KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()

[PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()

Posted by Markus Elfring 3 months, 1 week ago

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Thu, 30 Oct 2025 21:43:20 +0100
Subject: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()

A pointer was assigned to a variable. The same pointer was used for
the destination parameter of a memcpy() call.
This function is documented in the way that the same value is returned.
Thus convert two separate statements into a direct variable assignment for
the return value from a memory copy action.

The source code was transformed by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 arch/powerpc/kvm/powerpc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 2ba057171ebe..ae28447b3e04 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -216,8 +216,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)

 			shared &= PAGE_MASK;
 			shared |= vcpu->arch.magic_page_pa & 0xf000;
-			new_shared = (void*)shared;
-			memcpy(new_shared, old_shared, 0x1000);
+			new_shared = memcpy(shared, old_shared, 0x1000);
 			vcpu->arch.shared = new_shared;
 		}
 #endif
-- 
2.51.1

Re: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()

Posted by Gautam Menghani 3 months, 1 week ago

On Thu, Oct 30, 2025 at 09:51:00PM +0100, Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Thu, 30 Oct 2025 21:43:20 +0100
> Subject: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()
> 
> A pointer was assigned to a variable. The same pointer was used for
> the destination parameter of a memcpy() call.
> This function is documented in the way that the same value is returned.
> Thus convert two separate statements into a direct variable assignment for
> the return value from a memory copy action.
> 
> The source code was transformed by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  arch/powerpc/kvm/powerpc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ba057171ebe..ae28447b3e04 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -216,8 +216,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
>  
>  			shared &= PAGE_MASK;
>  			shared |= vcpu->arch.magic_page_pa & 0xf000;
> -			new_shared = (void*)shared;
> -			memcpy(new_shared, old_shared, 0x1000);
> +			new_shared = memcpy(shared, old_shared, 0x1000);
>  			vcpu->arch.shared = new_shared;
>  		}
>  #endif

This patch does not compile

In file included from ./include/linux/string.h:382,
                 from ./arch/powerpc/include/asm/paca.h:16,
                 from ./arch/powerpc/include/asm/current.h:13,
                 from ./include/linux/sched.h:12,
                 from ./include/linux/resume_user_mode.h:6,
                 from ./include/linux/entry-virt.h:6,
                 from ./include/linux/kvm_host.h:5,
                 from arch/powerpc/kvm/powerpc.c:12:
arch/powerpc/kvm/powerpc.c: In function `kvmppc_kvm_pv´:
arch/powerpc/kvm/powerpc.c:219:45: error: passing argument 1 of `__builtin_dynamic_object_size´ makes pointer from integer without a cast [-Wint-conversion]
  219 |                         new_shared = memcpy(shared, old_shared, 0x1000);
      |                                             ^~~~~~
      |                                             |
      |                                             ulong {aka long unsigned int}


Thanks,
Gautam

Re: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()

Posted by Markus Elfring 3 months ago

>> A pointer was assigned to a variable. The same pointer was used for
>> the destination parameter of a memcpy() call.
>> This function is documented in the way that the same value is returned.
>> Thus convert two separate statements into a direct variable assignment for
>> the return value from a memory copy action.
…>> +++ b/arch/powerpc/kvm/powerpc.c
>> @@ -216,8 +216,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
>>  
>>  			shared &= PAGE_MASK;
>>  			shared |= vcpu->arch.magic_page_pa & 0xf000;
>> -			new_shared = (void*)shared;
>> -			memcpy(new_shared, old_shared, 0x1000);
>> +			new_shared = memcpy(shared, old_shared, 0x1000);
>>  			vcpu->arch.shared = new_shared;
>>  		}
>>  #endif
> 
> This patch does not compile
…> arch/powerpc/kvm/powerpc.c: In function `kvmppc_kvm_pv´:
> arch/powerpc/kvm/powerpc.c:219:45: error: passing argument 1 of `__builtin_dynamic_object_size´ makes pointer from integer without a cast [-Wint-conversion]
…

Will another subsequent patch variant become relevant for the proposed
source code transformation approach?

Regards,
Markus

Re: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()

Posted by David Laight 3 months, 1 week ago

On Thu, 30 Oct 2025 21:51:00 +0100
Markus Elfring <Markus.Elfring@web.de> wrote:

> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Thu, 30 Oct 2025 21:43:20 +0100
> Subject: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm_pv()
> 
> A pointer was assigned to a variable. The same pointer was used for
> the destination parameter of a memcpy() call.
> This function is documented in the way that the same value is returned.
> Thus convert two separate statements into a direct variable assignment for
> the return value from a memory copy action.
> 
> The source code was transformed by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  arch/powerpc/kvm/powerpc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ba057171ebe..ae28447b3e04 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -216,8 +216,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
>  
>  			shared &= PAGE_MASK;
>  			shared |= vcpu->arch.magic_page_pa & 0xf000;
> -			new_shared = (void*)shared;
> -			memcpy(new_shared, old_shared, 0x1000);
> +			new_shared = memcpy(shared, old_shared, 0x1000);

Did you even try to compile this??

>  			vcpu->arch.shared = new_shared;
>  		}
>  #endif