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

On 01/13/2014 02:44 AM, Alexander Graf wrote:

On 10.01.2014, at 08:21, Alexey Kardashevskiy [off-list ref] wrote:

quoted

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@redhat.com>
Suggested-by: Paul Mackerras <redacted>
Signed-off-by: Alexey Kardashevskiy <redacted>
---

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