* [PATCH] KVM: x86: MMU: Use clear_page() instead of init_shadow_page_table()
@ 2015-12-18 9:54 Takuya Yoshikawa
2015-12-18 18:08 ` Paolo Bonzini
0 siblings, 1 reply; 2+ messages in thread
From: Takuya Yoshikawa @ 2015-12-18 9:54 UTC (permalink / raw)
To: pbonzini; +Cc: kvm, linux-kernel
Not just in order to clean up the code, but to make it faster by using
enhanced instructions: the initialization became 20-30% faster on our
testing machine.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
---
arch/x86/kvm/mmu.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a1a3d19..7f5a82b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2041,14 +2041,6 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
}
}
-static void init_shadow_page_table(struct kvm_mmu_page *sp)
-{
- int i;
-
- for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
- sp->spt[i] = 0ull;
-}
-
static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
{
sp->write_flooding_count = 0;
@@ -2128,7 +2120,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
account_shadowed(vcpu->kvm, sp);
}
sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
- init_shadow_page_table(sp);
+ clear_page(sp->spt);
trace_kvm_mmu_get_page(sp, true);
return sp;
}
--
2.1.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM: x86: MMU: Use clear_page() instead of init_shadow_page_table()
2015-12-18 9:54 [PATCH] KVM: x86: MMU: Use clear_page() instead of init_shadow_page_table() Takuya Yoshikawa
@ 2015-12-18 18:08 ` Paolo Bonzini
0 siblings, 0 replies; 2+ messages in thread
From: Paolo Bonzini @ 2015-12-18 18:08 UTC (permalink / raw)
To: Takuya Yoshikawa; +Cc: kvm, linux-kernel
On 18/12/2015 10:54, Takuya Yoshikawa wrote:
> Not just in order to clean up the code, but to make it faster by using
> enhanced instructions: the initialization became 20-30% faster on our
> testing machine.
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Applied locally, but I'm not sure when it will appear on kernel.org...
it depends on the amount of testing I can do next week before the
holidays. Anyway, it's not lost. :)
Paolo
> ---
> arch/x86/kvm/mmu.c | 10 +---------
> 1 file changed, 1 insertion(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index a1a3d19..7f5a82b 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2041,14 +2041,6 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
> }
> }
>
> -static void init_shadow_page_table(struct kvm_mmu_page *sp)
> -{
> - int i;
> -
> - for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
> - sp->spt[i] = 0ull;
> -}
> -
> static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
> {
> sp->write_flooding_count = 0;
> @@ -2128,7 +2120,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> account_shadowed(vcpu->kvm, sp);
> }
> sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
> - init_shadow_page_table(sp);
> + clear_page(sp->spt);
> trace_kvm_mmu_get_page(sp, true);
> return sp;
> }
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2015-12-18 9:54 [PATCH] KVM: x86: MMU: Use clear_page() instead of init_shadow_page_table() Takuya Yoshikawa
2015-12-18 18:08 ` Paolo Bonzini
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