From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x225kTovkQ1KxrV9Ac+GhKR8No99JqzC6fUNb+qSgRzUTkjDaUFOjykSOqkThyfFtYxeKIIF2 ARC-Seal: i=1; a=rsa-sha256; t=1516903854; cv=none; d=google.com; s=arc-20160816; b=u10pavhH+QAhiH4Wg4EujqxGS70xWUfNChKZSpjAgl+M6rDWZLroiHiNdz8FqbBXG0 jQ5pmpEhtucZaNdBLWYV70wt3gPKMC2gBS/A8Z63g+KceE0VuoebB0YN8FO/J+lEN+63 jJz2QyiVOrmhu/98D1SkdZpPuORB3WAxyFpui8qIs/WP5sfeWqLc+1usc2eVto2DXQ56 sEg+zELfj25aTGHspcP38m8cACOyC3DSjjgBwnMrX8S1nzs+A4Rbw3nJsEpelOfuORFV FtW6jvaiiTEwFgbsK7IM8CB6dwo1hNpueVgcSTwytsIJ+nkpUDn1t+7jE+YQ26zAjNRv icLQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:to:subject :arc-authentication-results; bh=0/peYR+rGdUSbIYFUi+eapBLYIfgpWokNSfXHHzV3cE=; b=zm2vpb5ZPA3t2FGcMdWl53BZ4qkFdUjyL7fl3oWurwZQ2n2k+3SmFcw80n8/tqSr46 +tu93XVW8yM6Tk07eTPfKs7pC5Z9lZXUESOCMIYfHISiV1ZlhIpKrAzyFipgyoGmlPlk eBp6mDc+zLSvTImY0Rv+O3xRtSNQsYwppzTyuC47vFe7tli7Je/dJbeQbptt2DLn0/Ro qJbok8CzTQm28ueQ/YmRAL81iejnLfMarRBog4BeNZnhkOzb6DUIj7+pqtOgp7AytPm8 9R7KrVKAKdAJuMvZcrrNJ7g8xKE9VzXoICjPxIkye4VP/HYFyAWTjXKyKXCJ/fcU058R z2Gg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.65 as permitted sender) smtp.mailfrom=dave.hansen@intel.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.65 as permitted sender) smtp.mailfrom=dave.hansen@intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,412,1511856000"; d="scan'208";a="26342185" Subject: Re: [PATCH v5 5/7] x86/pti: Do not enable PTI on processors which are not vulnerable to Meltdown To: David Woodhouse , arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de, x86@kernel.org, linux-kernel@vger.kernel.org, tim.c.chen@linux.intel.com, bp@alien8.de, peterz@infradead.org, pbonzini@redhat.com, ak@linux.intel.com, torvalds@linux-foundation.org, gregkh@linux-foundation.org, gnomes@lxorguk.ukuu.org.uk, ashok.raj@intel.com, mingo@kernel.org References: <1516896855-7642-1-git-send-email-dwmw@amazon.co.uk> <1516896855-7642-6-git-send-email-dwmw@amazon.co.uk> From: Dave Hansen Message-ID: Date: Thu, 25 Jan 2018 10:10:52 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <1516896855-7642-6-git-send-email-dwmw@amazon.co.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590581674274638091?= X-GMAIL-MSGID: =?utf-8?q?1590588975851952619?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 01/25/2018 08:14 AM, David Woodhouse wrote: > +static bool __init early_cpu_vulnerable_meltdown(struct cpuinfo_x86 *c) > +{ > + u64 ia32_cap = 0; > + > + if (x86_match_cpu(cpu_no_meltdown)) > + return false; > + > + if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES)) > + rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap); > + > + /* Rogue Data Cache Load? No! */ > + if (ia32_cap & ARCH_CAP_RDCL_NO) > + return false; > + > + return true; > +} Feel free to add my ack on this. It looks fine to me. I'll test and submit any necessary fixes once I actually get a system that has this bit.