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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 25699C47082 for ; Wed, 26 May 2021 16:06:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07D3A61284 for ; Wed, 26 May 2021 16:06:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235374AbhEZQHn (ORCPT ); Wed, 26 May 2021 12:07:43 -0400 Received: from mga05.intel.com ([192.55.52.43]:9170 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233270AbhEZQHl (ORCPT ); Wed, 26 May 2021 12:07:41 -0400 IronPort-SDR: 6Km/DnQpeImm89JIBFKsklp0iTirXQnY8PHur881BOiStksQh7PosHpqo23fUty8enQ1yvujdC cAviMlbWu5xA== X-IronPort-AV: E=McAfee;i="6200,9189,9996"; a="288082113" X-IronPort-AV: E=Sophos;i="5.82,331,1613462400"; d="scan'208";a="288082113" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 May 2021 09:06:07 -0700 IronPort-SDR: iscuW0DqtorPR2O6rHQL/gUAjGSPdOaJKlPkbgsqbOyxVXgUA4EKiYmsUu+n5yDX17/gw6js32 kZwmdl+LhPjA== X-IronPort-AV: E=Sophos;i="5.82,331,1613462400"; d="scan'208";a="480106463" Received: from sreddy2-mobl2.amr.corp.intel.com (HELO [10.255.229.59]) ([10.255.229.59]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 May 2021 09:06:04 -0700 Subject: Re: x86/fpu/xsave: protection key test failures To: Babu Moger , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, shuah@kernel.org, jroedel@suse.de, ubizjak@gmail.com, viro@zeniv.linux.org.uk, jpa@git.mail.kapsi.fi, fenghua.yu@intel.com, kan.liang@linux.intel.com, akpm@linux-foundation.org, rppt@kernel.org, Fan_Yang@sjtu.edu.cn, anshuman.khandual@arm.com, b.thiel@posteo.de, jgross@suse.com, keescook@chromium.org, seanjc@google.com, mh@glandium.org, sashal@kernel.org, krisman@collabora.com, chang.seok.bae@intel.com, 0x7f454c46@gmail.com, jhubbard@nvidia.com, sandipan@linux.ibm.com, ziy@nvidia.com, kirill.shutemov@linux.intel.com, suxingxing@loongson.cn, harish@linux.ibm.com, rong.a.chen@intel.com, linuxram@us.ibm.com, bauerman@linux.ibm.com, dave.kleikamp@oracle.com References: <7a407363-e074-aa84-3ca1-909b497122aa@intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------8E16EEEE763628152A53C51B" Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------8E16EEEE763628152A53C51B Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit On 5/26/21 8:25 AM, Babu Moger wrote: > On 5/25/21 7:20 PM, Dave Hansen wrote: >> On 5/25/21 5:03 PM, Babu Moger wrote: >>>> What values do PKRU and the shadow have when the test fails? Is PKRU 0? >>> It goes back to default value 0x55555554. The test is expecting it to be >>> 0. Printed them below. >>> >>> test_ptrace_of_child()::1346, pkey_reg: 0x0000000055555554 shadow: >>> 0000000000000000 >>> protection_keys_64: pkey-helpers.h:127: _read_pkey_reg: Assertion >>> `pkey_reg == shadow_pkey_reg' failed. >> That's backwards (shadow vs pkru) from what I was expecting. >> >> Can you turn on all the debuging? >> >> Just compile with -DDEBUG_LEVEL=5 > > Copied the logs at https://pastebin.com/gtQiHg8Q Well, it's a bit backwards from what I'm expecting. The PKRU=0 value *WAS* legitimate because all of the pkeys got allocated and their disable bits cleared. I think Andy was close when he was blaming: > static inline void write_pkru(u32 pkru) > { ... > pk = get_xsave_addr(¤t->thread.fpu.state.xsave, XFEATURE_PKRU); ... > if (pk) > pk->pkru = pkru; > __write_pkru(pkru); > } But that can't be it because PKRU ended up with 0x55555554. Something must have been writing 'init_pkru_value'. switch_fpu_finish() does that: > static inline void switch_fpu_finish(struct fpu *new_fpu) > { > u32 pkru_val = init_pkru_value; ... > if (current->mm) { > pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU); > if (pk) > pkru_val = pk->pkru; > } > __write_pkru(pkru_val); ... > } If 'new_fpu' had XSTATE_BV[PKRU]=0 then we'd have pk=NULL and 'pkru_val' would still have 'init_pkru_value'. *Then*, we'd have a shadow=0x0 and pkru=0x55555554. It would also only trigger if the hardware has an init tracker that fires when wrpkru(0). Intel doesn't do that. AMD must. Anyway, I need to think about this a bit more. But, an entirely guaranteed to be 100% untested patch is attached. I'm *NOT* confident this is the right fix. I don't have much AMD hardware laying around, so testing would be appreciated. --------------8E16EEEE763628152A53C51B Content-Type: text/x-patch; charset=UTF-8; name="pkrusig.patch" Content-Transfer-Encoding: quoted-printable Content-Disposition: attachment; filename="pkrusig.patch" diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/f= pu/internal.h index 8d33ad8..21402eb 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -582,6 +582,8 @@ static inline void switch_fpu_finish(struct fpu *new_= fpu) pk =3D get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU); if (pk) pkru_val =3D pk->pkru; + else + pkru_val =3D 0x0; } __write_pkru(pkru_val); =20 --------------8E16EEEE763628152A53C51B--