From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7EC0FC4361B for ; Wed, 9 Dec 2020 13:28:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5157723B45 for ; Wed, 9 Dec 2020 13:28:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732384AbgLIN2d (ORCPT ); Wed, 9 Dec 2020 08:28:33 -0500 Received: from foss.arm.com ([217.140.110.172]:34654 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732358AbgLIN2G (ORCPT ); Wed, 9 Dec 2020 08:28:06 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6032831B; Wed, 9 Dec 2020 05:27:20 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.26.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2F7983F66B; Wed, 9 Dec 2020 05:27:17 -0800 (PST) Date: Wed, 9 Dec 2020 13:27:10 +0000 From: Mark Rutland To: Andy Lutomirski Cc: =?utf-8?B?SsO8cmdlbiBHcm/Dnw==?= , Peter Zijlstra , Stefano Stabellini , "VMware, Inc." , X86 ML , LKML , Linux Virtualization , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , xen-devel , Thomas Gleixner , Boris Ostrovsky Subject: Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf Message-ID: <20201209132710.GA8566@C02TD0UTHF1T.local> References: <20201120114630.13552-1-jgross@suse.com> <20201120114630.13552-6-jgross@suse.com> <20201120115943.GD3021@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 22, 2020 at 01:44:53PM -0800, Andy Lutomirski wrote: > On Sat, Nov 21, 2020 at 10:55 PM Jürgen Groß wrote: > > > > On 20.11.20 12:59, Peter Zijlstra wrote: > > > On Fri, Nov 20, 2020 at 12:46:23PM +0100, Juergen Gross wrote: > > >> +static __always_inline void arch_local_irq_restore(unsigned long flags) > > >> +{ > > >> + if (!arch_irqs_disabled_flags(flags)) > > >> + arch_local_irq_enable(); > > >> +} > > > > > > If someone were to write horrible code like: > > > > > > local_irq_disable(); > > > local_irq_save(flags); > > > local_irq_enable(); > > > local_irq_restore(flags); > > > > > > we'd be up some creek without a paddle... now I don't _think_ we have > > > genius code like that, but I'd feel saver if we can haz an assertion in > > > there somewhere... > > > > > > Maybe something like: > > > > > > #ifdef CONFIG_DEBUG_ENTRY // for lack of something saner > > > WARN_ON_ONCE((arch_local_save_flags() ^ flags) & X86_EFLAGS_IF); > > > #endif > > > > > > At the end? > > > > I'd like to, but using WARN_ON_ONCE() in include/asm/irqflags.h sounds > > like a perfect receipt for include dependency hell. > > > > We could use a plain asm("ud2") instead. > > How about out-of-lining it: > > #ifdef CONFIG_DEBUG_ENTRY > extern void warn_bogus_irqrestore(); > #endif > > static __always_inline void arch_local_irq_restore(unsigned long flags) > { > if (!arch_irqs_disabled_flags(flags)) { > arch_local_irq_enable(); > } else { > #ifdef CONFIG_DEBUG_ENTRY > if (unlikely(arch_local_irq_save() & X86_EFLAGS_IF)) > warn_bogus_irqrestore(); > #endif > } I was just talking to Peter on IRC about implementing the same thing for arm64, so could we put this in the generic irqflags code? IIUC we can use raw_irqs_disabled() to do the check. As this isn't really entry specific (and IIUC the cases this should catch would break lockdep today), maybe we should add a new DEBUG_IRQFLAGS for this, that DEBUG_LOCKDEP can also select? Something like: #define local_irq_restore(flags) \ do { \ if (!raw_irqs_disabled_flags(flags)) { \ trace_hardirqs_on(); \ } else if (IS_ENABLED(CONFIG_DEBUG_IRQFLAGS) { \ if (unlikely(raw_irqs_disabled()) \ warn_bogus_irqrestore(); \ } \ raw_local_irq_restore(flags); \ } while (0) ... perhaps? (ignoring however we deal with once-ness). Thanks, Mark. