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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 6 May 2019 02:33:13 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x461XCuR48038012 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 6 May 2019 01:33:12 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 79DFFAE045; Mon, 6 May 2019 01:33:12 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2B029AE04D; Mon, 6 May 2019 01:33:12 +0000 (GMT) Received: from ozlabs.au.ibm.com (unknown [9.192.253.14]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 6 May 2019 01:33:12 +0000 (GMT) Received: from [10.61.2.125] (haven.au.ibm.com [9.192.254.114]) (using TLSv1.2 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id 4377AA0125; Mon, 6 May 2019 11:33:10 +1000 (AEST) Subject: Re: [PATCH] powerpc/64s: support nospectre_v2 cmdline option To: "Christopher M. Riedl" , linuxppc-dev@ozlabs.org References: <20190505221048.28212-1-cmr@informatik.wtf> From: Andrew Donnellan Date: Mon, 6 May 2019 11:32:58 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190505221048.28212-1-cmr@informatik.wtf> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-AU Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19050601-0028-0000-0000-0000036AA67E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19050601-0029-0000-0000-0000242A197F Message-Id: <271ab704-e3d2-f04c-4758-2b08c1b3909c@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-05-06_01:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905060011 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 6/5/19 8:10 am, Christopher M. Riedl wrote: > Add support for disabling the kernel implemented spectre v2 mitigation > (count cache flush on context switch) via the nospectre_v2 cmdline > option. > > Suggested-by: Michael Ellerman > Signed-off-by: Christopher M. Riedl > --- > > arch/powerpc/kernel/security.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c > index b33bafb8fcea..f7c34745cd0f 100644 > --- a/arch/powerpc/kernel/security.c > +++ b/arch/powerpc/kernel/security.c > @@ -28,7 +28,7 @@ static enum count_cache_flush_type count_cache_flush_type = COUNT_CACHE_FLUSH_NO > bool barrier_nospec_enabled; > static bool no_nospec; > static bool btb_flush_enabled; > -#ifdef CONFIG_PPC_FSL_BOOK3E > +#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64) > static bool no_spectrev2; > #endif > > @@ -106,7 +106,7 @@ static __init int barrier_nospec_debugfs_init(void) > device_initcall(barrier_nospec_debugfs_init); > #endif /* CONFIG_DEBUG_FS */ > > -#ifdef CONFIG_PPC_FSL_BOOK3E > +#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64) > static int __init handle_nospectre_v2(char *p) > { > no_spectrev2 = true; > @@ -114,6 +114,9 @@ static int __init handle_nospectre_v2(char *p) > return 0; > } > early_param("nospectre_v2", handle_nospectre_v2); > +#endif /* CONFIG_PPC_FSL_BOOK3E || CONFIG_PPC_BOOK3S_64 */ > + > +#ifdef CONFIG_PPC_FSL_BOOK3E > void setup_spectre_v2(void) > { > if (no_spectrev2) > @@ -391,6 +394,13 @@ static void toggle_count_cache_flush(bool enable) > > void setup_count_cache_flush(void) > { > + if (no_spectrev2) { > + if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) > + || security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED)) > + pr_warn("Spectre v2 mitigations not under software control, can't disable\n"); If one of those ftrs is set, what's the impact of not calling toggle_count_cache_flush()? > + return; > + } > + > toggle_count_cache_flush(true); > } > > -- Andrew Donnellan OzLabs, ADL Canberra ajd@linux.ibm.com IBM Australia Limited