Re: [PATCH] PPC: KVM: fix VCPU run for HV KVM

From: Alexey Kardashevskiy
Date: Tue Feb 04 2014 - 03:03:37 EST


On 01/13/2014 02:44 AM, Alexander Graf wrote:
>
> On 10.01.2014, at 08:21, Alexey Kardashevskiy <aik@xxxxxxxxx> wrote:
>
>> When write to MMIO happens and there is an ioeventfd for that and
>> is handled successfully, ioeventfd_write() returns 0 (success) and
>> kvmppc_handle_store() returns EMULATE_DONE. Then kvmppc_emulate_mmio()
>> converts EMULATE_DONE to RESUME_GUEST_NV and this broke from the loop.
>>
>> This adds handling of RESUME_GUEST_NV in kvmppc_vcpu_run_hv().
>>
>> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
>> Suggested-by: Paul Mackerras <paulus@xxxxxxxxx>
>> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
>> ---
>>
>> This definitely needs a better commit message. Please, help.
>> ps. it seems like ioeventfd never worked on ppc64. hm.
>>
>> ---
>> arch/powerpc/kvm/book3s_hv.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index 072287f..24f363f 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -1569,7 +1569,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu)
>> vcpu->arch.fault_dar, vcpu->arch.fault_dsisr);
>> srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
>> }
>> - } while (r == RESUME_GUEST);
>> + } while ((r == RESUME_GUEST_NV) || (r == RESUME_GUEST));
>
> How about
>
> while(!(r & RESUME_FLAG_HOST));


Rather "while(!(r & RESUME_FLAG_HOST) && (r > 0));" and still not obvious
that this is really better.

Paul agrees with the original patch (and made a better commit message for
our internal tree) but I just cannot make him reply in this thread, keep
constantly asking him but to no avail :)


> That should cover all RESUME_GUEST_XXX cases just fine. Apart from that
> I agree that we should check for ! FLAG_HOST bit rather than the actual
> RESUME_GUEST value in all case where we check for it (read: please
> update all places).

There are 3 places remotely similar to this and none of them requires a fix
like above.



--
Alexey
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