[GIT PULL] KVM/riscv fixes for 5.19, take #2

[Paolo Bonzini]

On 7/13/22 09:17, Anup Patel wrote:
> On Wed, Jul 13, 2022 at 11:30 AM Paolo Bonzini <pbonzini at redhat.com> wrote:
>>
>> On 7/13/22 07:47, Anup Patel wrote:
>>> Hi Paolo,
>>>
>>> We have two more fixes for 5.19 which were discovered recently:
>>> 1) Fix missing PAGE_PFN_MASK
>>> 2) Fix SRCU deadlock caused by kvm_riscv_check_vcpu_requests()
>>
>> Pulled, thanks.
>>
>> For the latter, my suggestion is to remove KVM_REQ_SLEEP completely and
>> key the waiting on kvm_arch_vcpu_runnable using kvm_vcpu_halt or
>> kvm_vcpu_block.
> 
> We are using KVM_REQ_SLEEP for VCPU hotplug. The secondary
> VCPUs will block until woken-up by using an SBI call from other VCPU.
> This is different from blocking on WFI where VCPU will wake-up upon
> any interrupt.

Yes, I understand.  The idea is to have something like

	if (kvm_arch_vcpu_runnable())
		vcpu_enter_guest(vcpu);
	else
		kvm_vcpu_block(vcpu);

instead of using KVM_REQ_SLEEP to enter the blocking loop.  This works 
for both WFI and hotplug, the only difference between the two cases is 
the event that changes kvm_arch_vcpu_runnable() to true.

Paolo

> I agree with your suggestion, we should definitely use kvm_vcpu_block()
> here.
> 
>>
>> Also, I only had a quick look but it seems like vcpu->arch.pause is
>> never written?
> 
> Yes, the vcpu->arch.pause is redundant. I will remove it.
> 
>>
>> Paolo
>>
> 
> Thanks,
> Anup
>