Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754362Ab3JBV6z (ORCPT ); Wed, 2 Oct 2013 17:58:55 -0400 Received: from e23smtp07.au.ibm.com ([202.81.31.140]:39808 "EHLO e23smtp07.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753834Ab3JBV6x (ORCPT ); Wed, 2 Oct 2013 17:58:53 -0400 Message-ID: <1380751112.645.64.camel@pasglop> Subject: Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems From: Benjamin Herrenschmidt To: Alexander Graf Cc: Paolo Bonzini , Paul Mackerras , Gleb Natapov , Michael Ellerman , linux-kernel@vger.kernel.org, mpm@selenic.com, herbert@gondor.hengli.com.au, linuxppc-dev@ozlabs.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, tytso@mit.edu Date: Thu, 03 Oct 2013 07:58:32 +1000 In-Reply-To: <668E4650-BC22-4CBF-A282-E7875DF29DB6@suse.de> References: <1380177066-3835-1-git-send-email-michael@ellerman.id.au> <1380177066-3835-3-git-send-email-michael@ellerman.id.au> <5243F933.7000907@redhat.com> <20131001083426.GB27484@concordia> <20131001083908.GA17294@redhat.com> <1380620338.645.22.camel@pasglop> <524AAFAA.3010801@redhat.com> <20131002050940.GA25363@drongo> <524BDD73.3020106@redhat.com> <1380704789.645.57.camel@pasglop> <668E4650-BC22-4CBF-A282-E7875DF29DB6@suse.de> Organization: IBM Australia Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100221-0260-0000-0000-000003B892B1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 789 Lines: 22 On Wed, 2013-10-02 at 11:11 +0200, Alexander Graf wrote: > Right, and the difference for the patch in question is really whether > we handle in in kernel virtual mode or in QEMU, so the bulk of the > overhead (kicking threads out of guest context, switching MMU > context, etc) happens either way. > > So the additional overhead when handling it in QEMU here really boils > down to the user space roundtrip (plus another random number read > roundtrip). Hrm, Michael had a real mode version ... not sure where it went then. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/