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

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));
 
  out:
 	vcpu->arch.state = KVMPPC_VCPU_NOTREADY;

-- 
1.8.4.rc4

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

b/arch/powerpc/kvm/book3s_hv.c

*run, struct kvm_vcpu *vcpu)

				vcpu->arch.fault_dar, =

vcpu->arch.fault_dsisr);

			srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
		}
-	} while (r =3D=3D RESUME_GUEST);
+	} while ((r =3D=3D RESUME_GUEST_NV) || (r =3D=3D RESUME_GUEST));

How about

  while(!(r & RESUME_FLAG_HOST));

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).


Alex

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

On 04.02.2014, at 09:03, Alexey Kardashevskiy [off-list ref] wrote:

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

quoted

=20
On 10.01.2014, at 08:21, Alexey Kardashevskiy [off-list ref] wrote:
=20

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()

quoted

quoted

converts EMULATE_DONE to RESUME_GUEST_NV and this broke from the =

loop.

quoted

quoted

=20
This adds handling of RESUME_GUEST_NV in kvmppc_vcpu_run_hv().
=20
Cc: Michael S. Tsirkin <mst@redhat.com>
Suggested-by: Paul Mackerras <redacted>
Signed-off-by: Alexey Kardashevskiy <redacted>
---
=20
This definitely needs a better commit message. Please, help.
ps. it seems like ioeventfd never worked on ppc64. hm.
=20
---
arch/powerpc/kvm/book3s_hv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
=20

diff --git a/arch/powerpc/kvm/book3s_hv.c =

b/arch/powerpc/kvm/book3s_hv.c

quoted

quoted

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)

quoted

quoted

				vcpu->arch.fault_dar, =

vcpu->arch.fault_dsisr);

quoted

quoted

			srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
		}
-	} while (r =3D=3D RESUME_GUEST);
+	} while ((r =3D=3D RESUME_GUEST_NV) || (r =3D=3D RESUME_GUEST));

=20
How about
=20
 while(!(r & RESUME_FLAG_HOST));

=20
=20
Rather "while(!(r & RESUME_FLAG_HOST) && (r > 0));" and still not =

obvious

that this is really better.
=20
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 :)
=20
=20

quoted

That should cover all RESUME_GUEST_XXX cases just fine. Apart from =

that

quoted

I agree that we should check for ! FLAG_HOST bit rather than the =

actual

quoted

RESUME_GUEST value in all case where we check for it (read: please
update all places).

=20
There are 3 places remotely similar to this and none of them requires =

a fix

like above.

Not today. Then someone goes in and realizes that CEDE advanced version =
8 should clear r15 at which point you have to set RESUME_GUEST_NV and =
are in the same mess again. Let's just always treat RESUME_GUEST_NV and =
RESUME_GUEST as identical when checking for it.

If you like, add a small helper like

static inline bool is_resume_guest(int r) {
  return (r =3D=3D RESUME_GUEST || r =3D=3D RESUME_GUEST_NV);
}

in a header and use that one instead. That way we're guaranteed to be =
consistent.


Alex