Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> writes:
> Hi Aneesh,
>
> Thanks for looking into this patch. My responses inline below:
>
> "Aneesh Kumar K.V (IBM)" <aneesh.kumar@xxxxxxxxxx> writes:
>
>> Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> writes:
>>
>>> From: Jordan Niethe <jniethe5@xxxxxxxxx>
>>>
>>> An L0 must invalidate the L2's RPT during H_GUEST_DELETE if this has not
>>> already been done. This is a slow operation that means H_GUEST_DELETE
>>> must return H_BUSY multiple times before completing. Invalidating the
>>> tables before deleting the guest so there is less work for the L0 to do.
>>>
>>> Signed-off-by: Jordan Niethe <jniethe5@xxxxxxxxx>
>>> ---
>>> arch/powerpc/include/asm/kvm_book3s.h | 1 +
>>> arch/powerpc/kvm/book3s_hv.c | 6 ++++--
>>> arch/powerpc/kvm/book3s_hv_nested.c | 2 +-
>>> 3 files changed, 6 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
>>> index 4f527d09c92b..a37736ed3728 100644
>>> --- a/arch/powerpc/include/asm/kvm_book3s.h
>>> +++ b/arch/powerpc/include/asm/kvm_book3s.h
>>> @@ -302,6 +302,7 @@ void kvmhv_nested_exit(void);
>>> void kvmhv_vm_nested_init(struct kvm *kvm);
>>> long kvmhv_set_partition_table(struct kvm_vcpu *vcpu);
>>> long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu);
>>> +void kvmhv_flush_lpid(u64 lpid);
>>> void kvmhv_set_ptbl_entry(u64 lpid, u64 dw0, u64 dw1);
>>> void kvmhv_release_all_nested(struct kvm *kvm);
>>> long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu);
>>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>>> index 1ed6ec140701..5543e8490cd9 100644
>>> --- a/arch/powerpc/kvm/book3s_hv.c
>>> +++ b/arch/powerpc/kvm/book3s_hv.c
>>> @@ -5691,10 +5691,12 @@ static void kvmppc_core_destroy_vm_hv(struct kvm *kvm)
>>> kvmhv_set_ptbl_entry(kvm->arch.lpid, 0, 0);
>>> }
>>>
>>> - if (kvmhv_is_nestedv2())
>>> + if (kvmhv_is_nestedv2()) {
>>> + kvmhv_flush_lpid(kvm->arch.lpid);
>>> plpar_guest_delete(0, kvm->arch.lpid);
>>>
>>
>> I am not sure I follow the optimization here. I would expect the
>> hypervisor to kill all the translation caches as part of guest_delete.
>> What is the benefit of doing a lpid flush outside the guest delete?
>>
> Thats right. However without this optimization the H_GUEST_DELETE hcall
> in plpar_guest_delete() returns H_BUSY multiple times resulting in
> multiple hcalls to the hypervisor until it finishes. Flushing the guest
> translation cache upfront reduces the number of HCALLs L1 guests has to
> make to delete a L2 guest via H_GUEST_DELETE.
>
can we add that as a comment above that kvmhv_flush_lpid()?
-aneesh
