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KVM: x86: use kvfree_rcu to simplify the code

Message ID 20250122073456.2950-1-lirongqing@baidu.com (mailing list archive)
State New
Headers show
Series KVM: x86: use kvfree_rcu to simplify the code | expand

Commit Message

lirongqing Jan. 22, 2025, 7:34 a.m. UTC
From: Li RongQing <lirongqing@baidu.com>

The callback function of call_rcu() just calls kvfree(), so we can
use kvfree_rcu() instead of call_rcu() + callback function.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 arch/x86/kvm/lapic.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

Comments

Neeraj Upadhyay Jan. 23, 2025, 3:59 a.m. UTC | #1
On 1/22/2025 1:04 PM, lirongqing wrote:
> From: Li RongQing <lirongqing@baidu.com>
> 
> The callback function of call_rcu() just calls kvfree(), so we can
> use kvfree_rcu() instead of call_rcu() + callback function.
> 

Reword to imperative style?

The callback function of call_rcu() just calls kvfree(). So, use
kvfree_rcu() instead of call_rcu() + callback function.

> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
>  arch/x86/kvm/lapic.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 3c83951..d6e62a2 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -221,13 +221,6 @@ static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
>  	}
>  }
>  
> -static void kvm_apic_map_free(struct rcu_head *rcu)
> -{
> -	struct kvm_apic_map *map = container_of(rcu, struct kvm_apic_map, rcu);
> -
> -	kvfree(map);
> -}
> -
>  static int kvm_recalculate_phys_map(struct kvm_apic_map *new,
>  				    struct kvm_vcpu *vcpu,
>  				    bool *xapic_id_mismatch)
> @@ -489,7 +482,7 @@ static void kvm_recalculate_apic_map(struct kvm *kvm)
>  	mutex_unlock(&kvm->arch.apic_map_lock);
>  
>  	if (old)
> -		call_rcu(&old->rcu, kvm_apic_map_free);
> +		kvfree_rcu(old, rcu);
>  

Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>

Just a note: rcu_barrier() does not wait for kvfree_rcu() callbacks to complete. It only
waits for call_rcu() callbacks. For kvfree_rcu() callbacks, kvfree_rcu_barrier()
is required to wait for previously enqueued kvfree_rcu() callbacks to complete. As
rcu_barrier() is not used for apic_map free callbacks, this looks fine.


- Neeraj

>  	kvm_make_scan_ioapic_request(kvm);
>  }
Sean Christopherson Feb. 15, 2025, 12:50 a.m. UTC | #2
On Wed, 22 Jan 2025 15:34:56 +0800, lirongqing wrote:
> The callback function of call_rcu() just calls kvfree(), so we can
> use kvfree_rcu() instead of call_rcu() + callback function.

Applied to kvm-x86 misc, with a heavily rewritten changelog to call out the
rcu_barrier() wrinkles (I'm pretty sure it's, very technically, a bug fix).

Thanks!

[1/1] KVM: x86: use kvfree_rcu to simplify the code
      https://github.com/kvm-x86/linux/commit/82c470121c7b

--
https://github.com/kvm-x86/linux/tree/next
diff mbox series

Patch

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3c83951..d6e62a2 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -221,13 +221,6 @@  static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
 	}
 }
 
-static void kvm_apic_map_free(struct rcu_head *rcu)
-{
-	struct kvm_apic_map *map = container_of(rcu, struct kvm_apic_map, rcu);
-
-	kvfree(map);
-}
-
 static int kvm_recalculate_phys_map(struct kvm_apic_map *new,
 				    struct kvm_vcpu *vcpu,
 				    bool *xapic_id_mismatch)
@@ -489,7 +482,7 @@  static void kvm_recalculate_apic_map(struct kvm *kvm)
 	mutex_unlock(&kvm->arch.apic_map_lock);
 
 	if (old)
-		call_rcu(&old->rcu, kvm_apic_map_free);
+		kvfree_rcu(old, rcu);
 
 	kvm_make_scan_ioapic_request(kvm);
 }