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;
From:   Nadav Amit <nadav.amit@gmail.com>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\))
Subject: x86: CR4 update when IRQs are enabled
Message-Id: <E7DBFC7E-3904-483A-89E1-56EC17F14EF1@gmail.com>
Date:   Wed, 8 Nov 2017 13:52:17 -0800
To:     LKML <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

I am puzzled by the comment in tlb_state.cr4 , which says:

        /*
         * Access to this CR4 shadow and to H/W CR4 is protected by
         * disabling interrupts when modifying either one.
         */

This does not seem to be true and adding a warning to CR4 writes when
!irqs_disabled() immediately fires in identify_cpu() and
__mcheck_cpu_init_generic(). While these two are called during boot, I think
there other CR4 changes with enabled IRQs, for example, PR_SET_TSC.

So my question(s): Is the comment correct? Is the current behavior correct?

Thanks,
Nadav

From 1584246670768136781@xxx Thu Nov 16 18:02:40 +0000 2017
X-GM-THRID: 1584246670768136781
X-Gmail-Labels: Inbox,Category Promotions,HistoricalUnread