* [PATCH] KVM: avoid unnecessary bitmap clear ops
@ 2019-10-25 2:24 Miaohe Lin
2019-10-25 9:42 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Miaohe Lin @ 2019-10-25 2:24 UTC (permalink / raw)
To: pbonzini, rkrcmar, sean.j.christopherson, vkuznets, wanpengli,
jmattson, joro, tglx, mingo, bp, hpa
Cc: x86, kvm, linux-kernel, linmiaohe
When set one bit in bitmap, there is no need to
clear it before.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
arch/x86/kvm/svm.c | 3 ++-
arch/x86/kvm/x86.c | 3 ++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ca200b50cde4..d997d011a942 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2044,9 +2044,10 @@ static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
- entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
if (svm->avic_is_running)
entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
+ else
+ entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
avic_update_iommu_vcpu_affinity(vcpu, h_physical_id,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ff395f812719..9b535888ea90 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1036,9 +1036,10 @@ static void kvm_update_dr7(struct kvm_vcpu *vcpu)
else
dr7 = vcpu->arch.dr7;
kvm_x86_ops->set_dr7(vcpu, dr7);
- vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_BP_ENABLED;
if (dr7 & DR7_BP_EN_MASK)
vcpu->arch.switch_db_regs |= KVM_DEBUGREG_BP_ENABLED;
+ else
+ vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_BP_ENABLED;
}
static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)
--
2.19.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: avoid unnecessary bitmap clear ops
2019-10-25 2:24 [PATCH] KVM: avoid unnecessary bitmap clear ops Miaohe Lin
@ 2019-10-25 9:42 ` Paolo Bonzini
0 siblings, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2019-10-25 9:42 UTC (permalink / raw)
To: Miaohe Lin, rkrcmar, sean.j.christopherson, vkuznets, wanpengli,
jmattson, joro, tglx, mingo, bp, hpa
Cc: x86, kvm, linux-kernel
On 25/10/19 04:24, Miaohe Lin wrote:
> When set one bit in bitmap, there is no need to
> clear it before.
Hi,
in general the Linux coding style prefers:
a = x;
if (...);
a = y;
to
if (...)
a = y;
else
a = x;
which is why these lines were written this way.
Thanks,
Paolo
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> arch/x86/kvm/svm.c | 3 ++-
> arch/x86/kvm/x86.c | 3 ++-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index ca200b50cde4..d997d011a942 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2044,9 +2044,10 @@ static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
> entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
>
> - entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
> if (svm->avic_is_running)
> entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
> + else
> + entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
>
> WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
> avic_update_iommu_vcpu_affinity(vcpu, h_physical_id,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ff395f812719..9b535888ea90 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1036,9 +1036,10 @@ static void kvm_update_dr7(struct kvm_vcpu *vcpu)
> else
> dr7 = vcpu->arch.dr7;
> kvm_x86_ops->set_dr7(vcpu, dr7);
> - vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_BP_ENABLED;
> if (dr7 & DR7_BP_EN_MASK)
> vcpu->arch.switch_db_regs |= KVM_DEBUGREG_BP_ENABLED;
> + else
> + vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_BP_ENABLED;
> }
>
> static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: avoid unnecessary bitmap clear ops
@ 2019-10-25 9:49 linmiaohe
0 siblings, 0 replies; 3+ messages in thread
From: linmiaohe @ 2019-10-25 9:49 UTC (permalink / raw)
To: Paolo Bonzini
Cc: rkrcmar, sean.j.christopherson, vkuznets, wanpengli, jmattson,
joro, tglx, mingo, bp, hpa, x86, kvm, linux-kernel
On 25/10/19 17:43, Paolo wrote:
> On 25/10/19 04:24, Miaohe Lin wrote:
>> When set one bit in bitmap, there is no need to clear it before.
>
>Hi,
>
>in general the Linux coding style prefers:
>
> a = x;
> if (...);
> a = y;
>
>to
>
> if (...)
> a = y;
> else
> a = x;
>
>which is why these lines were written this way.
Many thanks for your explanation. I see.
Have a nice day.
>
>Thanks,
>
>Paolo
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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