KVM: PPC: Book3S HV: Remove vcpu->arch.dec usage

Message ID 20171219145624.46724-1-agraf@suse.de
State New
Headers show
Series
  • KVM: PPC: Book3S HV: Remove vcpu->arch.dec usage
Related show

Commit Message

Alexander Graf Dec. 19, 2017, 2:56 p.m.
On Book3S in HV mode, we don't use the vcpu->arch.dec field at all.
Instead, all logic is built around vcpu->arch.dec_expires.

So let's remove the one remaining piece of code that was setting it.

Signed-off-by: Alexander Graf <agraf@suse.de>

---

Looking through the DEC logic, I fail to see any code that allows
save or restore of DEC. Do we maybe miss out on that register for
(live) migration?
---
 arch/powerpc/kvm/book3s_hv_rmhandlers.S | 1 -
 1 file changed, 1 deletion(-)

Comments

Paul Mackerras Jan. 11, 2018, 10:01 a.m. | #1
On Tue, Dec 19, 2017 at 03:56:24PM +0100, Alexander Graf wrote:
> On Book3S in HV mode, we don't use the vcpu->arch.dec field at all.
> Instead, all logic is built around vcpu->arch.dec_expires.
> 
> So let's remove the one remaining piece of code that was setting it.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>

Thanks, applied to my kvm-ppc-next branch.

> Looking through the DEC logic, I fail to see any code that allows
> save or restore of DEC. Do we maybe miss out on that register for
> (live) migration?

Yes, it looks like we do.  I'm amazed no-one has noticed before.  I'll
fix it.

Paul.
--
To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 2659844784b8..c8ffd69adfec 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -957,7 +957,6 @@  ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
 	mftb	r7
 	subf	r3,r7,r8
 	mtspr	SPRN_DEC,r3
-	std	r3,VCPU_DEC(r4)
 
 	ld	r5, VCPU_SPRG0(r4)
 	ld	r6, VCPU_SPRG1(r4)