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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 65EFBC63697 for ; Mon, 23 Nov 2020 05:22:36 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 E7128207FF for ; Mon, 23 Nov 2020 05:22:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="hp03zaAa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E7128207FF Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.33606.64718 (Exim 4.92) (envelope-from ) id 1kh4Ic-0006H8-2b; Mon, 23 Nov 2020 05:22:02 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 33606.64718; Mon, 23 Nov 2020 05:22:02 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kh4Ib-0006Gz-Rh; Mon, 23 Nov 2020 05:22:01 +0000 Received: by outflank-mailman (input) for mailman id 33606; Mon, 23 Nov 2020 05:22:00 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kh4Ia-0006Gu-C2 for xen-devel@lists.xenproject.org; Mon, 23 Nov 2020 05:22:00 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 3290cf00-ff34-4a28-ab2e-3f70a4a07943; Mon, 23 Nov 2020 05:21:58 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C30A0AC0C; Mon, 23 Nov 2020 05:21:57 +0000 (UTC) Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kh4Ia-0006Gu-C2 for xen-devel@lists.xenproject.org; Mon, 23 Nov 2020 05:22:00 +0000 X-Inumbo-ID: 3290cf00-ff34-4a28-ab2e-3f70a4a07943 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 3290cf00-ff34-4a28-ab2e-3f70a4a07943; Mon, 23 Nov 2020 05:21:58 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1606108917; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=bnlvBaRBDOwhFV9Frw/ljad6M3emL9wmQHU9HFSgjyg=; b=hp03zaAa6g9jzr7ZFVJcK9sSTowRPcxkxQEe9lmU/Iow1G3DAlxUFBpvBVKmZJWewAUzYp vGYrU8C7R3DG7nHlXCVKch/x7KxTgOIiJvaA3kRKTaVRHf6CnXlZA3TTNnQV9qi0tFvy5H GAR5vu9087dpuD1Mp71uPoXjdE0aTbI= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C30A0AC0C; Mon, 23 Nov 2020 05:21:57 +0000 (UTC) To: Andy Lutomirski Cc: Peter Zijlstra , Stefano Stabellini , "VMware, Inc." , X86 ML , LKML , Linux Virtualization , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , xen-devel , Thomas Gleixner , Boris Ostrovsky References: <20201120114630.13552-1-jgross@suse.com> <20201120114630.13552-6-jgross@suse.com> <20201120115943.GD3021@hirez.programming.kicks-ass.net> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Subject: Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf Message-ID: <894a4cec-8426-4152-d391-474711040c5b@suse.com> Date: Mon, 23 Nov 2020 06:21:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KjjwiwVOCYamlMPkg53LvZQjNAFZkdRhT" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --KjjwiwVOCYamlMPkg53LvZQjNAFZkdRhT Content-Type: multipart/mixed; boundary="PYEGjNEoNCwI2vygBQpmaIoVRT2ThJktq"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Andy Lutomirski Cc: Peter Zijlstra , Stefano Stabellini , "VMware, Inc." , X86 ML , LKML , Linux Virtualization , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , xen-devel , Thomas Gleixner , Boris Ostrovsky Message-ID: <894a4cec-8426-4152-d391-474711040c5b@suse.com> Subject: Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf References: <20201120114630.13552-1-jgross@suse.com> <20201120114630.13552-6-jgross@suse.com> <20201120115943.GD3021@hirez.programming.kicks-ass.net> In-Reply-To: --PYEGjNEoNCwI2vygBQpmaIoVRT2ThJktq Content-Type: multipart/mixed; boundary="------------61EFA80FF3AEF2DEA88EC6CD" Content-Language: en-US This is a multi-part message in MIME format. --------------61EFA80FF3AEF2DEA88EC6CD Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 22.11.20 22:44, Andy Lutomirski wrote: > On Sat, Nov 21, 2020 at 10:55 PM J=C3=BCrgen Gro=C3=9F 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 fl= ags) >>>> +{ >>>> + 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. >=20 > How about out-of-lining it: >=20 > #ifdef CONFIG_DEBUG_ENTRY > extern void warn_bogus_irqrestore(); > #endif >=20 > 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 > } >=20 This couldn't be a WARN_ON_ONCE() then (or it would be a catch all). Another approach might be to open-code the WARN_ON_ONCE(), like: #ifdef CONFIG_DEBUG_ENTRY extern void warn_bogus_irqrestore(bool *once); #endif static __always_inline void arch_local_irq_restore(unsigned long flags) { if (!arch_irqs_disabled_flags(flags)) arch_local_irq_enable(); #ifdef CONFIG_DEBUG_ENTRY { static bool once; if (unlikely(arch_local_irq_save() & X86_EFLAGS_IF)) warn_bogus_irqrestore(&once); } #endif } Juergen --------------61EFA80FF3AEF2DEA88EC6CD Content-Type: application/pgp-keys; name="OpenPGP_0xB0DE9DD628BF132F.asc" Content-Transfer-Encoding: quoted-printable Content-Disposition: attachment; filename="OpenPGP_0xB0DE9DD628BF132F.asc" -----BEGIN PGP PUBLIC KEY BLOCK----- xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOBy= cWx w3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJvedYm8O= f8Z d621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJNwQpd369y= 9bf IhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvxXP3FAp2pkW0xq= G7/ 377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEBAAHNHEp1ZXJnZW4gR= 3Jv c3MgPGpnQHBmdXBmLm5ldD7CwHkEEwECACMFAlOMcBYCGwMHCwkIBwMCAQYVCAIJCgsEFgIDA= QIe AQIXgAAKCRCw3p3WKL8TL0KdB/93FcIZ3GCNwFU0u3EjNbNjmXBKDY4FUGNQH2lvWAUy+dnyT= hpw dtF/jQ6j9RwE8VP0+NXcYpGJDWlNb9/JmYqLiX2Q3TyevpB0CA3dbBQp0OW0fgCetToGIQrg0= MbD 1C/sEOv8Mr4NAfbauXjZlvTj30H2jO0u+6WGM6nHwbh2l5O8ZiHkH32iaSTfN7Eu5RnNVUJbv= oPH Z8SlM4KWm8rG+lIkGurqqu5gu8q8ZMKdsdGC4bBxdQKDKHEFExLJK/nRPFmAuGlId1E3fe10v= 5QL +qHI3EIPtyfE7i9Hz6rVwi7lWKgh7pe0ZvatAudZ+JNIlBKptb64FaiIOAWDCx1SzR9KdWVyZ= 2Vu IEdyb3NzIDxqZ3Jvc3NAc3VzZS5jb20+wsB5BBMBAgAjBQJTjHCvAhsDBwsJCAcDAgEGFQgCC= QoL BBYCAwECHgECF4AACgkQsN6d1ii/Ey/HmQf/RtI7kv5A2PS4RF7HoZhPVPogNVbC4YA6lW7Dr= Wf0 