Re: [edk2-devel] [edk2-staging/RiscV64QemuVirt PATCH V7 05/20] UefiCpuPkg: Add CpuTimerDxe module

["Michael Brown" <mcb30@ipxe.org>]

On 09/02/2023 10:28, Sunil V L wrote:
>>> +  gBS->RestoreTPL (OriginalTPL);
>>> +  RiscVEnableTimerInterrupt (); // enable SMode timer int
>>> +}
>>
>> This design looks as though it does not support nested timer interrupts.
>> The call to RestoreTPL() may invoke callbacks that may themselves include
>> delay loops that wait upon further timer interrupts.  With the above code,
>> those timer interrupts will never arrive since the timer interrupt is
>> disabled at the point that you call RestoreTPL().
>>
>> This will break device drivers such as those for USB network devices that
>> rely on nested timer interrupts.
> 
> Thanks a lot for this feedback and background. We are aware of few issues
> in this module. Currently, it is mostly porting what exists today in
> edk2-platforms repo. We want to add all these additional fixes after
> this basic thing is merged. That way we will have git history instead of
> combining all fixes single commit. Andrei has a patch ready and waiting
> for this to get merged. We can either combine this with his patch or
> create one more.
> 
> Would that strategy be fine with you?

Sure, as long as someone other than me is keeping track of the need to 
fix this bug.  My work here is done.  :)

Thanks,

Michael