From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227tw82x8tXNdm83WszEfXvT74w2+EXDQThl5R9HmscvOmiNJ7ANpQSo940zR/IlnkjQPbi6 ARC-Seal: i=1; a=rsa-sha256; t=1516757316; cv=none; d=google.com; s=arc-20160816; b=vujHGcbdSjqfo0rX9/BpjomaewziRbNsQCQScydXmy0iEeHGLEJmr6HaoJJRna3ZoG A/dh58uYj6cviGH8IkcvDXM9wCTaWTZqP8kEIPVtpxTY+XIQyaEMg1l/xlPv2PdCi/Pr CfxgeKRrb/bmaWVWyGKsrKPgtvROsI7BZvkCkXr0bwmMb8+SRQRLSh1Y76qEbZjuoHue MvUsYsx7GkyaBqUUztTx3NAu2SW8v2Z8BcKRHL/G4ZK2sEXxn3nj/2kGzQvQsqnJIpl7 wHn+FX/59Gpjr1jmyNVBO4PqDoSN9aMuez0TSGzAiOVzaDtVZf+IX9EB2ez3wKadfYy8 qySw== 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=qXN78aK91T5XVROquIRPC2+w5KmPgs3xZ0q8IvOkYOU=; b=gRJCWTORQj3G1rdWsCRS5eWiFVBiLLtMJOMFvkKxOINYdTolEE5S8KKVViqtCeWyg+ VNw6Dw6oaX0v8UVWZoSk+B/9honuskwT6IzXJJ0KhgyaazhIEmCFGlU3MtoIyDcGSfzl iLXxR6jQn1YLbnluLu6T3MRWRzU0AYXoCGXsDBhEo0HvWhXc/CeMr/vbgJY+2RR6Us36 5J2kxIFgTzaREJwKIkrd/OftQqm7MqPYODbe2zYCmI7t/kb8d/xeDTd6tdWAWbcRd/20 QDlugcQmTKU1tgKngW0tRJLs0UdvKatjxpOpciy2omgwHeDyY/+Qu3foSNZnvCcvSDDt hSyA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.31 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 134.134.136.31 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="5.46,404,1511856000"; d="scan'208";a="12559325" Subject: Re: [PATCH v2 2/5] x86/cpufeatures: Add Intel feature bits for Speculation Control To: "Woodhouse, David" , "linux-kernel@vger.kernel.org" , "tim.c.chen@linux.intel.com" , "arjan@linux.intel.com" , "Raslan, KarimAllah" , "peterz@infradead.org" , "torvalds@linux-foundation.org" , "tglx@linutronix.de" , "ak@linux.intel.com" , "x86@kernel.org" , "pbonzini@redhat.com" , "bp@alien8.de" , "thomas.lendacky@amd.com" , "gregkh@linux-foundation.org" References: <1516726375-25168-1-git-send-email-dwmw@amazon.co.uk> <1516726375-25168-3-git-send-email-dwmw@amazon.co.uk> <3ebee57a-b116-68f6-0421-0640f5e552f5@intel.com> <1516757037.13558.65.camel@amazon.co.uk> From: Dave Hansen Message-ID: Date: Tue, 23 Jan 2018 17:28:35 -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: <1516757037.13558.65.camel@amazon.co.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590402900695283949?= X-GMAIL-MSGID: =?utf-8?q?1590435320512292378?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 01/23/2018 05:23 PM, Woodhouse, David wrote: > On Tue, 2018-01-23 at 10:43 -0800, Dave Hansen wrote: ... >>>   /* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */ >>>   #define X86_FEATURE_AVX512_4VNNIW    (18*32+ 2) /* AVX-512 Neural Network Instructions */ >>>   #define X86_FEATURE_AVX512_4FMAPS    (18*32+ 3) /* AVX-512 Multiply Accumulation Single precision */ >>> +#define X86_FEATURE_SPEC_CTRL                (18*32+26) /* Speculation Control (IBRS + IBPB) */ >>> +#define X86_FEATURE_STIBP            (18*32+27) /* Single Thread Indirect Branch Predictors */ >>> +#define X86_FEATURE_ARCH_CAPABILITIES        (18*32+29) /* IA32_ARCH_CAPABILITIES MSR (Intel) */ >> Should we be adding flags (STIBP) for which we currently have no user in >> the kernel? > They're in an existing word (now) so it costs us absolutely nothing to > do so. And they'll be exposed to KVM guests in imminent patches if > nothing else. Doesn't just defining it here generate something in the tables that then get exported in /proc/cpuinfo? That's far from our most strict ABI, but a single #define here can be seen by users IIRC.