teC0RR3MzXfy6pJ+7KLgkqMlrAbN/8Dvjoz78X+5vhH/rDLa9BuZQlhFmvcGtCF8eR0T1v0nC= /nu AFVGy+67q2DH8As3KPu0344TBDpAvr2uYM4tSqxK4DURx5INz4ZZ0WNFHcqsfvlGJALDeE0Lh= ITT d9jLzdDad1pQSToCnLl6SBJZjDOX9QQcyUigZFtCXFst4dlsvddrxyqT1f17+2cFSdu7+ynLm= XBK 7abQ3rwJY8SbRO2iRulogc5vr/RLMMlscDAiDkaFQWLoqHHOdfO9rURssHNN8WkMnQfvUewRz= 80h SnVlcmdlbiBHcm9zcyA8amdyb3NzQG5vdmVsbC5jb20+wsB5BBMBAgAjBQJTjHDXAhsDBwsJC= AcD AgEGFQgCCQoLBBYCAwECHgECF4AACgkQsN6d1ii/Ey8PUQf/ehmgCI9jB9hlgexLvgOtf7PJn= FOX gMLdBQgBlVPO3/D9R8LtF9DBAFPNhlrsfIG/SqICoRCqUcJ96Pn3P7UUinFG/I0ECGF4EvTE1= jnD kfJZr6jrbjgyoZHiw/4BNwSTL9rWASyLgqlA8u1mf+c2yUwcGhgkRAd1gOwungxcwzwqgljf0= N51 N5JfVRHRtyfwq/ge+YEkDGcTU6Y0sPOuj4Dyfm8fJzdfHNQsWq3PnczLVELStJNdapwPOoE+l= otu fe3AM2vAEYJ9rTz3Cki4JFUsgLkHFqGZarrPGi1eyQcXeluldO3m91NK/1xMI3/+8jbO0tsn1= tqS EUGIJi7ox80eSnVlcmdlbiBHcm9zcyA8amdyb3NzQHN1c2UuZGU+wsB5BBMBAgAjBQJTjHDrA= hsD BwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQsN6d1ii/Ey+LhQf9GL45eU5vOowA2u5N3= g3O ZUEBmDHVVbqMtzwlmNC4k9Kx39r5s2vcFl4tXqW7g9/ViXYuiDXb0RfUpZiIUW89siKrkzmQ5= dM7 wRqzgJpJwK8Bn2MIxAKArekWpiCKvBOB/Cc+3EXE78XdlxLyOi/NrmSGRIov0karw2RzMNOu5= D+j LRZQd1Sv27AR+IP3I8U4aqnhLpwhK7MEy9oCILlgZ1QZe49kpcumcZKORmzBTNh30FVKK1Evm= V2x AKDoaEOgQB4iFQLhJCdP1I5aSgM5IVFdn7v5YgEYuJYx37IoN1EblHI//x/e2AaIHpzK5h88N= Eaw QsaNRpNSrcfbFmAg987ATQRTjHAWAQgAyzH6AOODMBjgfWE9VeCgsrwH3exNAU32gLq2xvjpW= nHI s98ndPUDpnoxWQugJ6MpMncr0xSwFmHEgnSEjK/PAjppgmyc57BwKII3sV4on+gDVFJR6Y8ZR= wgn BC5mVM6JjQ5xDk8WRXljExRfUX9pNhdE5eBOZJrDRoLUmmjDtKzWaDhIg/+1Hzz93X4fCQkNV= bVF LELU9bMaLPBG/x5q4iYZ2k2ex6d47YE1ZFdMm6YBYMOljGkZKwYde5ldM9mo45mmwe0icXKLk= pEd IXKTZeKDO+Hdv1aqFuAcccTg9RXDQjmwhC3yEmrmcfl0+rPghO0Iv3OOImwTEe4co3c1mwARA= QAB wsBfBBgBAgAJBQJTjHAWAhsMAAoJELDendYovxMvQ/gH/1ha96vm4P/L+bQpJwrZ/dneZcmEw= Tbe 8YFsw2V/Buv6Z4Mysln3nQK5ZadD534CF7TDVft7fC4tU4PONxF5D+/tvgkPfDAfF77zy2AH1= vJz Q1fOU8lYFpZXTXIHb+559UqvIB8AdgR3SAJGHHt4RKA0F7f5ipYBBrC6cyXJyyoprT10EMvU8= VGi wXvTyJz3fjoYsdFzpWPlJEBRMedCot60g5dmbdrZ5DWClAr0yau47zpWj3enf1tLWaqcsuylW= svi uGjKGw7KHQd3bxALOknAp4dN3QwBYCKuZ7AddY9yjynVaD5X7nF9nO5BjR/i1DG86lem3iBDX= zXs ZDn8R38=3D =3D2wuH -----END PGP PUBLIC KEY BLOCK----- --------------61EFA80FF3AEF2DEA88EC6CD-- --PYEGjNEoNCwI2vygBQpmaIoVRT2ThJktq-- --KjjwiwVOCYamlMPkg53LvZQjNAFZkdRhT Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature" -----BEGIN PGP SIGNATURE----- wsB5BAABCAAjFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAl+7RvQFAwAAAAAACgkQsN6d1ii/Ey8g cQf/Uld5d2rCAffpLFBdphaCOgFSPC2kdsNOxLyfO0gdHESNxsBoZ/BREBUVCnDawcH4cZlOl/6E ZHl1LQFfe963dpoB0V3n3hscAEalez4yzbsgsoysAqDqyA7Dl/kFW4ycGCnqtQCwK1utjoejDrWo JnODzWqm4fLZGbe1Y7VUw6G25XSL1mTfoXst86jeU0Ycvr6/NFBA4zFy10wAylyosZe/6xss9lKl f/GAwNiafJ6o8ZQwxAAh5vRf0oU0ro47p9Pu1wmzXNMfIO8TgazfvOp68Ml/0n4DR+TuCB1tarqx QqyidG1WLriURSEHtWCAmqiIgeagXTWcLkWsbGIImQ== =0xzm -----END PGP SIGNATURE----- --KjjwiwVOCYamlMPkg53LvZQjNAFZkdRhT--