Re: [PATCH] Clear temporary interrupt blocking on halt in real mode

[Avi Kivity <avi@qumranet.com>]

Laurent Vivier wrote:
> When "halt" is emulated, skip_emulated_instruction() is called and interruptibility state is cleared.
> But when halt is emulated in real mode, skip_emulated_instruction() is not called and the interruptiblity state is not cleared.
>
> The following code, from gPXE, never exits from loop because interrupts are not delivered to increase %fs:(0x6c):
>
>         movl    %fs:(0x6c), %eax
> 1:      pushf
>         sti
>         hlt
>         popf
>         cmpl    %fs:(0x6c), %eax
>         je      1b
>
> This patch clears the interruptibility state when halt is emulated in real mode.
>
> Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
> ---
>  arch/x86/kvm/vmx.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index c4510fe..82c4324 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2329,7 +2329,17 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	    handle_rmode_exception(vcpu, intr_info & INTR_INFO_VECTOR_MASK,
>  								error_code)) {
>  		if (vcpu->arch.halt_request) {
> +			u32 interruptibility;
>  			vcpu->arch.halt_request = 0;
> +			/*
> +			 * We emulated an instruction, so temporary interrupt blocking
> +			 * should be removed, if set.
> +                         */
> +			interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
> +			if (interruptibility & 3)
> +				vmcs_write32(GUEST_INTERRUPTIBILITY_INFO,
> +					     interruptibility & ~3);
> +			vcpu->arch.interrupt_window_open = 1;
>  			return kvm_emulate_halt(vcpu);
>  		}
>  		return 1;
>   


Shouldn't interruptibility state be cleared if *any* instruction is 
emulated?

(of course, an emulated instruction may update interruptibility state 
itself, say sti).

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