On Sun, Mar 24, 2013 at 07:44:47PM +0100, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
>
> If we are in guest mode, L0 can only inject events into L2 if L1 has
> nothing pending. Otherwise, L0 would overwrite L1's events and they
> would get lost. But even if no injection of L1 is pending, we do not
> want L0 to interrupt unnecessarily an on going vmentry with all its side
> effects on the vmcs. Therefore, injection shall be disallowed during
> L1->L2 transitions. This check is conceptually independent of
> nested_exit_on_intr.
>
> If L1 traps external interrupts, then we also need to look at L1's
> idt_vectoring_info_field. If it is empty, we can kick the guest from L2
> to L1, just like the previous code worked.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 28 ++++++++++++++++++++--------
> 1 files changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index d1bc834..30aa198 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4325,16 +4325,28 @@ static int vmx_nmi_allowed(struct kvm_vcpu *vcpu)
>
> static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
> {
> - if (is_guest_mode(vcpu) && nested_exit_on_intr(vcpu)) {
> + if (is_guest_mode(vcpu)) {
> struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> - if (to_vmx(vcpu)->nested.nested_run_pending ||
> - (vmcs12->idt_vectoring_info_field &
> - VECTORING_INFO_VALID_MASK))
> +
> + if (to_vmx(vcpu)->nested.nested_run_pending)
> return 0;
> - nested_vmx_vmexit(vcpu);
> - vmcs12->vm_exit_reason = EXIT_REASON_EXTERNAL_INTERRUPT;
> - vmcs12->vm_exit_intr_info = 0;
> - /* fall through to normal code, but now in L1, not L2 */
> + if (nested_exit_on_intr(vcpu)) {
> + /*
> + * Check if the idt_vectoring_info_field is free. We
> + * cannot raise EXIT_REASON_EXTERNAL_INTERRUPT if it
> + * isn't.
> + */
> + if (vmcs12->idt_vectoring_info_field &
> + VECTORING_INFO_VALID_MASK)
> + return 0;
After patch 2 I do not see how this can be true. Now this case is
handled by the common code: since event queue is not empty the code will not
get here.
> + nested_vmx_vmexit(vcpu);
> + vmcs12->vm_exit_reason =
> + EXIT_REASON_EXTERNAL_INTERRUPT;
> + vmcs12->vm_exit_intr_info = 0;
> + /*
> + * fall through to normal code, but now in L1, not L2
> + */
> + }
> }
>
> return (vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) &&
> --
> 1.7.3.4
--
Gleb.
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