* [PATCH] KVM: x86: Optimize local variable in start_sw_tscdeadline()
@ 2024-08-14 20:33 Thorsten Blum
2024-08-14 21:33 ` Sean Christopherson
2024-08-23 23:47 ` Sean Christopherson
0 siblings, 2 replies; 3+ messages in thread
From: Thorsten Blum @ 2024-08-14 20:33 UTC (permalink / raw)
To: seanjc, pbonzini, tglx, mingo, bp, dave.hansen, x86, hpa
Cc: kvm, linux-kernel, Thorsten Blum
Change the data type of the local variable this_tsc_khz to u32 because
virtual_tsc_khz is also declared as u32.
Since do_div() casts the divisor to u32 anyway, changing the data type
of this_tsc_khz to u32 also removes the following Coccinelle/coccicheck
warning reported by do_div.cocci:
WARNING: do_div() does a 64-by-32 division, please consider using div64_ul instead
Compile-tested only.
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
---
arch/x86/kvm/lapic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index a7172ba59ad2..40ff955c1859 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1946,7 +1946,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
u64 ns = 0;
ktime_t expire;
struct kvm_vcpu *vcpu = apic->vcpu;
- unsigned long this_tsc_khz = vcpu->arch.virtual_tsc_khz;
+ u32 this_tsc_khz = vcpu->arch.virtual_tsc_khz;
unsigned long flags;
ktime_t now;
--
2.45.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: Optimize local variable in start_sw_tscdeadline()
2024-08-14 20:33 [PATCH] KVM: x86: Optimize local variable in start_sw_tscdeadline() Thorsten Blum
@ 2024-08-14 21:33 ` Sean Christopherson
2024-08-23 23:47 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2024-08-14 21:33 UTC (permalink / raw)
To: Thorsten Blum
Cc: pbonzini, tglx, mingo, bp, dave.hansen, x86, hpa, kvm,
linux-kernel
On Wed, Aug 14, 2024, Thorsten Blum wrote:
> Change the data type of the local variable this_tsc_khz to u32 because
> virtual_tsc_khz is also declared as u32.
Heh, thought this looked familiar[*]. I'll plan on applying this for 6.12.
[*] https://lore.kernel.org/all/ZT_WBanoip8zhxis@google.com
> Since do_div() casts the divisor to u32 anyway, changing the data type
> of this_tsc_khz to u32 also removes the following Coccinelle/coccicheck
> warning reported by do_div.cocci:
>
> WARNING: do_div() does a 64-by-32 division, please consider using div64_ul instead
>
> Compile-tested only.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
> ---
> arch/x86/kvm/lapic.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index a7172ba59ad2..40ff955c1859 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1946,7 +1946,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
> u64 ns = 0;
> ktime_t expire;
> struct kvm_vcpu *vcpu = apic->vcpu;
> - unsigned long this_tsc_khz = vcpu->arch.virtual_tsc_khz;
> + u32 this_tsc_khz = vcpu->arch.virtual_tsc_khz;
> unsigned long flags;
> ktime_t now;
>
> --
> 2.45.2
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: x86: Optimize local variable in start_sw_tscdeadline()
2024-08-14 20:33 [PATCH] KVM: x86: Optimize local variable in start_sw_tscdeadline() Thorsten Blum
2024-08-14 21:33 ` Sean Christopherson
@ 2024-08-23 23:47 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2024-08-23 23:47 UTC (permalink / raw)
To: Sean Christopherson, pbonzini, tglx, mingo, bp, dave.hansen, x86,
hpa, Thorsten Blum
Cc: kvm, linux-kernel
On Wed, 14 Aug 2024 22:33:46 +0200, Thorsten Blum wrote:
> Change the data type of the local variable this_tsc_khz to u32 because
> virtual_tsc_khz is also declared as u32.
>
> Since do_div() casts the divisor to u32 anyway, changing the data type
> of this_tsc_khz to u32 also removes the following Coccinelle/coccicheck
> warning reported by do_div.cocci:
>
> [...]
Applied to kvm-x86 misc, thanks!
[1/1] KVM: x86: Optimize local variable in start_sw_tscdeadline()
https://github.com/kvm-x86/linux/commit/1448d4a935ab
--
https://github.com/kvm-x86/linux/tree/next
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-08-14 21:33 ` Sean Christopherson
2024-08-23 23:47 ` Sean Christopherson
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