linux-kernel - Re: [PATCH v8 02/28] x86/boot: Relocate definition of the initial state of CR0

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Date:   Wed, 30 Aug 2017 21:04:18 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liang Z Li <liang.z.li@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Andy Lutomirski <luto@...capital.net>,
        Dave Hansen <dave.hansen@...el.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v8 02/28] x86/boot: Relocate definition of the initial
 state of CR0

On Fri, 2017-08-25 at 19:41 +0200, Borislav Petkov wrote:

Thanks Borislav for your feedback!

> On Fri, Aug 18, 2017 at 05:27:43PM -0700, Ricardo Neri wrote:
> > Both head_32.S and head_64.S utilize the same value to initialize the
> > control register CR0. Also, other parts of the kernel might want to access
> > to this initial definition (e.g., emulation code for User-Mode Instruction
> 
> s/to //
> 
> > Prevention uses this state to provide a sane dummy value for CR0 when

I'll make this change.

> > emulating the smsw instruction). Thus, relocate this definition to a
> > header file from which it can be conveniently accessed.
> > 
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Andy Lutomirski <luto@...capital.net>
> > Cc: Andy Lutomirski <luto@...nel.org>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: Brian Gerst <brgerst@...il.com>
> > Cc: Dave Hansen <dave.hansen@...el.com>
> > Cc: Denys Vlasenko <dvlasenk@...hat.com>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: linux-arch@...r.kernel.org
> > Cc: linux-mm@...ck.org
> > Suggested-by: Borislav Petkov <bp@...en8.de>
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> > ---
> >  arch/x86/include/uapi/asm/processor-flags.h | 6 ++++++
> >  arch/x86/kernel/head_32.S                   | 3 ---
> >  arch/x86/kernel/head_64.S                   | 3 ---
> >  3 files changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
> > index 185f3d10c194..aae1f2aa7563 100644
> > --- a/arch/x86/include/uapi/asm/processor-flags.h
> > +++ b/arch/x86/include/uapi/asm/processor-flags.h
> > @@ -151,5 +151,11 @@
> >  #define CX86_ARR_BASE	0xc4
> >  #define CX86_RCR_BASE	0xdc
> >  
> > +/*
> > + * Initial state of CR0 for head_32/64.S
> > + */
> 
> No need for that comment.
> 
> With the minor nitpicks addressed, you can add:
> 
> Reviewed-by: Borislav Petkov <bp@...e.de>

Thank you! Is it necessary for me to submit a v9 with these updates?
Perhaps I can make these updates in branch for the maintainers to pull
when/if this series is ack'ed.

Thanks and BR,
Ricardo