On Tue, Jul 20, 2010 at 04:17:07PM +0300, Avi Kivity wrote:
> Change the interrupt injection code to work from preemptible, interrupts
> enabled context.  This works by adding a ->cancel_injection() operation
> that undoes an injection in case we were not able to actually enter the guest
> (this condition could never happen with atomic injection).
> 
> Signed-off-by: Avi Kivity <a...@redhat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |    1 +
>  arch/x86/kvm/svm.c              |   12 ++++++++++++
>  arch/x86/kvm/vmx.c              |   11 +++++++++++
>  arch/x86/kvm/x86.c              |   27 ++++++++++++++-------------
>  4 files changed, 38 insertions(+), 13 deletions(-)
> 

> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4709,6 +4709,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>       if (unlikely(r))
>               goto out;
>  
> +     inject_pending_event(vcpu);
> +
> +     /* enable NMI/IRQ window open exits if needed */
> +     if (vcpu->arch.nmi_pending)
> +             kvm_x86_ops->enable_nmi_window(vcpu);
> +     else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
> +             kvm_x86_ops->enable_irq_window(vcpu);
> +
> +     if (kvm_lapic_enabled(vcpu)) {
> +             update_cr8_intercept(vcpu);
> +             kvm_lapic_sync_to_vapic(vcpu);
> +     }
> +
>       preempt_disable();
>  
>       kvm_x86_ops->prepare_guest_switch(vcpu);
> @@ -4727,23 +4740,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>               smp_wmb();
>               local_irq_enable();
>               preempt_enable();
> +             kvm_x86_ops->cancel_injection(vcpu);
>               r = 1;
>               goto out;
>       }
>  
> -     inject_pending_event(vcpu);
> -
> -     /* enable NMI/IRQ window open exits if needed */
> -     if (vcpu->arch.nmi_pending)
> -             kvm_x86_ops->enable_nmi_window(vcpu);
> -     else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
> -             kvm_x86_ops->enable_irq_window(vcpu);
> -
> -     if (kvm_lapic_enabled(vcpu)) {
> -             update_cr8_intercept(vcpu);
> -             kvm_lapic_sync_to_vapic(vcpu);
> -     }
> -
>       srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
>  
>       kvm_guest_enter();

This breaks

int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
{
        struct kvm_lapic *apic = vcpu->arch.apic;
        int highest_irr;

        /* This may race with setting of irr in __apic_accept_irq() and
         * value returned may be wrong, but kvm_vcpu_kick() in
         * __apic_accept_irq
         * will cause vmexit immediately and the value will be
         * recalculated
         * on the next vmentry.
         */

(also valid for nmi_pending and PIC). Can't simply move
atomic_set(guest_mode, 1) in preemptible section as that would make it
possible for kvm_vcpu_kick to IPI stale vcpu->cpu.

Also should undo vmx.rmode.* ?


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