Re: [PATCH] kvm: x86: remove vmx_vm_has_apicv() outside of hwapic_isr_update()

[Chen, Tiejun]

On 2014/12/1 19:43, Paolo Bonzini wrote:


On 01/12/2014 10:28, Tiejun Chen wrote:
In most cases calling hwapic_isr_update(), actually we always
check if kvm_apic_vid_enabled() == 1, and also actually,
kvm_apic_vid_enabled()
     -> kvm_x86_ops->vm_has_apicv()
         -> vmx_vm_has_apicv() or '0' in svm case

So its unnecessary to recall this inside hwapic_isr_update(), here
just remove vmx_vm_has_apicv() out and follow others.

If you want to do this, please NULL out the function pointer instead, as
KVM already does for hwapic_irr_update.

Are you saying something below?

if (enable_apicv)
        ...
else {
        kvm_x86_ops->hwapic_irr_update = NULL;

But there's a little bit difference to NULL out hwapic_isr_update(),

static int vmx_vm_has_apicv(struct kvm *kvm)
{
    return enable_apicv && irqchip_in_kernel(kvm);
}

Yes, I can do something like this,

static __init int hadware_setup(void)
{
        ...
        if (enable_apicv) {
                ...
                if (!irqchip_in_kernel(kvm))
                        kvm_x86_ops->hwapic_isr_update = NULL;       
        } else {
                ...
                kvm_x86_ops->hwapic_isr_update = NULL;

But this means we have to revise hadware_setup() to get 'kvm' inside, 
then rebase other callers to hwapic_isr_update(), is it really good?

Here what I will intend to do is trying to reduce some cost (reduplicate 
check) with a little code, so its may not be worth changing much more.

Tiejun


Paolo

Signed-off-by: Tiejun Chen <tiejun.c...@intel.com>
---
  arch/x86/kvm/lapic.c | 3 ++-
  arch/x86/kvm/vmx.c   | 3 ---
  2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e0e5642..2ddc426 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1739,7 +1739,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
        if (kvm_x86_ops->hwapic_irr_update)
                kvm_x86_ops->hwapic_irr_update(vcpu,
                                apic_find_highest_irr(apic));
-       kvm_x86_ops->hwapic_isr_update(vcpu->kvm, apic_find_highest_isr(apic));
+       if (kvm_apic_vid_enabled(vcpu->kvm))
+           kvm_x86_ops->hwapic_isr_update(vcpu->kvm, 
apic_find_highest_isr(apic));
        kvm_make_request(KVM_REQ_EVENT, vcpu);
        kvm_rtc_eoi_tracking_restore_one(vcpu);
  }
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6a951d8..f0c16a9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7406,9 +7406,6 @@ static void vmx_hwapic_isr_update(struct kvm *kvm, int 
isr)
        u16 status;
        u8 old;

-       if (!vmx_vm_has_apicv(kvm))
-               return;
-
        if (isr == -1)
                isr = 0;


--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html