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

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Message-ID: <5c123e7f-299d-2a4c-3e30-878537d71546@suse.com>
Date:   Fri, 20 Nov 2020 13:16:19 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 20.11.20 13:08, Peter Zijlstra wrote:
> 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)
> 
> ?

Oh, indeed. And in patch 9 the same could be done for the ALT variants.


Juergen

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