[PATCH 05/12] KVM: PPC: Fix updates of vcpu->cpu on HV KVM

From: Paul Mackerras <paulus@samba.org>
To: Alexander Graf <agraf@suse.de>
Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: [PATCH 05/12] KVM: PPC: Fix updates of vcpu->cpu on HV KVM
Date: Tue, 28 Aug 2012 22:34:52 +1000	[thread overview]
Message-ID: <20120828123452.GF7258@bloggs.ozlabs.ibm.com> (raw)
In-Reply-To: <20120828123043.GA7258@bloggs.ozlabs.ibm.com>

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

This patch removes the powerpc "generic" updates of vcpu->cpu in
load and put, and moves them to the various backends.

The reason is that "HV" KVM does its own sauce with that field
and the generic updates might corrupt it. The field contains the
CPU# of the -first- HW CPU of the core always for all the VCPU
threads of a core (the one that's online from a host Linux
perspective).

However, the preempt notifiers are going to be called on the
threads VCPUs when they are running (due to them sleeping on our
private waitqueue) causing unload to be called, potentially
clobbering the value.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 arch/powerpc/kvm/book3s_pr.c |    3 ++-
 arch/powerpc/kvm/booke.c     |    2 ++
 arch/powerpc/kvm/powerpc.c   |    2 --
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index fdadc9e..4490deb 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -64,7 +64,7 @@ void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	svcpu->slb_max = to_book3s(vcpu)->slb_shadow_max;
 	svcpu_put(svcpu);
 #endif
-
+	vcpu->cpu = smp_processor_id();
 #ifdef CONFIG_PPC_BOOK3S_32
 	current->thread.kvm_shadow_vcpu = to_book3s(vcpu)->shadow_vcpu;
 #endif
@@ -84,6 +84,7 @@ void kvmppc_core_vcpu_put(struct kvm_vcpu *vcpu)
 	kvmppc_giveup_ext(vcpu, MSR_FP);
 	kvmppc_giveup_ext(vcpu, MSR_VEC);
 	kvmppc_giveup_ext(vcpu, MSR_VSX);
+	vcpu->cpu = -1;
 }
 
 int kvmppc_core_check_requests(struct kvm_vcpu *vcpu)
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 5144057..ad73563 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -1504,12 +1504,14 @@ void kvmppc_decrementer_func(unsigned long data)
 
 void kvmppc_booke_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+	vcpu->cpu = smp_processor_id();
 	current->thread.kvm_vcpu = vcpu;
 }
 
 void kvmppc_booke_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	current->thread.kvm_vcpu = NULL;
+	vcpu->cpu = -1;
 }
 
 int __init kvmppc_booke_init(void)
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 72764ba..1241b29 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -502,7 +502,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	mtspr(SPRN_VRSAVE, vcpu->arch.vrsave);
 #endif
 	kvmppc_core_vcpu_load(vcpu, cpu);
-	vcpu->cpu = smp_processor_id();
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -511,7 +510,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 #ifdef CONFIG_BOOKE
 	vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
 #endif
-	vcpu->cpu = -1;
 }
 
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
-- 
1.7.10.rc3.219.g53414
