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Message-ID: <20170809093511.oorxaiau5dtgfjxr@hirez.programming.kicks-ass.net>
Date: Wed, 9 Aug 2017 11:35:11 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Juergen Gross <jgross@...e.com>
Cc: Andy Lutomirski <luto@...nel.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
"x86@...nel.org" <x86@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
Jiri Slaby <jslaby@...e.cz>, Ingo Molnar <mingo@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>, Mike Galbraith <efault@....de>
Subject: Re: [PATCH v4 1/2] x86/unwind: add ORC unwinder
On Wed, Aug 09, 2017 at 11:24:07AM +0200, Juergen Gross wrote:
> On 09/08/17 11:16, Peter Zijlstra wrote:
> > On Wed, Aug 09, 2017 at 10:49:43AM +0200, Juergen Gross wrote:
> >>> ALTERNATIVE "pushfq; popq %rax", "callq *pv_irq_ops.save_fl",
> >>> X86_FEATURE_GODDAMN_PV_IRQ_OPS
> >>
> >> You are aware that at least some of the Xen irq pvops functionality is
> >> patched inline? Your modification would slow down pv guests quite a
> >> bit, I guess.
> >
> > Where does that live? I know of the inline patching for native, but
> > didn't know the guests did any of that too.
>
> See arch/x86/xen/enlighten_pv.c xen_patch().
'obvious' name that :-) I see that the actual code that's patched in
lives in xen-asm.S which unlike the native case doesn't appear to have
its own section. So that might make things even more difficult.
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