Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 10 Jul 2019 22:02:40 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Xi Ruoyao <xry111@mengyan1223.wang>,
        Jiri Kosina <jikos@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Borislav Petkov <bp@alien8.de>, Len Brown <lenb@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Bob Moore <robert.moore@intel.com>,
        Erik Schmauss <erik.schmauss@intel.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH] x86/asm: Move native_write_cr0/3() out of line
Message-ID: <20190710200240.GR3402@hirez.programming.kicks-ass.net>
References: <cb6d381ed7cd0bf732ae9d8f30c806b849b0f94b.camel@mengyan1223.wang>
 <alpine.DEB.2.21.1907101404570.1758@nanos.tec.linutronix.de>
 <nycvar.YFH.7.76.1907101425290.5899@cbobk.fhfr.pm>
 <768463eb26a2feb0fcc374fd7f9cc28b96976917.camel@mengyan1223.wang>
 <20190710134433.GN3402@hirez.programming.kicks-ass.net>
 <nycvar.YFH.7.76.1907101621050.5899@cbobk.fhfr.pm>
 <20190710142653.GJ3419@hirez.programming.kicks-ass.net>
 <alpine.DEB.2.21.1907101709340.1758@nanos.tec.linutronix.de>
 <a822cf447949582e2a11b7899f22b11da02f0ece.camel@mengyan1223.wang>
 <alpine.DEB.2.21.1907102140340.1758@nanos.tec.linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.21.1907102140340.1758@nanos.tec.linutronix.de>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jul 10, 2019 at 09:42:46PM +0200, Thomas Gleixner wrote:
> The pinning of sensitive CR0 and CR4 bits caused a boot crash when loading
> the kvm_intel module on a kernel compiled with CONFIG_PARAVIRT=n.
> 
> The reason is that the static key which controls the pinning is marked RO
> after init. The kvm_intel module contains a CR4 write which requires to
> update the static key entry list. That obviously does not work when the key
> is in a RO section.
> 
> With CONFIG_PARAVIRT enabled this does not happen because the CR4 write
> uses the paravirt indirection and the actual write function is built in.
> 
> As the key is intended to be immutable after init, move
> native_write_cr0/3() out of line.
> 
> While at it consolidate the update of the cr4 shadow variable and store the
> value right away when the pinning is initialized on a booting CPU. No point
> in reading it back 20 instructions later. This allows to confine the static
> key and the pinning variable to cpu/common and allows to mark them static.
> 
> Fixes: 8dbec27a242c ("x86/asm: Pin sensitive CR0 bits")
> Fixes: 873d50d58f67 ("x86/asm: Pin sensitive CR4 bits")
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Reported-by: Xi Ruoyao <xry111@mengyan1223.wang>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Xi Ruoyao <xry111@mengyan1223.wang>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>