From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2934828-1520038463-2-4387438510545683400 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, RCVD_IN_DNSWL_NONE -0.0001, RCVD_IN_MSPIKE_H2 -0.001, SPF_PASS -0.001, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.85.192.194', Host='mail-pf0-f194.google.com', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='utf-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: alex.shi@linaro.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520038462; b=UQY3YuiXub5dRPkOmz5MCBWSJ45gg68j9MePSmN4ikEEPmb 3fPlhDzUhrp6FnIr/2VXciB1EXCupPS3stYg2yRgnj1/uwaMeYjvt3HR6/qdUJo1 GonVxRL76MBwEGbpfVqoAEo3iBouGXBVYL1bsaGix535MoOq42lTxbG+dpgtGKt/ uaKXNcBpgr8OUaBRm10H2PFB1YDxNJsYwBNKoWZfZUUWdhExfgIckjUFHgVLz6W8 CAzC190w+jfjiiZuZ8GVYhjeL6ABJSnL+RoJFPF+5i7X6F07AuuFWDi566i9nnKe Fw62CCeSbPIcDowMwY3GszET+xwSbirgGmHMotw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=subject:to:cc:references:from:message-id :date:mime-version:in-reply-to:content-type :content-transfer-encoding; s=arctest; t=1520038462; bh=7oFJ1hLM XeLEH4Mumm8V3lGsMwYIl5SiaBNQjpqfxOA=; b=g8+EJydedGte/wZMN42w9Qsc d32iukzP9DmqidOQShfmngICkYLrGO2Zs8rwc+DPAMHQsh9mNAOUONfNCKaS7x0u 62FIGVEDTx9JqLXXWfQhUim4z17QapXvZl3ooLBWyRH0FrbcOuPwpq9IXyHAIpsl AEEp9qX5s9hOtuKUDI9p21bpuF6tJHDxssvMujuVMdF8QZhUdqP72+jqNS+fXsL5 qqieQ9rcinBjhuLKOM6yjJyODTT0HXNnPpaof2AATUe2N0yHN4ddG2H42ICmG6hg Cw4pDXrR3zNylKr+XevedhWm55doeeKPbm6UxzWtwBadrgZ+NT5UO/WuqME+VQ== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=pass (1024-bit rsa key sha256) header.d=linaro.org header.i=@linaro.org header.b=IZUBn5f7 x-bits=1024 x-keytype=rsa x-algorithm=sha256 x-selector=google; dmarc=pass (p=none,d=none) header.from=linaro.org; iprev=pass policy.iprev=209.85.192.194 (mail-pf0-f194.google.com); spf=pass smtp.mailfrom=alex.shi@linaro.org smtp.helo=mail-pf0-f194.google.com; x-aligned-from=pass; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=JvqpA9ms; x-ptr=pass x-ptr-helo=mail-pf0-f194.google.com x-ptr-lookup=mail-pf0-f194.google.com; x-return-mx=pass smtp.domain=linaro.org smtp.result=pass smtp_is_org_domain=yes header.domain=linaro.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=pass (1024-bit rsa key sha256) header.d=linaro.org header.i=@linaro.org header.b=IZUBn5f7 x-bits=1024 x-keytype=rsa x-algorithm=sha256 x-selector=google; dmarc=pass (p=none,d=none) header.from=linaro.org; iprev=pass policy.iprev=209.85.192.194 (mail-pf0-f194.google.com); spf=pass smtp.mailfrom=alex.shi@linaro.org smtp.helo=mail-pf0-f194.google.com; x-aligned-from=pass; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=JvqpA9ms; x-ptr=pass x-ptr-helo=mail-pf0-f194.google.com x-ptr-lookup=mail-pf0-f194.google.com; x-return-mx=pass smtp.domain=linaro.org smtp.result=pass smtp_is_org_domain=yes header.domain=linaro.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Google-Smtp-Source: AG47ELsHVrSwfJaRJ1Uo0uIdGMsgh4YdXof+WnymJVDZdWd0LROFFoPsWlOMNcu6QuZlLzXEJobMkg== Subject: Re: [PATCH 00/45] arm Spectre fix backport review for LTS 4.9 To: Will Deacon Cc: Greg KH , Marc Zyngier , Ard Biesheuvel , Catalin Marinas , stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <1519908862-11425-1-git-send-email-alex.shi@linaro.org> <20180301164630.GB23321@kroah.com> <20180302103046.GC19323@arm.com> From: Alex Shi Message-ID: Date: Sat, 3 Mar 2018 08:54:10 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180302103046.GC19323@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 03/02/2018 06:30 PM, Will Deacon wrote: > On Fri, Mar 02, 2018 at 05:02:32PM +0800, Alex Shi wrote: >> As testing the spectre bug fix, that's a good question. I also asked >> this question to original patch authors, like Marc. They said they just >> figure out these patches could block spectre or meltdown issue. From my >> side, I just reproduced the process internal spectre. But all fix on arm >> can not resolve the user space internal spectre. It can block from user >> to kernel or kernel to user spectre according the code purose. So I >> believe these patch could do their job. And arm cpu would drop the >> spectre branches if it has 20+ 'nop' instructions... > > Since this is archived on a public list and I don't want people to rely on > this, no, you cannot rely on "20+ 'nop' instructions" to work around > spectre on arm/arm64. It might prevent a particular PoC working on a > particular SoC, but it's fragile at best. > Thanks for comments, Will! Yes, I full understand the difference between SoCs. Thanks for point it out! Regards Alex