Re: [PATCH] Using the tlb flush util function where applicable

["Radim Krčmář" <rkrcmar@redhat.com>]

2014-09-12 17:06-0400, Liang Chen:
> Using kvm_mmu_flush_tlb as the other places to make sure vcpu
>  stat is incremented
> 
> Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
> ---

Good catch.

>  arch/x86/kvm/vmx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index bfe11cf..439682e 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1810,7 +1810,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  		struct desc_ptr *gdt = &__get_cpu_var(host_gdt);
>  		unsigned long sysenter_esp;
>  
> -		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> +		kvm_mmu_flush_tlb(vcpu);
>  		local_irq_disable();
>  		crash_disable_local_vmclear(cpu);
>  

And to hijack this thread ...
I noticed three other deficits in stat.tlb_flush, patch below.

Do you prefer the current behavior?

--- 8< ---
KVM: x86: count actual tlb flushes

- we count KVM_REQ_TLB_FLUSH requests, not actual flushes
  (KVM can have multiple requests for one flush)
- flushes from kvm_flush_remote_tlbs aren't counted
- it's easy to make a direct request by mistake

Solve these by postponing the counting to kvm_check_request().

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
(And what about a possible followup patch that replaces
 kvm_mmu_flush_tlb() with kvm_make_request() again?
 It would free the namespace a bit and we could call something
 similarly named from vcpu_enter_guest() to do the job.)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9314678..b41fd97 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3452,7 +3452,6 @@ static void nonpaging_init_context(struct kvm_vcpu *vcpu,
 
 void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
 {
-	++vcpu->stat.tlb_flush;
 	kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_flush_tlb);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 916e895..0f0ad08 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6041,8 +6041,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		}
 		if (kvm_check_request(KVM_REQ_MMU_SYNC, vcpu))
 			kvm_mmu_sync_roots(vcpu);
-		if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu))
+		if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu)) {
+			++vcpu->stat.tlb_flush;
 			kvm_x86_ops->tlb_flush(vcpu);
+		}
 		if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {
 			vcpu->run->exit_reason = KVM_EXIT_TPR_ACCESS;
 			r = 0;