Re: [PATCH v7 3/4] KVM: arm64: Dirty quota-based throttling of vcpus

[Shivam Kumar <shivam.kumar1@nutanix.com>]

On 15/11/22 5:57 am, Yunhong Jiang wrote:
> On Sun, Nov 13, 2022 at 05:05:10PM +0000, Shivam Kumar wrote:
>> Exit to userspace whenever the dirty quota is exhausted (i.e. dirty count
>> equals/exceeds dirty quota) to request more dirty quota.
>>
>> Suggested-by: Shaju Abraham <shaju.abraham@nutanix.com>
>> Suggested-by: Manish Mishra <manish.mishra@nutanix.com>
>> Co-developed-by: Anurag Madnawat <anurag.madnawat@nutanix.com>
>> Signed-off-by: Anurag Madnawat <anurag.madnawat@nutanix.com>
>> Signed-off-by: Shivam Kumar <shivam.kumar1@nutanix.com>
>> ---
>>   arch/arm64/kvm/arm.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 94d33e296e10..850024982dd9 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -746,6 +746,15 @@ static int check_vcpu_requests(struct kvm_vcpu *vcpu)
>>   
>>   		if (kvm_check_request(KVM_REQ_SUSPEND, vcpu))
>>   			return kvm_vcpu_suspend(vcpu);
>> +
>> +		if (kvm_check_request(KVM_REQ_DIRTY_QUOTA_EXIT, vcpu)) {
>> +			struct kvm_run *run = vcpu->run;
>> +
>> +			run->exit_reason = KVM_EXIT_DIRTY_QUOTA_EXHAUSTED;
>> +			run->dirty_quota_exit.count = vcpu->stat.generic.pages_dirtied;
>> +			run->dirty_quota_exit.quota = vcpu->dirty_quota;
>> +			return 0;
>> +		}
> There is a recheck on x86 side, but not here. Any architecture specific reason?
> Sorry if I missed anything.
> 
> BTW, not sure if the x86/arm code can be combined into a common function. I
> don't see any architecture specific code here.
Yes, I think we may use a common function for x86/arm.

With that, this would look like:

if (kvm_check_dirty_quota_request(vcpu)) {
	return 0;
}

Thanks,
Shivam