* [PATCH] KVM: x86: init x2apic_enabled() once
@ 2019-07-23 13:06 luferry
2019-07-23 21:28 ` Krish Sadhukhan
2019-07-24 16:48 ` Sean Christopherson
0 siblings, 2 replies; 3+ messages in thread
From: luferry @ 2019-07-23 13:06 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, Borislav Petkov
Cc: H. Peter Anvin, x86, kvm, linux-kernel, luferry
From: luferry <luferry@163.com>
x2apic_eanbled() costs about 200 cycles
when guest trigger halt pretty high, pi ops in hotpath
Signed-off-by: luferry <luferry@163.com>
---
arch/x86/kvm/vmx/vmx.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d98eac371c0a..e17dbf011e47 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -186,6 +186,8 @@ static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush);
static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond);
static DEFINE_MUTEX(vmx_l1d_flush_mutex);
+static int __read_mostly host_x2apic_enabled;
+
/* Storage for pre module init parameter parsing */
static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush_param = VMENTER_L1D_FLUSH_AUTO;
@@ -1204,7 +1206,7 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
dest = cpu_physical_id(cpu);
- if (x2apic_enabled())
+ if (host_x2apic_enabled)
new.ndst = dest;
else
new.ndst = (dest << 8) & 0xFF00;
@@ -7151,7 +7153,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
dest = cpu_physical_id(vcpu->cpu);
- if (x2apic_enabled())
+ if (host_x2apic_enabled)
new.ndst = dest;
else
new.ndst = (dest << 8) & 0xFF00;
@@ -7221,7 +7223,7 @@ static int pi_pre_block(struct kvm_vcpu *vcpu)
*/
dest = cpu_physical_id(vcpu->pre_pcpu);
- if (x2apic_enabled())
+ if (host_x2apic_enabled)
new.ndst = dest;
else
new.ndst = (dest << 8) & 0xFF00;
@@ -7804,6 +7806,8 @@ static int __init vmx_init(void)
}
#endif
+ host_x2apic_enabled = x2apic_enabled();
+
r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
__alignof__(struct vcpu_vmx), THIS_MODULE);
if (r)
--
2.14.1.40.g8e62ba1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: init x2apic_enabled() once
2019-07-23 13:06 [PATCH] KVM: x86: init x2apic_enabled() once luferry
@ 2019-07-23 21:28 ` Krish Sadhukhan
2019-07-24 16:48 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Krish Sadhukhan @ 2019-07-23 21:28 UTC (permalink / raw)
To: luferry, Thomas Gleixner, Ingo Molnar, Borislav Petkov
Cc: H. Peter Anvin, x86, kvm, linux-kernel
On 07/23/2019 06:06 AM, luferry@163.com wrote:
> From: luferry <luferry@163.com>
>
> x2apic_eanbled() costs about 200 cycles
> when guest trigger halt pretty high, pi ops in hotpath
>
> Signed-off-by: luferry <luferry@163.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d98eac371c0a..e17dbf011e47 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -186,6 +186,8 @@ static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush);
> static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond);
> static DEFINE_MUTEX(vmx_l1d_flush_mutex);
>
> +static int __read_mostly host_x2apic_enabled;
> +
> /* Storage for pre module init parameter parsing */
> static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush_param = VMENTER_L1D_FLUSH_AUTO;
>
> @@ -1204,7 +1206,7 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
>
> dest = cpu_physical_id(cpu);
>
> - if (x2apic_enabled())
> + if (host_x2apic_enabled)
> new.ndst = dest;
> else
> new.ndst = (dest << 8) & 0xFF00;
> @@ -7151,7 +7153,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
>
> dest = cpu_physical_id(vcpu->cpu);
>
> - if (x2apic_enabled())
> + if (host_x2apic_enabled)
> new.ndst = dest;
> else
> new.ndst = (dest << 8) & 0xFF00;
> @@ -7221,7 +7223,7 @@ static int pi_pre_block(struct kvm_vcpu *vcpu)
> */
> dest = cpu_physical_id(vcpu->pre_pcpu);
>
> - if (x2apic_enabled())
> + if (host_x2apic_enabled)
> new.ndst = dest;
> else
> new.ndst = (dest << 8) & 0xFF00;
> @@ -7804,6 +7806,8 @@ static int __init vmx_init(void)
> }
> #endif
>
> + host_x2apic_enabled = x2apic_enabled();
> +
> r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
> __alignof__(struct vcpu_vmx), THIS_MODULE);
> if (r)
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: init x2apic_enabled() once
2019-07-23 13:06 [PATCH] KVM: x86: init x2apic_enabled() once luferry
2019-07-23 21:28 ` Krish Sadhukhan
@ 2019-07-24 16:48 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2019-07-24 16:48 UTC (permalink / raw)
To: luferry
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, H. Peter Anvin,
x86, kvm, linux-kernel
On Tue, Jul 23, 2019 at 09:06:08PM +0800, luferry@163.com wrote:
> From: luferry <luferry@163.com>
>
> x2apic_eanbled() costs about 200 cycles
> when guest trigger halt pretty high, pi ops in hotpath
>
> Signed-off-by: luferry <luferry@163.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d98eac371c0a..e17dbf011e47 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -186,6 +186,8 @@ static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush);
> static DEFINE_STATIC_KEY_FALSE(vmx_l1d_flush_cond);
> static DEFINE_MUTEX(vmx_l1d_flush_mutex);
>
> +static int __read_mostly host_x2apic_enabled;
> +
> /* Storage for pre module init parameter parsing */
> static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush_param = VMENTER_L1D_FLUSH_AUTO;
>
> @@ -1204,7 +1206,7 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
>
> dest = cpu_physical_id(cpu);
>
> - if (x2apic_enabled())
> + if (host_x2apic_enabled)
Instead of caching x2apic_enabled(), this can be:
if (x2apic_supported() && x2apic_mode)
which will get compiled out if CONFIG_X86_X2APIC=n.
It's quite suprising (to me) that 2apic_enabled() reads the MSR in the
first place, but at a glance the other users of x2apic_enabled() do need
to query the MSR and/or may be called before x2apic_mode is set.
> new.ndst = dest;
> else
> new.ndst = (dest << 8) & 0xFF00;
> @@ -7151,7 +7153,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
>
> dest = cpu_physical_id(vcpu->cpu);
>
> - if (x2apic_enabled())
> + if (host_x2apic_enabled)
> new.ndst = dest;
> else
> new.ndst = (dest << 8) & 0xFF00;
> @@ -7221,7 +7223,7 @@ static int pi_pre_block(struct kvm_vcpu *vcpu)
> */
> dest = cpu_physical_id(vcpu->pre_pcpu);
>
> - if (x2apic_enabled())
> + if (host_x2apic_enabled)
> new.ndst = dest;
> else
> new.ndst = (dest << 8) & 0xFF00;
> @@ -7804,6 +7806,8 @@ static int __init vmx_init(void)
> }
> #endif
>
> + host_x2apic_enabled = x2apic_enabled();
> +
> r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
> __alignof__(struct vcpu_vmx), THIS_MODULE);
> if (r)
> --
> 2.14.1.40.g8e62ba1
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-07-24 16:48 UTC | newest]
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2019-07-23 13:06 [PATCH] KVM: x86: init x2apic_enabled() once luferry
2019-07-23 21:28 ` Krish Sadhukhan
2019-07-24 16:48 ` Sean Christopherson
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