[PATCH] drm/amdgpu: drop kiq access while in reset

[Lazar, Lijo]

On 6/24/2024 5:19 PM, Christian König wrote:
> Am 24.06.24 um 11:52 schrieb Lazar, Lijo:
>>
>> On 6/24/2024 3:08 PM, Christian König wrote:
>>> Am 24.06.24 um 08:34 schrieb Lazar, Lijo:
>>>> On 6/24/2024 12:01 PM, Vignesh Chander wrote:
>>>>> correctly handle the case when trylock fails when gpu is
>>>>> about to be reset by dropping the request instead of using mmio
>>>>>
>>>>> Signed-off-by: Vignesh Chander <Vignesh.Chander at amd.com>
>>>> Reviewed-by: Lijo Lazar <lijo.lazar at amd.com>
>>>>
>>>> Thanks,
>>>> Lijo
>>>>
>>>>> ---
>>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 38
>>>>> ++++++++++++----------
>>>>>    1 file changed, 21 insertions(+), 17 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> index a7ce8280b17ce7..3cfd24699d691d 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> @@ -613,10 +613,11 @@ uint32_t amdgpu_device_rreg(struct
>>>>> amdgpu_device *adev,
>>>>>          if ((reg * 4) < adev->rmmio_size) {
>>>>>            if (!(acc_flags & AMDGPU_REGS_NO_KIQ) &&
>>>>> -            amdgpu_sriov_runtime(adev) &&
>>>>> -            down_read_trylock(&adev->reset_domain->sem)) {
>>>>> -            ret = amdgpu_kiq_rreg(adev, reg, 0);
>>>>> -            up_read(&adev->reset_domain->sem);
>>>>> +            amdgpu_sriov_runtime(adev) {
>>>>> +            if (down_read_trylock(&adev->reset_domain->sem)) {
>>>>> +                ret = amdgpu_kiq_rreg(adev, reg, 0);
>>>>> +                up_read(&adev->reset_domain->sem);
>>>>> +            }
>>> What has actually changed here? As far as I can see that isn't
>>> functionally different to the existing code.
>>>
>> In earlier logic, if it fails to get the lock, it takes the 'else' path.
>> The 'else' path is not meant for sriov/vf.
> 
> Yeah, but the read or write is then just silently dropped.
> 
> That can't be correct either.
> 

These are void funcs. Moreover, the drops will happen if there is
concurrent access from another thread while a reset is going on. That is
expected and those accesses during a reset won't help anyway.

Thanks,
Lijo

> Regards,
> Christian.
> 
>>
>> Thanks,
>> Lijo
>>
>>> Regards,
>>> Christian.
>>>
>>>>>            } else {
>>>>>                ret = readl(((void __iomem *)adev->rmmio) + (reg * 4));
>>>>>            }
>>>>> @@ -681,10 +682,11 @@ uint32_t amdgpu_device_xcc_rreg(struct
>>>>> amdgpu_device *adev,
>>>>>                                 &rlcg_flag)) {
>>>>>                ret = amdgpu_virt_rlcg_reg_rw(adev, reg, 0, rlcg_flag,
>>>>> GET_INST(GC, xcc_id));
>>>>>            } else if (!(acc_flags & AMDGPU_REGS_NO_KIQ) &&
>>>>> -            amdgpu_sriov_runtime(adev) &&
>>>>> -            down_read_trylock(&adev->reset_domain->sem)) {
>>>>> -            ret = amdgpu_kiq_rreg(adev, reg, xcc_id);
>>>>> -            up_read(&adev->reset_domain->sem);
>>>>> +            amdgpu_sriov_runtime(adev) {
>>>>> +            if (down_read_trylock(&adev->reset_domain->sem)) {
>>>>> +                ret = amdgpu_kiq_rreg(adev, reg, xcc_id);
>>>>> +                up_read(&adev->reset_domain->sem);
>>>>> +            }
>>>>>            } else {
>>>>>                ret = readl(((void __iomem *)adev->rmmio) + (reg * 4));
>>>>>            }
>>>>> @@ -740,10 +742,11 @@ void amdgpu_device_wreg(struct amdgpu_device
>>>>> *adev,
>>>>>          if ((reg * 4) < adev->rmmio_size) {
>>>>>            if (!(acc_flags & AMDGPU_REGS_NO_KIQ) &&
>>>>> -            amdgpu_sriov_runtime(adev) &&
>>>>> -            down_read_trylock(&adev->reset_domain->sem)) {
>>>>> -            amdgpu_kiq_wreg(adev, reg, v, 0);
>>>>> -            up_read(&adev->reset_domain->sem);
>>>>> +            amdgpu_sriov_runtime(adev) {
>>>>> +            if (down_read_trylock(&adev->reset_domain->sem)) {
>>>>> +                amdgpu_kiq_wreg(adev, reg, v, 0);
>>>>> +                up_read(&adev->reset_domain->sem);
>>>>> +            }
>>>>>            } else {
>>>>>                writel(v, ((void __iomem *)adev->rmmio) + (reg * 4));
>>>>>            }
>>>>> @@ -812,11 +815,12 @@ void amdgpu_device_xcc_wreg(struct
>>>>> amdgpu_device *adev,
>>>>>                                 &rlcg_flag)) {
>>>>>                amdgpu_virt_rlcg_reg_rw(adev, reg, v, rlcg_flag,
>>>>> GET_INST(GC, xcc_id));
>>>>>            } else if (!(acc_flags & AMDGPU_REGS_NO_KIQ) &&
>>>>> -            amdgpu_sriov_runtime(adev) &&
>>>>> -            down_read_trylock(&adev->reset_domain->sem)) {
>>>>> -            amdgpu_kiq_wreg(adev, reg, v, xcc_id);
>>>>> -            up_read(&adev->reset_domain->sem);
>>>>> -        } else {
>>>>> +            amdgpu_sriov_runtime(adev) {
>>>>> +            if (down_read_trylock(&adev->reset_domain->sem)) {
>>>>> +                amdgpu_kiq_wreg(adev, reg, v, xcc_id);
>>>>> +                up_read(&adev->reset_domain->sem);
>>>>> +            }
>>>>> +            } else {
>>>>>                writel(v, ((void __iomem *)adev->rmmio) + (reg * 4));
>>>>>            }
>>>>>        } else {
>