linux-kernel - Re: [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on error

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Message-ID: <CALCETrVaCZKjXj9ZqtvQgLk2DqXwNCh7b5DHvSnNAORsqJXCcQ@mail.gmail.com>
Date:   Thu, 21 Mar 2019 11:20:52 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Jan Beulich <jbeulich@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Joel Fernandes <joel@...lfernandes.org>,
        He Zhe <zhe.he@...driver.com>
Subject: Re: [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on error_entry

On Thu, Mar 21, 2019 at 11:19 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Thu, Mar 21, 2019 at 11:05 AM Andy Lutomirski <luto@...capital.net> wrote:
> >
> > In the long run, I think the right solution is to rewrite even more of
> > this mess in C.  We really ought to be able to put the IRQ flag
> > tracing and the context tracking into C code.
>
> Tangentially about this long run thing - can we start discussing just
> dropping PV mode entirely in the long run? Or even not-so-long run?
>
> What are the pressing advantages of paravirt these days? Because I can
> point to a lot of pressing _disadvantages_, and not all of them are
> about more complex code as shown by this patch...
>

I dunno.  Lots of people at least use to have serious commercial interest in it.

Hey Xen folks, how close are we to being able to say "if you want to
run a new kernel, you need to switch to PVH or similar"?

--Andy