linux-kernel - Re: [PATCH] KVM: PPC: Use pointer from memcpy() call for assignment in kvmppc_kvm

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Message-ID: <7d3339b1-9088-4e46-b6c5-7d2ff075aa3c@web.de>
Date: Mon, 3 Nov 2025 08:11:33 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: Gautam Menghani <gautam@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
 kvm@...r.kernel.org
Cc: Alexander Graf <agraf@...e.de>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 LKML <linux-kernel@...r.kernel.org>, kernel-janitors@...r.kernel.org,
 Miaoqian Lin <linmq006@...il.com>
Subject: Re: [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.
…>> +++ 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