linux-kernel - Re: [patch V2 08/17] x86/entry: Move syscall irq tracing to C code

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Date:   Thu, 24 Oct 2019 19:40:44 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Will Deacon <will@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [patch V2 08/17] x86/entry: Move syscall irq tracing to C code

On Thu, Oct 24, 2019 at 09:24:13AM -0700, Andy Lutomirski wrote:
> On Wed, Oct 23, 2019 at 2:30 PM Andy Lutomirski <luto@...nel.org> wrote:
> >
> > On Wed, Oct 23, 2019 at 5:31 AM Thomas Gleixner <tglx@...utronix.de> wrote:
> > >
> > > Interrupt state tracing can be safely done in C code. The few stack
> > > operations in assembly do not need to be covered.
> > >
> > > Remove the now pointless indirection via .Lsyscall_32_done and jump to
> > > swapgs_restore_regs_and_return_to_usermode directly.
> >
> > This doesn't look right.
> 
> Well, I feel a bit silly.  I read this:
> 
> >
> > >  #define SYSCALL_EXIT_WORK_FLAGS                                \
> > > @@ -279,6 +282,9 @@ static void syscall_slow_exit_work(struc
> 
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> and I applied the diff in my head to the wrong function, and I didn't
> notice that it didn't really apply there.  Oddly, gitweb gets this

I had the same when reviewing these patches; I was almost going to ask
tglx about it on IRC when the penny dropped.