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Tsirkin" To: "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" Cc: Jason Wang , stefanha@redhat.com, sgarzare@redhat.com, eperezma@redhat.com, cohuck@redhat.com, arei.gonglei@huawei.com, yechuan@huawei.com, huangzhichao@huawei.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vdpasim: support doorbell mapping Message-ID: <20221128051555-mutt-send-email-mst@kernel.org> References: <20221128025558.2152-1-longpeng2@huawei.com> <53edc14a-74bb-f9c7-06bd-7ea1047fe613@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <53edc14a-74bb-f9c7-06bd-7ea1047fe613@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 28, 2022 at 04:19:30PM +0800, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote: > > > 在 2022/11/28 12:05, Jason Wang 写道: > > On Mon, Nov 28, 2022 at 10:56 AM Longpeng(Mike) wrote: > > > > > > From: Longpeng > > > > > > Support doorbell mapping for vdpasim devices, then we can test the notify > > > passthrough feature even if there's no real hardware on hand. > > > > You can use vp_vdpa in L1 plus page_ver_vq in L0 to test it in L2. > > That is how I test it. > > > Yes, using nested virtualization can work, but it's hard to deploy in my > working environment for some reasons, so I decided to emulate this > capability in vdpasim, it's much easier. > > > > > > > Allocates a dummy page which used to emulate the notify page of the device. > > > All values written to this page would be ignored, a periodic work will > > > check whether there're requests that need to process. > > > > This seems tricky, it means the device is working even if there's no > > Right. It just try to make the vdpasim device work properly, but the vdpasim > device is only used for testing, so maybe the tricky emulation is > acceptable? Maybe. You can try enabling VIRTIO_F_NOTIFICATION_DATA and then looking at the data written to figure out whether you need to poll the vq. > > kick. If we really want to do, we should try to use page fault handler > > (probably by extending the config ops), but I'm not sure it's worth to > > bother (or if we can find a use case for no simulator devices). > > > This need to modify the framework, it seems unworthy. > > > > > > > This cap is disabled as default, users can enable it as follow: > > > modprobe vdpa_sim notify_passthrough=true > > > > > > Signed-off-by: Longpeng > > > --- > > > drivers/vdpa/vdpa_sim/vdpa_sim.c | 71 ++++++++++++++++++++++++++-- > > > drivers/vdpa/vdpa_sim/vdpa_sim.h | 5 +- > > > drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 5 +- > > > drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 4 +- > > > 4 files changed, 76 insertions(+), 9 deletions(-) > > > > > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c > > > index 7438a89ce939..5c215b56b78b 100644 > > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c > > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c > > > @@ -14,6 +14,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -36,9 +37,15 @@ module_param(max_iotlb_entries, int, 0444); > > > MODULE_PARM_DESC(max_iotlb_entries, > > > "Maximum number of iotlb entries for each address space. 0 means unlimited. (default: 2048)"); > > > > > > +static bool notify_passthrough; > > > +module_param(notify_passthrough, bool, 0444); > > > +MODULE_PARM_DESC(notify_passthrough, > > > + "Enable vq notify(doorbell) area mapping. (default: false)"); > > > + > > > #define VDPASIM_QUEUE_ALIGN PAGE_SIZE > > > #define VDPASIM_QUEUE_MAX 256 > > > #define VDPASIM_VENDOR_ID 0 > > > +#define VDPASIM_VRING_POLL_PERIOD 100 /* ms */ > > > > > > static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa) > > > { > > > @@ -276,7 +283,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr, > > > } > > > > > > vdpasim->dev_attr = *dev_attr; > > > - INIT_WORK(&vdpasim->work, dev_attr->work_fn); > > > + INIT_DELAYED_WORK(&vdpasim->vring_work, dev_attr->work_fn); > > > spin_lock_init(&vdpasim->lock); > > > spin_lock_init(&vdpasim->iommu_lock); > > > > > > @@ -287,6 +294,15 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr, > > > set_dma_ops(dev, &vdpasim_dma_ops); > > > vdpasim->vdpa.mdev = dev_attr->mgmt_dev; > > > > > > + if (notify_passthrough) { > > > + vdpasim->notify = __get_free_page(GFP_KERNEL | __GFP_ZERO); > > > + if (!vdpasim->notify) > > > + goto err_iommu; > > > +#ifdef CONFIG_X86 > > > + set_memory_uc(vdpasim->notify, 1); > > > +#endif > > > > What's the reason for using uc memory? > > > The vma->vm_page_prot of notify mapping is pgprot_noncached (see > vhost_vdpa_fault) but the vdpasim->notify is WB, so we should set its > memtype to UC here and set it back to WB when releasing the device. You never look at this memory though. Why does it matter whether it's UC or WB? > > > + } > > > + > > > vdpasim->config = kzalloc(dev_attr->config_size, GFP_KERNEL); > > > if (!vdpasim->config) > > > goto err_iommu; > > > @@ -357,8 +373,11 @@ static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx) > > > struct vdpasim *vdpasim = vdpa_to_sim(vdpa); > > > struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx]; > > > > > > + if (notify_passthrough) > > > + return; > > > > So we should keep the two paths to be used at the same time. Userspace > > can choose to not map doorbells? > > > It can work even if the userspace does not to map doorbells (e.g start > without page-per-vq=on), because the device will periodic check its vqs. > > > Thanks > > > > > + > > > if (vq->ready) > > > - schedule_work(&vdpasim->work); > > > + schedule_work(&vdpasim->vring_work.work); > > > } > > > > > > static void vdpasim_set_vq_cb(struct vdpa_device *vdpa, u16 idx, > > > @@ -495,6 +514,18 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa) > > > return status; > > > } > > > > > > +static void vdpasim_set_vring_work(struct vdpasim *vdpasim, bool start) > > > +{ > > > + if (!notify_passthrough) > > > + return; > > > + > > > + if (start) > > > + schedule_delayed_work(&vdpasim->vring_work, > > > + msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD)); > > > + else > > > + cancel_delayed_work_sync(&vdpasim->vring_work); > > > +} > > > + > > > static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status) > > > { > > > struct vdpasim *vdpasim = vdpa_to_sim(vdpa); > > > @@ -502,12 +533,16 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status) > > > spin_lock(&vdpasim->lock); > > > vdpasim->status = status; > > > spin_unlock(&vdpasim->lock); > > > + > > > + vdpasim_set_vring_work(vdpasim, status & VIRTIO_CONFIG_S_DRIVER_OK); > > > } > > > > > > static int vdpasim_reset(struct vdpa_device *vdpa, bool clear) > > > { > > > struct vdpasim *vdpasim = vdpa_to_sim(vdpa); > > > > > > + vdpasim_set_vring_work(vdpasim, false); > > > + > > > spin_lock(&vdpasim->lock); > > > vdpasim->status = 0; > > > vdpasim_do_reset(vdpasim); > > > @@ -672,12 +707,24 @@ static int vdpasim_dma_unmap(struct vdpa_device *vdpa, unsigned int asid, > > > return 0; > > > } > > > > > > +static struct vdpa_notification_area > > > +vdpasim_get_vq_notification(struct vdpa_device *vdpa, u16 qid) > > > +{ > > > + struct vdpasim *vdpasim = vdpa_to_sim(vdpa); > > > + struct vdpa_notification_area notify; > > > + > > > + notify.addr = virt_to_phys((void *)vdpasim->notify); > > > + notify.size = PAGE_SIZE; > > > + > > > + return notify; > > > +} > > > + > > > static void vdpasim_free(struct vdpa_device *vdpa) > > > { > > > struct vdpasim *vdpasim = vdpa_to_sim(vdpa); > > > int i; > > > > > > - cancel_work_sync(&vdpasim->work); > > > + cancel_delayed_work_sync(&vdpasim->vring_work); > > > > > > for (i = 0; i < vdpasim->dev_attr.nvqs; i++) { > > > vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov); > > > @@ -693,7 +740,23 @@ static void vdpasim_free(struct vdpa_device *vdpa) > > > vhost_iotlb_free(vdpasim->iommu); > > > kfree(vdpasim->vqs); > > > kfree(vdpasim->config); > > > + if (vdpasim->notify) { > > > +#ifdef CONFIG_X86 > > > + set_memory_wb(vdpasim->notify, 1); > > > +#endif > > > + free_page(vdpasim->notify); > > > + } > > > +} > > > + > > > +void vdpasim_schedule_work(struct vdpasim *vdpasim, bool sched_now) > > > +{ > > > + if (sched_now) > > > + schedule_work(&vdpasim->vring_work.work); > > > + else if (notify_passthrough) > > > + schedule_delayed_work(&vdpasim->vring_work, > > > + msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD)); > > > } > > > +EXPORT_SYMBOL_GPL(vdpasim_schedule_work); > > > > > > static const struct vdpa_config_ops vdpasim_config_ops = { > > > .set_vq_address = vdpasim_set_vq_address, > > > @@ -704,6 +767,7 @@ static const struct vdpa_config_ops vdpasim_config_ops = { > > > .get_vq_ready = vdpasim_get_vq_ready, > > > .set_vq_state = vdpasim_set_vq_state, > > > .get_vq_state = vdpasim_get_vq_state, > > > + .get_vq_notification = vdpasim_get_vq_notification, > > > .get_vq_align = vdpasim_get_vq_align, > > > .get_vq_group = vdpasim_get_vq_group, > > > .get_device_features = vdpasim_get_device_features, > > > @@ -737,6 +801,7 @@ static const struct vdpa_config_ops vdpasim_batch_config_ops = { > > > .get_vq_ready = vdpasim_get_vq_ready, > > > .set_vq_state = vdpasim_set_vq_state, > > > .get_vq_state = vdpasim_get_vq_state, > > > + .get_vq_notification = vdpasim_get_vq_notification, > > > .get_vq_align = vdpasim_get_vq_align, > > > .get_vq_group = vdpasim_get_vq_group, > > > .get_device_features = vdpasim_get_device_features, > > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h > > > index 0e78737dcc16..da0866834918 100644 > > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h > > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h > > > @@ -53,7 +53,7 @@ struct vdpasim_dev_attr { > > > struct vdpasim { > > > struct vdpa_device vdpa; > > > struct vdpasim_virtqueue *vqs; > > > - struct work_struct work; > > > + struct delayed_work vring_work; > > > struct vdpasim_dev_attr dev_attr; > > > /* spinlock to synchronize virtqueue state */ > > > spinlock_t lock; > > > @@ -69,10 +69,13 @@ struct vdpasim { > > > bool running; > > > /* spinlock to synchronize iommu table */ > > > spinlock_t iommu_lock; > > > + /* dummy notify page */ > > > + unsigned long notify; > > > }; > > > > > > struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr, > > > const struct vdpa_dev_set_config *config); > > > +void vdpasim_schedule_work(struct vdpasim *vdpasim, bool sched_now); > > > > > > /* TODO: cross-endian support */ > > > static inline bool vdpasim_is_little_endian(struct vdpasim *vdpasim) > > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c > > > index c6db1a1baf76..8a640ea82284 100644 > > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c > > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c > > > @@ -288,7 +288,7 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim, > > > > > > static void vdpasim_blk_work(struct work_struct *work) > > > { > > > - struct vdpasim *vdpasim = container_of(work, struct vdpasim, work); > > > + struct vdpasim *vdpasim = container_of(work, struct vdpasim, vring_work.work); > > > bool reschedule = false; > > > int i; > > > > > > @@ -325,8 +325,7 @@ static void vdpasim_blk_work(struct work_struct *work) > > > out: > > > spin_unlock(&vdpasim->lock); > > > > > > - if (reschedule) > > > - schedule_work(&vdpasim->work); > > > + vdpasim_schedule_work(vdpasim, reschedule); > > > } > > > > > > static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config) > > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c > > > index c3cb225ea469..8b998952384b 100644 > > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c > > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c > > > @@ -145,7 +145,7 @@ static void vdpasim_handle_cvq(struct vdpasim *vdpasim) > > > > > > static void vdpasim_net_work(struct work_struct *work) > > > { > > > - struct vdpasim *vdpasim = container_of(work, struct vdpasim, work); > > > + struct vdpasim *vdpasim = container_of(work, struct vdpasim, vring_work.work); > > > struct vdpasim_virtqueue *txq = &vdpasim->vqs[1]; > > > struct vdpasim_virtqueue *rxq = &vdpasim->vqs[0]; > > > ssize_t read, write; > > > @@ -196,7 +196,7 @@ static void vdpasim_net_work(struct work_struct *work) > > > vdpasim_net_complete(rxq, write); > > > > > > if (++pkts > 4) { > > > - schedule_work(&vdpasim->work); > > > + vdpasim_schedule_work(vdpasim, true); > > > goto out; > > > } > > > } > > > -- > > > 2.23.0 > > > > > > > .