From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] kvm: don't take vcpu mutex for obviously invalid vcpu ioctls Date: Tue, 23 Sep 2014 09:49:18 +0300 Message-ID: <20140923064918.GE30733@minantech.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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christian Borntraeger , David Matlack , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti To: Paolo Bonzini Return-path: Content-Disposition: inline In-Reply-To: <5420788F.9050208@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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. -- Gleb.