linux-kernel - Re: [PATCH v3 07/16] x86/kvm/emulate: Introduce EM_ASM

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Message-ID: <20250818103709.GE3289052@noisy.programming.kicks-ass.net>
Date: Mon, 18 Aug 2025 12:37:09 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: x86@...nel.org, kys@...rosoft.com, haiyangz@...rosoft.com,
	wei.liu@...nel.org, decui@...rosoft.com, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	hpa@...or.com, pbonzini@...hat.com, ardb@...nel.org,
	kees@...nel.org, Arnd Bergmann <arnd@...db.de>,
	gregkh@...uxfoundation.org, jpoimboe@...nel.org,
	linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, linux-efi@...r.kernel.org,
	samitolvanen@...gle.com, ojeda@...nel.org
Subject: Re: [PATCH v3 07/16] x86/kvm/emulate: Introduce EM_ASM_1SRC2

On Wed, Jul 23, 2025 at 05:16:38PM -0700, Sean Christopherson wrote:
> For all of the KVM patches, please use
> 
>   KVM: x86:
> 
> "x86/kvm" is used for guest-side code, and while I hope no one will conflate this
> with guest code, the consistency is helpful.

Sure.

> On Mon, Jul 14, 2025, Peter Zijlstra wrote:
> > Replace the FASTOP1SRC2*() instructions.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > ---
> >  arch/x86/kvm/emulate.c |   34 ++++++++++++++++++++++++++--------
> >  1 file changed, 26 insertions(+), 8 deletions(-)
> > 
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -317,6 +317,24 @@ static int em_##op(struct x86_emulate_ct
> >  	ON64(case 8: __EM_ASM_1(op##q, rax); break;) \
> >  	EM_ASM_END
> >  
> > +/* 1-operand, using "c" (src2) */
> > +#define EM_ASM_1SRC2(op, name) \
> > +	EM_ASM_START(name) \
> > +	case 1: __EM_ASM_1(op##b, cl); break; \
> > +	case 2: __EM_ASM_1(op##w, cx); break; \
> > +	case 4: __EM_ASM_1(op##l, ecx); break; \
> > +	ON64(case 8: __EM_ASM_1(op##q, rcx); break;) \
> > +	EM_ASM_END
> > +
> > +/* 1-operand, using "c" (src2) with exception */
> > +#define EM_ASM_1SRC2EX(op, name) \
> > +	EM_ASM_START(name) \
> > +	case 1: __EM_ASM_1_EX(op##b, cl); break; \
> > +	case 2: __EM_ASM_1_EX(op##w, cx); break; \
> > +	case 4: __EM_ASM_1_EX(op##l, ecx); break; \
> > +	ON64(case 8: __EM_ASM_1(op##q, rcx); break;) \
> 
> This needs to be __EM_ASM_1_EX().  Luckily, KVM-Unit-Tests actually has testcase
> for divq (somewhere in the morass of testcases).  I also now have an extension to
> the fastops selftest to explicitly test all four flavors of div-by-zero; I'll get
> it posted tomorrow.
> 
> (also, don't also me how long it took me to spot the copy+paste typo; I was full
>  on debugging the exception fixup code before I realized my local diff looked
>  "odd", *sigh*)

Urgh, sorry about that. Typically I use regex for these things, clearly
I messed up here.

Thanks and fixed!