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Wed, 21 Apr 2021 18:36:06 +0000 Subject: Re: [PATCH 4/4] x86/speculation: Add PSF mitigation kernel parameters To: Bandan Das , Randy Dunlap Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, Jonathan Corbet References: <20210421090117.22315-1-rsaripal@amd.com> <20210421090117.22315-5-rsaripal@amd.com> <4c688fc7-67df-3187-54b2-bf20e510fb39@infradead.org> From: "Saripalli, RK" Message-ID: <28a97cec-964d-229b-fbd3-8c8c6ce71590@amd.com> Date: Wed, 21 Apr 2021 13:36:03 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [165.204.78.25] X-ClientProxiedBy: SA0PR11CA0080.namprd11.prod.outlook.com (2603:10b6:806:d2::25) To DM6PR12MB3435.namprd12.prod.outlook.com (2603:10b6:5:39::26) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [172.31.134.241] (165.204.78.25) by SA0PR11CA0080.namprd11.prod.outlook.com (2603:10b6:806:d2::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4042.18 via Frontend Transport; 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For now, the functionality will be just on and off. Later based on interest from community and other factors, I will online the prctl and seccomp variants of the mitigation. Thanks, RK On 4/21/2021 1:32 PM, Bandan Das wrote: > Randy Dunlap writes: > >> Hi, >> >> On 4/21/21 2:01 AM, Ramakrishna Saripalli wrote: >>> From: Ramakrishna Saripalli >>> >>> PSF mitigation introduces a new kernel parameter called >>> predict_store_fwd. >>> >>> Signed-off-by: Ramakrishna Saripalli >>> --- >>> Documentation/admin-guide/kernel-parameters.txt | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >>> index 04545725f187..58f6bd02385b 100644 >>> --- a/Documentation/admin-guide/kernel-parameters.txt >>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>> @@ -3940,6 +3940,11 @@ >>> Format: {"off"} >>> Disable Hardware Transactional Memory >>> >>> + predict_store_fwd [X86] This option controls PSF mitigation >>> + off - Turns on PSF mitigation. >>> + on - Turns off PSF mitigation. >>> + default : on. >> >> This should be formatted more like: >> >> + predict_store_fwd= [X86] This option controls PSF mitigation >> + off - Turns on PSF mitigation. >> + on - Turns off PSF mitigation. >> + default: on. >> >> But why does "off" turn it on and "on" turn it off? >> > Maybe, rename the parameter to something like psfd_disable, then off -> disables mitigation and on -> enables it. > Or just rewriting this to off -> turns off predictive store forwarding is probably ok too. > > Bandan > >> >>> + >>> preempt= [KNL] >>> Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC >>> none - Limited to cond_resched() calls >>> >> >> thanks. >