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BFB8C433FE for ; Wed, 9 Dec 2020 13:27:24 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 13ED823BC7 for ; Wed, 9 Dec 2020 13:27:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 13ED823BC7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=virtualization-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id ACB8087864; Wed, 9 Dec 2020 13:27:23 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id d6X+h62nkEZa; Wed, 9 Dec 2020 13:27:22 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id DC736877D5; Wed, 9 Dec 2020 13:27:22 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id A2AC9C0893; Wed, 9 Dec 2020 13:27:22 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id E401AC013B for ; Wed, 9 Dec 2020 13:27:21 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id DFDA786329 for ; Wed, 9 Dec 2020 13:27:21 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id PzMitFLWNEKz for ; Wed, 9 Dec 2020 13:27:20 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by fraxinus.osuosl.org (Postfix) with ESMTP id D4A73861F6 for ; Wed, 9 Dec 2020 13:27:20 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6032831B; Wed, 9 Dec 2020 05:27:20 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.26.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2F7983F66B; Wed, 9 Dec 2020 05:27:17 -0800 (PST) Date: Wed, 9 Dec 2020 13:27:10 +0000 From: Mark Rutland To: Andy Lutomirski Subject: Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf Message-ID: <20201209132710.GA8566@C02TD0UTHF1T.local> References: <20201120114630.13552-1-jgross@suse.com> <20201120114630.13552-6-jgross@suse.com> <20201120115943.GD3021@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: =?utf-8?B?SsO8cmdlbiBHcm/Dnw==?= , Stefano Stabellini , Peter Zijlstra , X86 ML , LKML , Linux Virtualization , "VMware, Inc." , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , xen-devel , Thomas Gleixner , Boris Ostrovsky X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" T24gU3VuLCBOb3YgMjIsIDIwMjAgYXQgMDE6NDQ6NTNQTSAtMDgwMCwgQW5keSBMdXRvbWlyc2tp IHdyb3RlOgo+IE9uIFNhdCwgTm92IDIxLCAyMDIwIGF0IDEwOjU1IFBNIErDvHJnZW4gR3Jvw58g PGpncm9zc0BzdXNlLmNvbT4gd3JvdGU6Cj4gPgo+ID4gT24gMjAuMTEuMjAgMTI6NTksIFBldGVy IFppamxzdHJhIHdyb3RlOgo+ID4gPiBPbiBGcmksIE5vdiAyMCwgMjAyMCBhdCAxMjo0NjoyM1BN ICswMTAwLCBKdWVyZ2VuIEdyb3NzIHdyb3RlOgo+ID4gPj4gK3N0YXRpYyBfX2Fsd2F5c19pbmxp bmUgdm9pZCBhcmNoX2xvY2FsX2lycV9yZXN0b3JlKHVuc2lnbmVkIGxvbmcgZmxhZ3MpCj4gPiA+ PiArewo+ID4gPj4gKyAgICBpZiAoIWFyY2hfaXJxc19kaXNhYmxlZF9mbGFncyhmbGFncykpCj4g PiA+PiArICAgICAgICAgICAgYXJjaF9sb2NhbF9pcnFfZW5hYmxlKCk7Cj4gPiA+PiArfQo+ID4g Pgo+ID4gPiBJZiBzb21lb25lIHdlcmUgdG8gd3JpdGUgaG9ycmlibGUgY29kZSBsaWtlOgo+ID4g Pgo+ID4gPiAgICAgICBsb2NhbF9pcnFfZGlzYWJsZSgpOwo+ID4gPiAgICAgICBsb2NhbF9pcnFf