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, 26 Feb 2020 17:28:11 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Andy Lutomirski <luto@amacapital.net>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Brian Gerst <brgerst@gmail.com>,
        Juergen Gross <jgross@suse.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>
Subject: Re: [patch 13/16] x86/entry: Move irqflags and context tracking to C
 for simple idtentries
Message-ID: <20200226162811.GA18400@hirez.programming.kicks-ass.net>
References: <20200225223321.231477305@linutronix.de>
 <20200225224145.444611199@linutronix.de>
 <20200226080538.GO18400@hirez.programming.kicks-ass.net>
 <20200226092018.GR18400@hirez.programming.kicks-ass.net>
 <CALCETrXYbmrVvYQzBDp8YP+-UyF3KPDgcK__HuNmpdsMBJYDVA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALCETrXYbmrVvYQzBDp8YP+-UyF3KPDgcK__HuNmpdsMBJYDVA@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Feb 26, 2020 at 07:11:39AM -0800, Andy Lutomirski wrote:

> In some sense, this is a weakness of the magic macro approach.  Some
> of the entries just want to have code that runs before all the entry
> fixups.  This is an example of it.  So are the cr2 reads.  It can all
> be made to work, but it's a bit gross.

Right. In my current pile (new patche since last posting) I also have
one that makes #DB save-clear/restore DR7.

I got it early enough that only a watchpoint on the task stack can still
screw us over, since I also included your patch that excludes
cpu_entry_area.

Pushing it earlier still would require calling into C from the entry
stack, which I know is on your todo list, but we're not quite there yet.