linux-kernel - Re: [PATCH v2 08/12] x86/paravirt: remove no longer needed 32-bit pvops cruft

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Date:   Fri, 20 Nov 2020 13:08:05 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, luto@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Deep Shah <sdeep@...are.com>,
        "VMware, Inc." <pv-drivers@...are.com>
Subject: Re: [PATCH v2 08/12] x86/paravirt: remove no longer needed 32-bit
 pvops cruft

On Fri, Nov 20, 2020 at 12:46:26PM +0100, Juergen Gross wrote:
> +#define ____PVOP_CALL(rettype, op, clbr, call_clbr, extra_clbr, ...)	\
>  	({								\
>  		PVOP_CALL_ARGS;						\
>  		PVOP_TEST_NULL(op);					\
> +		BUILD_BUG_ON(sizeof(rettype) > sizeof(unsigned long));	\
> +		asm volatile(paravirt_alt(PARAVIRT_CALL)		\
> +			     : call_clbr, ASM_CALL_CONSTRAINT		\
> +			     : paravirt_type(op),			\
> +			       paravirt_clobber(clbr),			\
> +			       ##__VA_ARGS__				\
> +			     : "memory", "cc" extra_clbr);		\
> +		(rettype)(__eax & PVOP_RETMASK(rettype));		\
>  	})

This is now very similar to ____PVOP_VCALL() (note how PVOP_CALL_ARGS is
PVOP_VCALL_ARGS).

Could we get away with doing something horrible like:

#define ____PVOP_VCALL(X...) (void)____PVOP_CALL(long, X)

?