From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH 0/5] KVM: arm/arm64: fix some races and allow userspace to set MPIDR Date: Wed, 8 Mar 2017 09:27:12 -0800 Message-ID: <20170308172712.GE109908@lvm> References: <20170227175504.15751-1-drjones@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 94838408EB for ; Wed, 8 Mar 2017 12:25:55 -0500 (EST) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id njdh2UZ+qiSk for ; Wed, 8 Mar 2017 12:25:52 -0500 (EST) Received: from mail-wr0-f181.google.com (mail-wr0-f181.google.com [209.85.128.181]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id CBDC5405DA for ; Wed, 8 Mar 2017 12:25:51 -0500 (EST) Received: by mail-wr0-f181.google.com with SMTP id u108so28220340wrb.3 for ; Wed, 08 Mar 2017 09:27:15 -0800 (PST) Content-Disposition: inline In-Reply-To: <20170227175504.15751-1-drjones@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Andrew Jones Cc: marc.zyngier@arm.com, ashoks@broadcom.com, imammedo@redhat.com, kvmarm@lists.cs.columbia.edu List-Id: kvmarm@lists.cs.columbia.edu Hi Drew, On Mon, Feb 27, 2017 at 06:54:59PM +0100, Andrew Jones wrote: > This series fixes four races. Two are easy to produce with a > kvm-unit-test test[1], but the other two would be quite hard. I > didn't even try to produce those. The two hard to produce races are > addressed by changing vcpu->arch.pause and vcpu->arch.power_off to > vcpu requests. The two easy to produce races are addressed in two > different ways: the first takes advantage of power_off having been > changed to a vcpu request, the second caches vcpu MPIDRs in order > to avoid extracting them from sys_regs. When introducing the MPIDR > cache we also introduce a new feature (userspace settable MPIDRs). > > Support for userspace settable MPIDRs was already posted once[2], > but rejected due to not having a use case. We have one now, which > is to satisfy QEMU's need for the MPDIR information very early, > before vcpu-init has even run. While the original posting author > wasn't me, I've taken authorship now, as I've changed the patch > substantially. If anybody disagrees with that, then feel free to > suggest alternatives. The QEMU counterpart has been posted[3]. > > This series is based on Radim's recent posting[4] that improves > the vcpu-request framework. I've tested the series on a couple > AArch64 platforms and compile-tested the arm bits. So as we discussed during lunch today, it would be awesome if you could split this up into a series that fixes the identified races and a separate series for the introduction of supporting setting the MPIDR from user space. Thanks a lot! -Christoffer