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SubjectRe: [RFC PATCH 1/2] KVM: x86: always use "acknowledge interrupt on exit"
Date
Paolo Bonzini <pbonzini@redhat.com> writes:

> This is necessary to simplify handle_external_intr in the next patch.
> It means that nested KVM will require 3.16 on the host (or 3.17 if you
> have APICv enabled).
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/vmx.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index e185649fb8b7..4e9657730bf6 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3362,12 +3362,12 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
> vmx_capability.ept, vmx_capability.vpid);
> }
>
> - min = VM_EXIT_SAVE_DEBUG_CONTROLS;
> + min = VM_EXIT_SAVE_DEBUG_CONTROLS | VM_EXIT_ACK_INTR_ON_EXIT;
> #ifdef CONFIG_X86_64
> min |= VM_EXIT_HOST_ADDR_SPACE_SIZE;
> #endif
> opt = VM_EXIT_SAVE_IA32_PAT | VM_EXIT_LOAD_IA32_PAT |
> - VM_EXIT_ACK_INTR_ON_EXIT | VM_EXIT_CLEAR_BNDCFGS;
> + VM_EXIT_CLEAR_BNDCFGS;
> if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_EXIT_CTLS,
> &_vmexit_control) < 0)
> return -EIO;

Even if it breaks, this will complain quite loudly for the user to
upgrade. Maybe, a ack_intr specific message would be more direct (since that
is the one we are breaking) but imo it's fine either way.

Bandan


> @@ -3380,8 +3380,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
> return -EIO;
>
> if (!(_cpu_based_2nd_exec_control &
> - SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY) ||
> - !(_vmexit_control & VM_EXIT_ACK_INTR_ON_EXIT))
> + SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY))
> _pin_based_exec_control &= ~PIN_BASED_POSTED_INTR;
>
> min = VM_ENTRY_LOAD_DEBUG_CONTROLS;

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