From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x226vZrPU6N+54gdxtKsQI+fYffm2e4iH3kLeCGjfwFlnQTtWLMOE9rupjtpVLY1s1kKCzeHF ARC-Seal: i=1; a=rsa-sha256; t=1517275928; cv=none; d=google.com; s=arc-20160816; b=ha0ml9+TLYo3L5XmoMm3R/568Pv8Nw9Fe0NQReC2yQQnPZgmqOo6BYNrebkA0gcR5s KBaqgEBJaoJEXD59Smt/Quw6qzvCli7Phaa9E4iem7Gn3+3Jm7CPZaBmsoe42EoYHZAv tXMEiLmPFTb1htXz8ppe8admV7CIXXOCD4qPKBDZ2nZWR6P5B4bTcQRVH1Ie+iqKmWjs Mtoi7NF98JtWLxkAjQz+V2p0XbDly+R7Dx56Xja6WPklpY/18dYHkEmD7eHhUEGzxnQl hz/ImRmX/SRvLDjBLQPp17q2huzqU08dlUarWNJOwv2jLSajfe3xQVIULqXo/hxQARlr 2aYw== 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:cc:to:subject :arc-authentication-results; bh=inwzYWD15TxLhjIlvQ4ABb+GBdc7DYdXC/ZCKOy3Azk=; b=DjKj4w9E3pxwKEZimen0HZ9KwN+pjO4wUrS0kqQ+txcpsthpfp2N8aJ283oTB4Hfby o9vFM598q/P5kzhD0O67fVWaGJesFONzWNFVsa6pJnk62ReJJ0igiDeih+d7OkOpUg9P aNzWK3e5tvm5enpuop9aJzlP8DKSZ1Oig5OTImA3/kwQEtxQZ98xN4YTtrlKmdS6ZMxD vmk876I5IuT87+v2TYRXxsDtnjR+Y/AyFbOHf8OZ6N2b2BgSZEgWVN8iUNP2A+vQOLhk XQcJVCTqI2cYAaoDuZPXD2N9WamdZNLlRPpRA2mWuCTj4/nGaMFJ4ukeBS4OdMlbUs3j 17Fg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of arjan@linux.intel.com designates 134.134.136.65 as permitted sender) smtp.mailfrom=arjan@linux.intel.com Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of arjan@linux.intel.com designates 134.134.136.65 as permitted sender) smtp.mailfrom=arjan@linux.intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,433,1511856000"; d="scan'208";a="30480052" Subject: Re: [RFC,05/10] x86/speculation: Add basic IBRS support infrastructure To: Linus Torvalds , David Woodhouse Cc: Eduardo Habkost , KarimAllah Ahmed , Linux Kernel Mailing List , Andi Kleen , Andrea Arcangeli , Andy Lutomirski , Ashok Raj , Asit Mallick , Borislav Petkov , Dan Williams , Dave Hansen , Greg Kroah-Hartman , "H . Peter Anvin" , Ingo Molnar , Janakarajan Natarajan , Joerg Roedel , Jun Nakajima , Laura Abbott , Masami Hiramatsu , Paolo Bonzini , Peter Zijlstra , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Thomas Gleixner , Tim Chen , Tom Lendacky , KVM list , the arch/x86 maintainers , "Dr. David Alan Gilbert" References: <1516476182-5153-6-git-send-email-karahmed@amazon.de> <20180129201404.GA1588@localhost.localdomain> <1517257022.18619.30.camel@infradead.org> <20180129204256.GV25150@localhost.localdomain> <31415b7f-9c76-c102-86cd-6bf4e23e3aee@linux.intel.com> <1517259759.18619.38.camel@infradead.org> From: Arjan van de Ven Message-ID: <6c024f95-b12c-9c66-91d7-208ed2c380ff@linux.intel.com> Date: Mon, 29 Jan 2018 17:32:05 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590140581449802182?= X-GMAIL-MSGID: =?utf-8?q?1590979123577997323?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 1/29/2018 4:23 PM, Linus Torvalds wrote: > > Why do you even _care_ about the guest, and how it acts wrt Skylake? > What you should care about is not so much the guests (which do their > own thing) but protect guests from each other, no? the most simple solution is that we set the internal feature bit in Linux to turn on the "stuff the RSB" workaround is we're on a SKL *or* as a guest in a VM. The stuffing is not free, but it's also not insane either... so if it's turned on in guests, the impact is still limited, while bare metal doesn't need it at all