Re: [PATCH v4 02/11] KVM: add kvm_request_pending

Christoffer Dall
2017-06-01T10:35:04Z

On Tue, May 16, 2017 at 04:20:26AM +0200, Andrew Jones wrote:
> 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() 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>

> ---
> arch/mips/kvm/trap_emul.c | 2 +-
> arch/mips/kvm/vz.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 +++++
> 7 files changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
> index a563759fd142..6a0d7040d882 100644
> --- 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 71d8856ade64..74805035edc8 100644
> --- 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 3eaac3809977..071b87ee682f 100644
> --- 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 f7cf2cd564ef..fd64f087737c 100644
> --- 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 689ac48361c6..ad41e0fa3a21 100644
> --- 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 464da936c53d..f81060518635 100644
> --- 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 3724b51aab64..0b50e7b35ed4 100644
> --- 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);
> --
> 2.9.3
>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu