From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH] kvm: don't take vcpu mutex for obviously invalid vcpu ioctls Date: Tue, 23 Sep 2014 10:06:09 +0200 Message-ID: <542129F1.1080608@de.ibm.com> References: <1411167805-2458-1-git-send-email-dmatlack@google.com> <541FFEDE.9030800@redhat.com> <542027F6.4050205@de.ibm.com> <542032D4.305@redhat.com> <54207668.3030502@de.ibm.com> <5420788F.9050208@redhat.com> <20140923064918.GE30733@minantech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: David Matlack , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti To: Gleb Natapov , Paolo Bonzini Return-path: In-Reply-To: <20140923064918.GE30733@minantech.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 09/23/2014 08:49 AM, Gleb Natapov wrote: > On Mon, Sep 22, 2014 at 09:29:19PM +0200, Paolo Bonzini wrote: >> Il 22/09/2014 21:20, Christian Borntraeger ha scritto: >>> "while using trinity to fuzz KVM, we noticed long stalls on invalid ioctls. Lets bail out early on invalid ioctls". or similar? >> >> Okay. David, can you explain how you found it so that I can make up my >> mind? >> >> Gleb and Marcelo, a fourth and fifth opinion? :) >> > I agree with Christian that simpler fix is better here. > The overhead is minimal. If we ever notice this overhead > we can revert the patch all together since the problem it > fixes can only be inflicted on userspace by itself and there > are myriads other ways userspace can hurt itself. > Yes. Davids explanation also makes sense as a commit message. Paolo, if you use David patch with a better description of the "why" I am fine with this patch. Christian