c2F2ZShmbGFncyk7Cj4gPiA+ICAgICAgIGxvY2FsX2lycV9lbmFibGUoKTsKPiA+ID4gICAgICAg bG9jYWxfaXJxX3Jlc3RvcmUoZmxhZ3MpOwo+ID4gPgo+ID4gPiB3ZSdkIGJlIHVwIHNvbWUgY3Jl ZWsgd2l0aG91dCBhIHBhZGRsZS4uLiBub3cgSSBkb24ndCBfdGhpbmtfIHdlIGhhdmUKPiA+ID4g Z2VuaXVzIGNvZGUgbGlrZSB0aGF0LCBidXQgSSdkIGZlZWwgc2F2ZXIgaWYgd2UgY2FuIGhheiBh biBhc3NlcnRpb24gaW4KPiA+ID4gdGhlcmUgc29tZXdoZXJlLi4uCj4gPiA+Cj4gPiA+IE1heWJl IHNvbWV0aGluZyBsaWtlOgo+ID4gPgo+ID4gPiAjaWZkZWYgQ09ORklHX0RFQlVHX0VOVFJZIC8v IGZvciBsYWNrIG9mIHNvbWV0aGluZyBzYW5lcgo+ID4gPiAgICAgICBXQVJOX09OX09OQ0UoKGFy Y2hfbG9jYWxfc2F2ZV9mbGFncygpIF4gZmxhZ3MpICYgWDg2X0VGTEFHU19JRik7Cj4gPiA+ICNl bmRpZgo+ID4gPgo+ID4gPiBBdCB0aGUgZW5kPwo+ID4KPiA+IEknZCBsaWtlIHRvLCBidXQgdXNp bmcgV0FSTl9PTl9PTkNFKCkgaW4gaW5jbHVkZS9hc20vaXJxZmxhZ3MuaCBzb3VuZHMKPiA+IGxp a2UgYSBwZXJmZWN0IHJlY2VpcHQgZm9yIGluY2x1ZGUgZGVwZW5kZW5jeSBoZWxsLgo+ID4KPiA+ IFdlIGNvdWxkIHVzZSBhIHBsYWluIGFzbSgidWQyIikgaW5zdGVhZC4KPiAKPiBIb3cgYWJvdXQg b3V0LW9mLWxpbmluZyBpdDoKPiAKPiAjaWZkZWYgQ09ORklHX0RFQlVHX0VOVFJZCj4gZXh0ZXJu IHZvaWQgd2Fybl9ib2d1c19pcnFyZXN0b3JlKCk7Cj4gI2VuZGlmCj4gCj4gc3RhdGljIF9fYWx3 YXlzX2lubGluZSB2b2lkIGFyY2hfbG9jYWxfaXJxX3Jlc3RvcmUodW5zaWduZWQgbG9uZyBmbGFn cykKPiB7Cj4gICAgICAgIGlmICghYXJjaF9pcnFzX2Rpc2FibGVkX2ZsYWdzKGZsYWdzKSkgewo+ ICAgICAgICAgICAgICAgIGFyY2hfbG9jYWxfaXJxX2VuYWJsZSgpOwo+ICAgICAgICB9IGVsc2Ug ewo+ICNpZmRlZiBDT05GSUdfREVCVUdfRU5UUlkKPiAgICAgICAgICAgICAgICBpZiAodW5saWtl bHkoYXJjaF9sb2NhbF9pcnFfc2F2ZSgpICYgWDg2X0VGTEFHU19JRikpCj4gICAgICAgICAgICAg ICAgICAgICB3YXJuX2JvZ3VzX2lycXJlc3RvcmUoKTsKPiAjZW5kaWYKPiB9CgpJIHdhcyBqdXN0 IHRhbGtpbmcgdG8gUGV0ZXIgb24gSVJDIGFib3V0IGltcGxlbWVudGluZyB0aGUgc2FtZSB0aGlu ZyBmb3IKYXJtNjQsIHNvIGNvdWxkIHdlIHB1dCB0aGlzIGluIHRoZSBnZW5lcmljIGlycWZsYWdz IGNvZGU/IElJVUMgd2UgY2FuCnVzZSByYXdfaXJxc19kaXNhYmxlZCgpIHRvIGRvIHRoZSBjaGVj ay4KCkFzIHRoaXMgaXNuJ3QgcmVhbGx5IGVudHJ5IHNwZWNpZmljIChhbmQgSUlVQyB0aGUgY2Fz ZXMgdGhpcyBzaG91bGQKY2F0Y2ggd291bGQgYnJlYWsgbG9ja2RlcCB0b2RheSksIG1heWJlIHdl IHNob3VsZCBhZGQgYSBuZXcKREVCVUdfSVJRRkxBR1MgZm9yIHRoaXMsIHRoYXQgREVCVUdfTE9D S0RFUCBjYW4gYWxzbyBzZWxlY3Q/CgpTb21ldGhpbmcgbGlrZToKCiNkZWZpbmUgbG9jYWxfaXJx X3Jlc3RvcmUoZmxhZ3MpICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIFwKICAgICAgIGRv IHsgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgXAog ICAgICAgICAgICAgICBpZiAoIXJhd19pcnFzX2Rpc2FibGVkX2ZsYWdzKGZsYWdzKSkgeyAgICAg ICAgICBcCiAgICAgICAgICAgICAgICAgICAgICAgdHJhY2VfaGFyZGlycXNfb24oKTsgICAgICAg ICAgICAgICAgICAgIFwKICAgICAgICAgICAgICAgfSBlbHNlIGlmIChJU19FTkFCTEVEKENPTkZJ R19ERUJVR19JUlFGTEFHUykgeyAgXAogICAgICAgICAgICAgICAgICAgICAgIGlmICh1bmxpa2Vs eShyYXdfaXJxc19kaXNhYmxlZCgpKSAgICAgICBcCiAgICAgICAgICAgICAgICAgICAgICAgICAg ICAgICB3YXJuX2JvZ3VzX2lycXJlc3RvcmUoKTsgICAgICAgIFwKICAgICAgICAgICAgICAgfSAg ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgXAogICAgICAgICAg ICAgICByYXdfbG9jYWxfaXJxX3Jlc3RvcmUoZmxhZ3MpOyAgICAgICAgICAgICAgICAgICBcCiAg ICAgICAgfSB3aGlsZSAoMCkKCi4uLiBwZXJoYXBzPyAoaWdub3JpbmcgaG93ZXZlciB3ZSBkZWFs IHdpdGggb25jZS1uZXNzKS4KClRoYW5rcywKTWFyay4KX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX18KVmlydHVhbGl6YXRpb24gbWFpbGluZyBsaXN0ClZpcnR1 YWxpemF0aW9uQGxpc3RzLmxpbnV4LWZvdW5kYXRpb24ub3JnCmh0dHBzOi8vbGlzdHMubGludXhm b3VuZGF0aW9uLm9yZy9tYWlsbWFuL2xpc3RpbmZvL3ZpcnR1YWxpemF0aW9u