Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752133AbdF3NLw (ORCPT ); Fri, 30 Jun 2017 09:11:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42928 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751668AbdF3NLv (ORCPT ); Fri, 30 Jun 2017 09:11:51 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6383980463 Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jpoimboe@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 6383980463 Date: Fri, 30 Jun 2017 08:11:48 -0500 From: Josh Poimboeuf To: Andy Lutomirski Cc: X86 ML , "linux-kernel@vger.kernel.org" , live-patching@vger.kernel.org, Linus Torvalds , Jiri Slaby , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Mike Galbraith Subject: Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Message-ID: <20170630131148.yszdjakekrwqlf6k@treble> References: <20170629175333.bicpvbwo4d5pdbak@treble> <20170629190559.ttw52ahwtsjynayx@treble> <20170629214134.c36krjhvzegwkfjk@treble> <20170630021249.cqkszxaqtwakmzpg@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 30 Jun 2017 13:11:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1996 Lines: 54 On Thu, Jun 29, 2017 at 10:41:44PM -0700, Andy Lutomirski wrote: > On Thu, Jun 29, 2017 at 10:05 PM, Andy Lutomirski wrote: > > Hmm. There's another option that might be considerably nicer, though: > > put the IRQ stack at a known (at link time) position *in percpu > > space*. (Presumably it already is -- I haven't checked.) Then we do: > > > > .macro ENTER_IRQ_STACK old_rsp > > DEBUG_ENTRY_ASSERT_IRQS_OFF > > movq %rsp, \old_rsp > > incl PER_CPU_VAR(irq_count) > > > > /* > > * Right now, if we just incremented irq_count to zero, we've > > * claimed the IRQ stack but we haven't switched to it yet. > > * Anything that can interrupt us here without using IST > > * must be *extremely* careful to limit its stack usage. > > */ > > jnz .Lpush_old_rsp_\@ > > movq \old_rsp, PER_CPU_VAR(top_word_in_irq_stack) > > movq PER_CPU_VAR(irq_stack_ptr), %rsp > > .Lpush_old_rsp_\@: > > pushq \old_rsp > > .endm > > > > How about the two commits here (well, soon to be there once gitweb catches up): > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=0f56a55bb133cd53ccb78ca51378086296618322 > > If you like them, want to add them to your series? The second patch looks good to me, thanks. I can pick up the patches. A few comments about the first patch: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=3e2aa2102cc1c5e60d4a8637bff78d0478a55059 - It uses a '693:' label instead of '.Lirqs_off_\@:' - There's a comment I don't follow: "Anything that can interrupt us here without using IST must be *extremely* careful to limit its stack usage." What specifically could interrupt there without using IST? - Since do_softirq_own_stack() is a callable function, I think it still needs to save rbp. - Why change the "jmp error_exit" to "ret" in xen_do_hypervisor_callback()? -- Josh