From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v2 03/10] KVM: arm/arm64: vgic-its: Improve error reporting on device table save Date: Sat, 14 Oct 2017 08:06:25 -0700 Message-ID: <20171014150625.GE5886@lvm> References: <1506518920-18571-1-git-send-email-eric.auger@redhat.com> <1506518920-18571-4-git-send-email-eric.auger@redhat.com> <20171013131618.GH8927@cbox> <0a5b2332-a88f-060f-6c0c-8c8d64f6a1f9@redhat.com> <20171013175653.GD17578@cbox> <29e61353-ac2d-b163-2a49-4215a1e596e0@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, marc.zyngier@arm.com, peter.maydell@linaro.org, andre.przywara@arm.com, wanghaibin.wang@huawei.com, wu.wubin@huawei.com To: Auger Eric Return-path: Content-Disposition: inline In-Reply-To: <29e61353-ac2d-b163-2a49-4215a1e596e0@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Sat, Oct 14, 2017 at 10:52:45AM +0200, Auger Eric wrote: > Hi Christoffer, > > On 13/10/2017 19:56, Christoffer Dall wrote: > > On Fri, Oct 13, 2017 at 04:22:25PM +0200, Auger Eric wrote: > >> Hi, > >> > >> On 13/10/2017 15:16, Christoffer Dall wrote: > >>> On Wed, Sep 27, 2017 at 03:28:33PM +0200, Eric Auger wrote: > >>>> At the moment the device table save() returns -EINVAL if > >>>> vgic_its_check_id() fails to return the gpa of the entry > >>>> associated to the device/collection id. Let vgic_its_check_id() > >>>> return an int instead of a bool and return a more precised > >>>> error value: > >>>> - EINVAL in case the id is out of range > >>>> - EFAULT if the gpa is not provisionned or is not valid > >>>> > >>> > >>> This is just to ease debugging, yes? > >> > >> I understood user-space should be able to discriminate between bad guest > >> programming and values corrupted by the userspace (regs for instance). > >> In first case QEMU should not abort. In latter case it should abort. > > > > So what is userspace supposed to do in the first case? > > I was referring to https://www.spinics.net/lists/kvm/msg148791.html. > QEMU is supposed to write a message in that case but not cause an abort(). > > This is what is actually implemented on QEMU side. In case the ioctl > returns -EFAULT, we don't abort but simply warn. However at the moment > we return -EINVAL in some circumstances where - I think - we should > return -EFAULT. Hence this patch attempting to be more precise on the > cause of the failure instead of abruptly returning -EINVAL here. > ok, thanks makes sense. Thanks for sharing the background. -Christoffer