On 10.01.2014, at 02:18, Scott Wood <scottwood@xxxxxxxxxxxxx> wrote:
> Simplify the handling of lazy EE by going directly from fully-enabled
> to hard-disabled. This replaces the lazy_irq_pending() check
> (including its misplaced kvm_guest_exit() call).
>
> As suggested by Tiejun Chen, move the interrupt disabling into
> kvmppc_prepare_to_enter() rather than have each caller do it. Also
> move the IRQ enabling on heavyweight exit into
> kvmppc_prepare_to_enter().
>
> Signed-off-by: Scott Wood <scottwood@xxxxxxxxxxxxx>
Thanks, applied to kvm-ppc-queue.
Alex
> ---
> v2:
> - rebased
> - removed redundant (on 64-bit) and possibly performance-affecting WARNs
> - addressed cosmetic feedback
>
> arch/powerpc/include/asm/kvm_ppc.h | 6 ++++++
> arch/powerpc/kvm/book3s_pr.c | 14 ++++++--------
> arch/powerpc/kvm/booke.c | 12 +++++-------
> arch/powerpc/kvm/powerpc.c | 26 +++++++++-----------------
> 4 files changed, 26 insertions(+), 32 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index c8317fb..e64881cd 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -455,6 +455,12 @@ static inline void kvmppc_fix_ee_before_entry(void)
> trace_hardirqs_on();
>
> #ifdef CONFIG_PPC64
> + /*
> + * To avoid races, the caller must have gone directly from having
> + * interrupts fully-enabled to hard-disabled.
> + */
> + WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS);
> +
> /* Only need to enable IRQs by hard enabling them after this */
> local_paca->irq_happened = 0;
> local_paca->soft_enabled = 1;
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index fe14ca3..ce7accc 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -1023,14 +1023,14 @@ program_interrupt:
> * and if we really did time things so badly, then we just exit
> * again due to a host external interrupt.
> */
> - local_irq_disable();
> s = kvmppc_prepare_to_enter(vcpu);
> - if (s <= 0) {
> - local_irq_enable();
> + if (s <= 0)
> r = s;
> - } else {
> + else {
> + /* interrupts now hard-disabled */
> kvmppc_fix_ee_before_entry();
> }
> +
> kvmppc_handle_lost_ext(vcpu);
> }
>
> @@ -1277,12 +1277,10 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> * really did time things so badly, then we just exit again due to
> * a host external interrupt.
> */
> - local_irq_disable();
> ret = kvmppc_prepare_to_enter(vcpu);
> - if (ret <= 0) {
> - local_irq_enable();
> + if (ret <= 0)
> goto out;
> - }
> + /* interrupts now hard-disabled */
>
> /* Save FPU state in stack */
> if (current->thread.regs->msr & MSR_FP)
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 53e65a2..626b431 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -643,7 +643,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
> local_irq_enable();
> kvm_vcpu_block(vcpu);
> clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
> - local_irq_disable();
> + hard_irq_disable();
>
> kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
> r = 1;
> @@ -692,13 +692,12 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> return -EINVAL;
> }
>
> - local_irq_disable();
> s = kvmppc_prepare_to_enter(vcpu);
> if (s <= 0) {
> - local_irq_enable();
> ret = s;
> goto out;
> }
> + /* interrupts now hard-disabled */
>
> #ifdef CONFIG_PPC_FPU
> /* Save userspace FPU state in stack */
> @@ -1217,12 +1216,11 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> * aren't already exiting to userspace for some other reason.
> */
> if (!(r & RESUME_HOST)) {
> - local_irq_disable();
> s = kvmppc_prepare_to_enter(vcpu);
> - if (s <= 0) {
> - local_irq_enable();
> + if (s <= 0)
> r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
> - } else {
> + else {
> + /* interrupts now hard-disabled */
> kvmppc_fix_ee_before_entry();
> }
> }
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 9ae9768..ea65029 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -68,14 +68,16 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> */
> int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> {
> - int r = 1;
> + int r;
> +
> + WARN_ON(irqs_disabled());
> + hard_irq_disable();
>
> - WARN_ON_ONCE(!irqs_disabled());
> while (true) {
> if (need_resched()) {
> local_irq_enable();
> cond_resched();
> - local_irq_disable();
> + hard_irq_disable();
> continue;
> }
>
> @@ -101,7 +103,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> local_irq_enable();
> trace_kvm_check_requests(vcpu);
> r = kvmppc_core_check_requests(vcpu);
> - local_irq_disable();
> + hard_irq_disable();
> if (r > 0)
> continue;
> break;
> @@ -113,22 +115,12 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
> continue;
> }
>
> -#ifdef CONFIG_PPC64
> - /* lazy EE magic */
> - hard_irq_disable();
> - if (lazy_irq_pending()) {
> - /* Got an interrupt in between, try again */
> - local_irq_enable();
> - local_irq_disable();
> - kvm_guest_exit();
> - continue;
> - }
> -#endif
> -
> kvm_guest_enter();
> - break;
> + return 1;
> }
>
> + /* return to host */
> + local_irq_enable();
> return r;
> }
> EXPORT_SYMBOL_GPL(kvmppc_prepare_to_enter);
> --
> 1.8.3.2
>
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