Re: [PATCH 11/14] drm/amdgpu/ih6.0: Use MMIO ACK for retry CAM on IH 6.0

["Lazar, Lijo" <lijo.lazar@amd.com>]

On 04-Jul-26 12:20 AM, Timur Kristóf wrote:
> On 2026. július 3., péntek 20:11:59 közép-európai nyári idő Joshi, Mukul
> wrote:
>>> I still haven't found any explanation why we use a doorbell for the CAM in
>>> the first
>> place? Lijo, Alex, Felix does anybody know that?
>>>
>>
>> If I remember correctly, we weren't sure if the IH_RETRY_CAM_ACK register
>> would be available under
>> virtualization. And we were sure doorbells would
>> work for both bare-metal and virtualization.
> 
> Hi Mukul,
> 
> Can you clarify that please?
> 
> How are retry faults supposed to work under virtualization? Is the interrupt
> processed by the guest or the host? Why is the IH_RETRY_CAM_ACK register not
> available under virtualization?
> 

For clarification - CAM entries are separate for PF/VF. ACK register 
also has PF/VF copies. However, in general host driver imposes MMIO 
register access restrictions to VF, possibly that's the reason.

Please note that IH_RETRY_INT_CAM_CNTL is PF only. With new versions, 
please make sure to add a VF check for programming.

Thanks,
Lijo

> Thanks & best regards,
> Timur
> 
> 
>