Re: pre-preparation for in-kernel device model

Avi Kivity
2007-06-05T11:32:38Z

Dong, Eddie wrote:
> When in kernel device model is introduced, the guest interrupt status
> may get changed when after it injected an IRQ and thus guest see a
> messed interrupt state. This patch tries to disable irq at that window
> to avoid the confusion.
>
>
> Signed-off-by: Yaozu (Eddie) Dong <eddie.dong-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>
>
>
> diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
> index ef9e32b..0cf6ea7 100644
> --- a/drivers/kvm/vmx.c
> +++ b/drivers/kvm/vmx.c
> @@ -1977,9 +1977,6 @@ static int vmx_vcpu_run(struct kvm_vcpu *vcpu,
> struct kvm_run *kvm_run)
> int r;
>
> preempted:
> - if (!vcpu->mmio_read_completed)
> - do_interrupt_requests(vcpu, kvm_run);
> -
> if (vcpu->guest_debug.enabled)
> kvm_guest_debug_pre(vcpu);
>
> @@ -1996,9 +1993,16 @@ again:
> */
> vmcs_writel(HOST_CR0, read_cr0());
>
> + /*
> + * Disable interrupt to avoid future in kernel
> + * APIC interrupt state confuse.
> + */
> + asm ( "pushf; cli \n\t");
> + if (!vcpu->mmio_read_completed)
> + do_interrupt_requests(vcpu, kvm_run);
> +
>

This is broken. pushf changes %rsp, and if the compiler uses %rsp based
addressing (-fomit-frame-pointer), it will use the wrong addresses for
variables.

Suggest using local_irq_disable()/local_irq_enable() (and removing
pushf/popf from the entry/exit sequence).

--
error compiling committee.c: too many arguments to function