>> /* Worst case in sriov where all other 15 VF timeout, each VF needs about 600ms */
>>> - timeout = 15 * 600 * 1000;
>>> + retry_count = (15 * 600 * 1000) / timeout;
>>> }
>>> BUG_ON(size % 4 != 0);
>>>
>>> + mutex_lock(&mes->submission_lock);
>>> spin_lock_irqsave(&mes->ring_lock, flags);
>>> if (amdgpu_ring_alloc(ring, ndw)) {
>>> spin_unlock_irqrestore(&mes->ring_lock, flags);
>>> + mutex_unlock(&mes->submission_lock);
>>> return -ENOMEM;
>>> }
>>>
>>> @@ -199,8 +204,13 @@ static int mes_v11_0_submit_pkt_and_poll_completion(struct amdgpu_mes *mes,
>>> else
>>> dev_dbg(adev->dev, "MES msg=%d was emitted\n",
>>> x_pkt->header.opcode);
>>>
>>> - r = amdgpu_fence_wait_polling(ring, ring->fence_drv.sync_seq,
>>> - timeout);
>>> + do {
>>> + r = amdgpu_fence_wait_polling(ring, ring->fence_drv.sync_seq,
>>> + timeout);
>>> + retry_count--;
>>> + } while (retry_count > 0 && !amdgpu_in_reset(adev));
>>> +
>>> + mutex_unlock(&mes->submission_lock);
>>> if (r < 1) {
>>>
>>> if (misc_op_str)
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