From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59066) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eYnxY-0002q9-Cx for qemu-devel@nongnu.org; Tue, 09 Jan 2018 02:04:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eYnxU-0000qF-Df for qemu-devel@nongnu.org; Tue, 09 Jan 2018 02:04:32 -0500 Received: from bart.luffy.cx ([78.47.78.131]:51073) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eYnxU-0000pJ-6H for qemu-devel@nongnu.org; Tue, 09 Jan 2018 02:04:28 -0500 From: Vincent Bernat References: <20180108205052.24385-1-vincent@bernat.im> <20180108211623.GJ6646@localhost.localdomain> <242287261.31733448.1515451036017.JavaMail.zimbra@redhat.com> <20180108225625.GP6646@localhost.localdomain> <848013447.31735187.1515452970885.JavaMail.zimbra@redhat.com> <20180108231917.GQ6646@localhost.localdomain> Date: Tue, 09 Jan 2018 08:04:26 +0100 In-Reply-To: <20180108231917.GQ6646@localhost.localdomain> (Eduardo Habkost's message of "Mon, 8 Jan 2018 21:19:17 -0200") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] target-i386: add pcid to both Sandy Bridge and Ivy Bridge List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: Paolo Bonzini , Richard Henderson , qemu-devel@nongnu.org =E2=9D=A6 8 janvier 2018 21:19 -0200, Eduardo Habkost =C2=A0: >> > GET_SUPPORTED_CPUID seems to still return PCID as supported >> > without EPT, doesn't it? >>=20 >> Indeed it is! It will also be useful for KPTI performance without >> INVPCID, but it won't be useful without EPT. > > Well, I can live with "not useful without EPT", as long as it > doesn't mean "broken without EPT". It looks like we can safely > enable it, as long as: > > 2) we confirm if all Intel Westmere/SandyBridge/IvyBridge CPUs > have PCID; I didn't find an authoritative information about that on Intel website. Various sites indeed says the feature was introduced in Westmere. And Greg KH mentions Westmere here too: https://mail-archive.com/linux-kernel@vger.kernel.org/msg1576774.html > 1) QEMU documentation states that it requires Linux v3.6 or newer > for KVM. I have updated the patch and sent it in a new thread. It's now based on x86-next. --=20 Clothes make the man. Naked people have little or no influence on society. -- Mark Twain