From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xh8S40jKHzDqGG for ; Tue, 29 Aug 2017 10:20:52 +1000 (AEST) Date: Tue, 29 Aug 2017 10:13:19 +1000 From: Paul Mackerras To: Nicholas Piggin Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org Subject: Re: [PATCH v3 1/4] KVM: PPC: Book3S HV: POWER9 does not require secondary thread management Message-ID: <20170829001319.GE12629@fergus.ozlabs.ibm.com> References: <20170825043036.18236-1-npiggin@gmail.com> <20170825043036.18236-2-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170825043036.18236-2-npiggin@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Aug 25, 2017 at 02:30:33PM +1000, Nicholas Piggin wrote: > POWER9 CPUs have independent MMU contexts per thread, so KVM does not > need to quiesce secondary threads, so the hwthread_req/hwthread_state > protocol does not have to be used. So patch it away on POWER9, and patch > away the branch from the Linux idle wakeup to kvm_start_guest that is > never used. > > Add a warning and error out of kvmppc_grab_hwthread in case it is ever > called on POWER9. > > This avoids a hwsync in the idle wakeup path on POWER9. > > Signed-off-by: Nicholas Piggin Some of the feature sections seem a little unnecessary except for documentation purposes (e.g. the second one added after the kvm_no_guest label), but they won't actually hurt, so: Acked-by: Paul Mackerras