From mboxrd@z Thu Jan 1 00:00:00 1970 From: Halil Pasic Subject: Re: [PATCH v3 7/8] virtio/s390: use DMA memory for ccw I/O and classic notifiers Date: Tue, 4 Jun 2019 15:08:19 +0200 Message-ID: <20190604150819.1f8707b5.pasic@linux.ibm.com> References: <20190529122657.166148-1-mimu@linux.ibm.com> <20190529122657.166148-8-mimu@linux.ibm.com> <20190603181716.325101d9.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190603181716.325101d9.cohuck@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Cornelia Huck Cc: Vasily Gorbik , Linux-S390 Mailing List , Thomas Huth , Claudio Imbrenda , KVM Mailing List , Sebastian Ott , "Michael S . Tsirkin" , Pierre Morel , Farhan Ali , Heiko Carstens , Eric Farman , virtualization@lists.linux-foundation.org, Christoph Hellwig , Christian Borntraeger , Michael Mueller , Viktor Mihajlovski , Janosch Frank List-Id: virtualization@lists.linuxfoundation.org On Mon, 3 Jun 2019 18:17:16 +0200 Cornelia Huck wrote: > On Wed, 29 May 2019 14:26:56 +0200 > Michael Mueller wrote: > > > From: Halil Pasic > > > > Before virtio-ccw could get away with not using DMA API for the pieces of > > memory it does ccw I/O with. With protected virtualization this has to > > change, since the hypervisor needs to read and sometimes also write these > > pieces of memory. > > > > The hypervisor is supposed to poke the classic notifiers, if these are > > used, out of band with regards to ccw I/O. So these need to be allocated > > as DMA memory (which is shared memory for protected virtualization > > guests). > > > > Let us factor out everything from struct virtio_ccw_device that needs to > > be DMA memory in a satellite that is allocated as such. > > > > Note: The control blocks of I/O instructions do not need to be shared. > > These are marshalled by the ultravisor. > > > > Signed-off-by: Halil Pasic > > Reviewed-by: Pierre Morel > > Signed-off-by: Michael Mueller > > --- > > drivers/s390/virtio/virtio_ccw.c | 177 +++++++++++++++++++++------------------ > > 1 file changed, 96 insertions(+), 81 deletions(-) > > > > (...) > > > @@ -176,6 +180,22 @@ static struct virtio_ccw_device *to_vc_device(struct virtio_device *vdev) > > return container_of(vdev, struct virtio_ccw_device, vdev); > > } > > > > +static inline void *__vc_dma_alloc(struct virtio_device *vdev, size_t size) > > +{ > > + return ccw_device_dma_zalloc(to_vc_device(vdev)->cdev, size); > > +} > > + > > +static inline void __vc_dma_free(struct virtio_device *vdev, size_t size, > > + void *cpu_addr) > > +{ > > + return ccw_device_dma_free(to_vc_device(vdev)->cdev, cpu_addr, size); > > +} > > + > > +#define vc_dma_alloc_struct(vdev, ptr) \ > > + ({ptr = __vc_dma_alloc(vdev, sizeof(*(ptr))); }) > > +#define vc_dma_free_struct(vdev, ptr) \ > > + __vc_dma_free(vdev, sizeof(*(ptr)), (ptr)) > > + > > I *still* don't like these #defines (and the __vc_dma_* functions), as I > already commented last time. I think they make it harder to follow the > code. > Sorry! I think we simply forgot to address this comment of yours. > > static void drop_airq_indicator(struct virtqueue *vq, struct airq_info *info) > > { > > unsigned long i, flags; > > @@ -336,8 +356,7 @@ static void virtio_ccw_drop_indicator(struct virtio_ccw_device *vcdev, > > struct airq_info *airq_info = vcdev->airq_info; > > > > if (vcdev->is_thinint) { > > - thinint_area = kzalloc(sizeof(*thinint_area), > > - GFP_DMA | GFP_KERNEL); > > + vc_dma_alloc_struct(&vcdev->vdev, thinint_area); > > Last time I wrote: > > "Any reason why this takes a detour via the virtio device? The ccw > device is already referenced in vcdev, isn't it? > > thinint_area = ccw_device_dma_zalloc(vcdev->cdev, sizeof(*thinint_area)); > > looks much more obvious to me." > > It still seems more obvious to me. > The reason why I decided to introduce __vc_dma_alloc() back then is because I had no clarity what do we want to do there. If you take a look the body of __vc_dma_alloc() changed quite a lot, while I the usage not so much. Regarding why is the first argument a pointer struct virtio_device, the idea was probably to keep the needs to be ZONE_DMA and can use the full 64 bit address space separate. But I abandoned the ideal. Also vc_dma_alloc_struct() started out more elaborate (I used to manage a dma_addr_t as well -- see RFC). I'm not quite sure what is your problem with the these. As far as I understand, this is another of those matter of taste things. But it ain't a big deal. I will change this for v4 as you requested. Again sorry for missing it! Regards, Halil > > if (!thinint_area) > > return; > > thinint_area->summary_indicator = >