linux-kernel - Re: [PATCH] KVM: x86: remove ignored type attribute

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Date:   Tue, 27 Jun 2017 16:31:33 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Nick Desaulniers <nick.desaulniers@...il.com>
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: remove ignored type attribute



On 23/06/2017 06:41, Nick Desaulniers wrote:
> The macro insn_fetch marks the 'type' argument as having a specified
> alignment.  Type attributes can only be applied to structs, unions, or
> enums, but insn_fetch is only ever invoked with integral types, so Clang
> produces 19 -Wignored-attributes warnings for this source file.
> 
> Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
> ---
>  arch/x86/kvm/emulate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 7611c034bf95..409081977e59 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -900,7 +900,7 @@ static __always_inline int do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt,
>  	if (rc != X86EMUL_CONTINUE)					\
>  		goto done;						\
>  	ctxt->_eip += sizeof(_type);					\
> -	_x = *(_type __aligned(1) *) ctxt->fetch.ptr;			\
> +	_x = *(_type *) ctxt->fetch.ptr;			\
>  	ctxt->fetch.ptr += sizeof(_type);				\
>  	_x;								\
>  })
> 

Can you make a patch that uses memcpy instead?  Both GCC and clang will
compile it to a simple load.

Paolo