From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227IKfpYP5Dbi+XWFSgHewoQ61i3Gx320JxJX95hJGnBDh6JxB1H7RihNw/0OfzbzCR5MFTe ARC-Seal: i=1; a=rsa-sha256; t=1516893207; cv=none; d=google.com; s=arc-20160816; b=gc/eBDfqPfBu3W9AoTwgz7q5BxV9b2iWNRrk+HnpMk1058egIoc1TrGH35EMlKmEQX faYbD6kiW6pa30qugsiH21YjxZKf2/seFW+8qHIMSO1aL+FZBnwH9JFYlCKFaMTdhBRY 2yPhbS2c+XM5yMl1xFHMuLcQ6F/DfJEwlYGUmYeKS2QycjW719mNm3OQQVdnQK1kemCC g/E7tXu44XEP+IElVoQ3BYxQz6+GKk9nCDJxOY5OXsZQET6YRWoqfxw1yE6AM//GN8wR VPZYEigYaZGSJfnGqKs921JJV+MS0PnU+Z4PLaqoB9npLHRozUbJ5pOy9UMO0MDTKm/3 6AIQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:date :arc-authentication-results; bh=dQ40amR4WdQVDaJJ2Nv/7cKpl11cqT5tbTuH8LI7sKo=; b=gwg8zZvzUANIOU/KS+lLxCUrDGCa80v2fqMUGjBzkBeb2Sku0U5s/bECgLJadKunyE Qt7zDGpbecXeZIcaECl6qR83ht3eME3IAqtzzCknjdXQIurhR4J671+ZFZO8p32MsO5H kS70nDSOtDvGCIWi4KsVx2qQLq37fZPVP/cKqlqTHOVGOuiw9h0geh71U0x66V/oG1TB fznsEUF/Pn3nKzYOMgsja4RWdOeSF39qCUSwwl7AyVB9jWGTsPTtby0AmITJjtN3Amh/ 7t7I8Skb5sgfqS7Q9QypAEfXyWUcF8mPMuQumFxg1vHa4Awzq1dnM9/3Ii8GdbcajRC3 8TVA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of gnomes@lxorguk.ukuu.org.uk designates 82.70.14.225 as permitted sender) smtp.mailfrom=gnomes@lxorguk.ukuu.org.uk Authentication-Results: mx.google.com; spf=pass (google.com: domain of gnomes@lxorguk.ukuu.org.uk designates 82.70.14.225 as permitted sender) smtp.mailfrom=gnomes@lxorguk.ukuu.org.uk Date: Thu, 25 Jan 2018 15:12:52 +0000 From: Alan Cox To: David Woodhouse Cc: 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, dave.hansen@intel.com, ashok.raj@intel.com, mingo@kernel.org Subject: Re: [PATCH v4 5/7] x86/pti: Do not enable PTI on processors which are not vulnerable to Meltdown Message-ID: <20180125151252.735a75ac@alans-desktop> In-Reply-To: <1516872189-16577-6-git-send-email-dwmw@amazon.co.uk> References: <1516872189-16577-1-git-send-email-dwmw@amazon.co.uk> <1516872189-16577-6-git-send-email-dwmw@amazon.co.uk> Organization: Intel Corporation X-Mailer: Claws Mail 3.15.1-dirty (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590555846213033818?= X-GMAIL-MSGID: =?utf-8?q?1590577812127497218?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Thu, 25 Jan 2018 09:23:07 +0000 David Woodhouse wrote: > Also, for CPUs which don't speculate at all, don't report that they're vulnerable > to the Spectre variants either. > > Leave the cpu_no_meltdown[] match table with just X86_VENDOR_AMD in it for now, > even though that could be done with a simple comparison, on the assumption that > we'll have more to add. > > Based on suggestions from Dave Hansen and Alan Cox. Looks good to me. I've been doing some more document spelunking and have some more stuff for 32bit but not for 64bit capable systems. X86_VENDOR_NSC, 5 is safe as the MediaGX/Geode doesn't have speculation. However CYRIX,5 isn't because there are a mix of CPU types there. Most interesting is the Cyrix one. I'm going to have to resurrect my Cyrix kit because some of the Cyrix processors actually have control bits to turn on/off the BTB and also the return stack predictor (PCR0 bits 1 and 0 respecively) and no lfence so you need to change system flags or reload a segment register to force a stall. Alan