linux-kernel - Re: [patch 13/16] x86/entry: Move irqflags and context tracking to C for simple idtentries

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Date:   Wed, 26 Feb 2020 17:28:11 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [patch 13/16] x86/entry: Move irqflags and context tracking to C
 for simple idtentries

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.