[PATCH v3 01/10] KVM: add kvm_request_pending

From: Andrew Jones <drjones@redhat.com>
To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: marc.zyngier@arm.com, cdall@linaro.org, pbonzini@redhat.com
Subject: [PATCH v3 01/10] KVM: add kvm_request_pending
Date: Wed,  3 May 2017 18:06:26 +0200	[thread overview]
Message-ID: <20170503160635.21669-2-drjones@redhat.com> (raw)
In-Reply-To: <20170503160635.21669-1-drjones@redhat.com>

From: Radim Krčmář <rkrcmar@redhat.com>

A first step in vcpu->requests encapsulation.  Additionally, we now
use READ_ONCE() when accessing vcpu->requests, which ensures we
always load vcpu->requests when it's accessed.  This is important as
other threads can change it any time.  Also, READ_ONCE() documents
that vcpu->requests is used with other threads, likely requiring
memory barriers, which it does.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[ Documented the new use of READ_ONCE(). ]
Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 arch/mips/kvm/trap_emul.c  | 2 +-
 arch/powerpc/kvm/booke.c   | 2 +-
 arch/powerpc/kvm/powerpc.c | 5 ++---
 arch/s390/kvm/kvm-s390.c   | 2 +-
 arch/x86/kvm/x86.c         | 4 ++--
 include/linux/kvm_host.h   | 5 +++++
 6 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index b1fa53b252ea..9ac8b1d62643 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -1029,7 +1029,7 @@ static void kvm_trap_emul_check_requests(struct kvm_vcpu *vcpu, int cpu,
 	struct mm_struct *mm;
 	int i;
 
-	if (likely(!vcpu->requests))
+	if (likely(!kvm_request_pending(vcpu)))
 		return;
 
 	if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu)) {
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index ab968f60d14c..c427202b3cbb 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -682,7 +682,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
 
 	kvmppc_core_check_exceptions(vcpu);
 
-	if (vcpu->requests) {
+	if (kvm_request_pending(vcpu)) {
 		/* Exception delivery raised request; start over */
 		return 1;
 	}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 378ed9cee1f9..0ce1a219984e 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -52,8 +52,7 @@ EXPORT_SYMBOL_GPL(kvmppc_pr_ops);
 
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 {
-	return !!(v->arch.pending_exceptions) ||
-	       v->requests;
+	return !!(v->arch.pending_exceptions) || kvm_request_pending(v);
 }
 
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
@@ -105,7 +104,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
 		 */
 		smp_mb();
 
-		if (vcpu->requests) {
+		if (kvm_request_pending(vcpu)) {
 			/* Make sure we process requests preemptable */
 			local_irq_enable();
 			trace_kvm_check_requests(vcpu);
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 9ab89f73612a..66c33eb53707 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2396,7 +2396,7 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
 {
 retry:
 	kvm_s390_vcpu_request_handled(vcpu);
-	if (!vcpu->requests)
+	if (!kvm_request_pending(vcpu))
 		return 0;
 	/*
 	 * We use MMU_RELOAD just to re-arm the ipte notifier for the
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 073175e14083..92e643af848e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6720,7 +6720,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 	bool req_immediate_exit = false;
 
-	if (vcpu->requests) {
+	if (kvm_request_pending(vcpu)) {
 		if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
 			kvm_mmu_unload(vcpu);
 		if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))
@@ -6884,7 +6884,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			kvm_x86_ops->sync_pir_to_irr(vcpu);
 	}
 
-	if (vcpu->mode == EXITING_GUEST_MODE || vcpu->requests
+	if (vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu)
 	    || need_resched() || signal_pending(current)) {
 		vcpu->mode = OUTSIDE_GUEST_MODE;
 		smp_wmb();
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 94b12154e67c..b1f7d40a4ca4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1111,6 +1111,11 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
 	set_bit(req & KVM_REQUEST_MASK, &vcpu->requests);
 }
 
+static inline bool kvm_request_pending(struct kvm_vcpu *vcpu)
+{
+	return READ_ONCE(vcpu->requests);
+}
+
 static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu)
 {
 	return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests);
-- 
2.9.3

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
