Re: [PATCH 03/19] x86/cpufeatures: Enable CET CR4 bit for shadow stack

From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "peterz@infradead.org" <peterz@infradead.org>,
	"Yang, Weijiang" <weijiang.yang@intel.com>
Cc: "keescook@chromium.org" <keescook@chromium.org>, "Christopherson,,
	Sean" <seanjc@google.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 03/19] x86/cpufeatures: Enable CET CR4 bit for shadow stack
Date: Thu, 16 Jun 2022 17:12:47 +0000	[thread overview]
Message-ID: <ca4e04f2dcc33849ebb9bf128f6ff632b5ffe747.camel@intel.com> (raw)
In-Reply-To: <YqsEyoaxPFpZcolP@hirez.programming.kicks-ass.net>

On Thu, 2022-06-16 at 12:24 +0200, Peter Zijlstra wrote:
> On Thu, Jun 16, 2022 at 04:46:27AM -0400, Yang Weijiang wrote:
> > --- a/arch/x86/include/asm/cpu.h
> > +++ b/arch/x86/include/asm/cpu.h
> > @@ -74,7 +74,7 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
> >   static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {}
> >   #endif
> >   
> > -extern __noendbr void cet_disable(void);
> > +extern __noendbr void ibt_disable(void);
> >   
> >   struct ucode_cpu_info;
> >   
> > diff --git a/arch/x86/kernel/cpu/common.c
> > b/arch/x86/kernel/cpu/common.c
> > index c296cb1c0113..86102a8d451e 100644
> > --- a/arch/x86/kernel/cpu/common.c
> > +++ b/arch/x86/kernel/cpu/common.c
> > @@ -598,23 +598,23 @@ __noendbr void ibt_restore(u64 save)
> >   
> > -__noendbr void cet_disable(void)
> > +__noendbr void ibt_disable(void)
> >   {
> >        if (cpu_feature_enabled(X86_FEATURE_IBT))
> >                wrmsrl(MSR_IA32_S_CET, 0);
> 
> Not sure about this rename; it really disables all of (S) CET.
> 
> Specifically, once we do S-SHSTK (after FRED) we might also very much
> need to kill that for kexec.

Sure, what about something like sup_cet_disable()?