linux-kernel - Re: [PATCH] kvm: selftests: avoid type punning

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Date:   Mon, 20 May 2019 15:43:28 +0200
From:   Thomas Huth <thuth@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH] kvm: selftests: avoid type punning

On 20/05/2019 15.38, Paolo Bonzini wrote:
> Avoid warnings from -Wstrict-aliasing by using memcpy.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  tools/testing/selftests/kvm/lib/ucall.c                        | 2 +-
>  tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/ucall.c b/tools/testing/selftests/kvm/lib/ucall.c
> index a2ab38be2f47..b701a01cfcb6 100644
> --- a/tools/testing/selftests/kvm/lib/ucall.c
> +++ b/tools/testing/selftests/kvm/lib/ucall.c
> @@ -142,7 +142,7 @@ uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
>  		vm_vaddr_t gva;
>  		TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
>  			    "Unexpected ucall exit mmio address access");
> -		gva = *(vm_vaddr_t *)run->mmio.data;
> +		memcpy(&gva, run->mmio.data, sizeof(gva));
>  		memcpy(uc, addr_gva2hva(vm, gva), sizeof(*uc));
>  	}
>  
> diff --git a/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
> index 61a2163cf9f1..9d62e2c7e024 100644
> --- a/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
> @@ -75,7 +75,7 @@ void set_revision_id_for_vmcs12(struct kvm_nested_state *state,
>  				u32 vmcs12_revision)
>  {
>  	/* Set revision_id in vmcs12 to vmcs12_revision. */
> -	*(u32 *)(state->data) = vmcs12_revision;
> +	memcpy(state->data, &vmcs12_revision, sizeof(u32));
>  }
>  
>  void set_default_state(struct kvm_nested_state *state)
> 

Reviewed-by: Thomas Huth <thuth@...hat.com>