linux-kernel - Re: [PATCH v4 1/2] x86/unwind: add ORC unwinder

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Message-ID: <29fcd05f-3a0d-c20e-f20a-ee2019eea73c@suse.com>
Date:   Wed, 9 Aug 2017 11:24:07 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 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().


Juergen