KVM: add kvm_request_pending

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() and converted another check
  in arch/mips/kvm/vz.c ]
Signed-off-by: Andrew Jones <drjones@redhat.com>
Acked-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index a563759..6a0d704 100644 (file)
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -1094,7 +1094,7 @@ 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/mips/kvm/vz.c b/arch/mips/kvm/vz.c
index 71d8856..7480503 100644 (file)
--- a/arch/mips/kvm/vz.c
+++ b/arch/mips/kvm/vz.c
@@ -2337,7 +2337,7 @@ static int kvm_vz_check_requests(struct kvm_vcpu *vcpu, int cpu)
        int ret = 0;
        int i;
 
-       if (!vcpu->requests)
+       if (!kvm_request_pending(vcpu))
                return 0;
 
        if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu)) {

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 3eaac38..071b87e 100644 (file)
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -687,7 +687,7 @@ 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 f7cf2cd..fd64f08 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -55,8 +55,7 @@ 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)
@@ -108,7 +107,7 @@ 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 689ac48..ad41e0f 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2440,7 +2440,7 @@ 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 464da93..f810605 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6710,7 +6710,7 @@ 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))
@@ -6874,7 +6874,7 @@ 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 3724b51..0b50e7b 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1105,6 +1105,11 @@ 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);