linux-kernel - Re: [PATCH 2/4] x86/vmware: Add a header file for hypercall definitions

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Date:   Tue, 20 Aug 2019 21:23:01 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, pv-drivers@...are.com,
        Thomas Hellstrom <thellstrom@...are.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Doug Covelli <dcovelli@...are.com>
Subject: Re: [PATCH 2/4] x86/vmware: Add a header file for hypercall
 definitions

On Tue, 20 Aug 2019, Thomas Hellström (VMware) wrote:
> On 8/20/19 3:42 PM, Thomas Gleixner wrote:
> > > What confuses me a bit is, if it's clarity we're after, why don't people
> > > use
> > > 
> > > #define VMWARE_HYPERCALL 					\
> > > 	ALTERNATIVE_2("inl (%%dx)", 				\
> > > 		      "vmcall", X86_FEATURE_VMW_VMCALL,		\	
> > > 		      "vmmcall", X86_FEATURE_VMW_VMMCALL)
> > > 
> > > Seems to build fine here. Is it fear of old assemblers not supporting, for
> > > example vmmcall
> > The requirement for binutils is version >= 2.21. If 2.21 supports vmcall and
> > vmmcall all good.
> > 
> > Thanks,
> > 
> > 	tglx
> 
> So I tested 2.20.1 and 2.21.1 from ftp.gnu.org/gnu/binutils, and both seem to
> assemble (as-new) and disassemble (objdump -S) vmcall and vmmcall fine so I
> think we should be OK using the mnemonic format then.

Perfect!