Re: pre-preparation for in-kernel device model

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

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


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