From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH v3 01/16] KVM: Take vcpu->mutex outside vcpu_load Date: Tue, 5 Dec 2017 15:32:30 +0100 Message-ID: <241fe130-bc3f-533e-4bef-604b04b9818d@de.ibm.com> References: <20171204203538.8370-1-cdall@kernel.org> <20171204203538.8370-2-cdall@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20171204203538.8370-2-cdall@kernel.org> Content-Language: en-US Sender: kvm-owner@vger.kernel.org To: Christoffer Dall , kvm@vger.kernel.org Cc: Andrew Jones , Christoffer Dall , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Marc Zyngier , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, James Hogan , linux-mips@linux-mips.org, Paul Mackerras , kvm-ppc@vger.kernel.org, Cornelia Huck , linux-s390@vger.kernel.org List-Id: kvmarm@lists.cs.columbia.edu On 12/04/2017 09:35 PM, Christoffer Dall wrote: > From: Christoffer Dall > > As we're about to call vcpu_load() from architecture-specific > implementations of the KVM vcpu ioctls, but yet we access data > structures protected by the vcpu->mutex in the generic code, factor > this logic out from vcpu_load(). > > x86 is the only architecture which calls vcpu_load() outside of the main > vcpu ioctl function, and these calls will no longer take the vcpu mutex > following this patch. However, with the exception of > kvm_arch_vcpu_postcreate (see below), the callers are either in the > creation or destruction path of the VCPU, which means there cannot be > any concurrent access to the data structure, because the file descriptor > is not yet accessible, or is already gone. > > kvm_arch_vcpu_postcreate makes the newly created vcpu potentially > accessible by other in-kernel threads through the kvm->vcpus array, and > we therefore take the vcpu mutex in this case directly. > > Signed-off-by: Christoffer Dall Looks good to me.