From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6B78C433FE for ; Mon, 28 Nov 2022 14:36:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231262AbiK1OgI (ORCPT ); Mon, 28 Nov 2022 09:36:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230115AbiK1OgA (ORCPT ); Mon, 28 Nov 2022 09:36:00 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 228B9BC11 for ; Mon, 28 Nov 2022 06:35:57 -0800 (PST) Received: from kwepemi100025.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4NLSg859M5z15MvB; Mon, 28 Nov 2022 22:35:16 +0800 (CST) Received: from [10.174.148.223] (10.174.148.223) by kwepemi100025.china.huawei.com (7.221.188.158) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 28 Nov 2022 22:35:52 +0800 Message-ID: <97f93d38-c915-d534-44af-b164ca454765@huawei.com> Date: Mon, 28 Nov 2022 22:35:51 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH] vdpasim: support doorbell mapping To: "Michael S. Tsirkin" CC: Jason Wang , , , , , , , , , References: <20221128025558.2152-1-longpeng2@huawei.com> <53edc14a-74bb-f9c7-06bd-7ea1047fe613@huawei.com> <20221128051555-mutt-send-email-mst@kernel.org> <28c1ae52-38ff-42ce-4331-11f7aa040296@huawei.com> <20221128071917-mutt-send-email-mst@kernel.org> <9e9545ab-312c-c9c1-c8ae-8bd6b9f8add6@huawei.com> <20221128084741-mutt-send-email-mst@kernel.org> From: "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" In-Reply-To: <20221128084741-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.148.223] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemi100025.china.huawei.com (7.221.188.158) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/11/28 22:17, Michael S. Tsirkin 写道: > On Mon, Nov 28, 2022 at 09:20:21PM +0800, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote: >> >> >> 在 2022/11/28 20:20, Michael S. Tsirkin 写道: >>> On Mon, Nov 28, 2022 at 07:59:33PM +0800, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote: >>>> >>>> >>>> 在 2022/11/28 18:19, Michael S. Tsirkin 写道: >>>>> 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. >>>>> >>>> We can try after the kernel supports the VIRTIO_F_NOTIFICATION_DATA feature, >>>> while there is still a long way to go. >>> >>> That would be up to you to implement ;) It's probably 10-20 lines of >>> code all in all. >>> >> >> Um...The kick operation won't trigger VMEXIT if we support notify mapping >> for the vdpasim device. >> So, does the vdpasim device has to poll the notify >> address and then decide which VQ to poll? >> The pro of this approach is we can poll the notify address first instead of >> the unconditional poll the VQ, right? > > Right. In fact you can do this without VIRTIO_F_NOTIFICATION_DATA too, > just write 0xffff before checking the vq. > Yes, this can work. I will try it in the next version if there're no other objections. >> >>>>> >>>>>>> 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? >>>>> >>>> >>>> The warning in trace_pfn_remap() would be triggered. >>>> >>>> For example: >>>> >>>> x86/PAT: CPU 16/KVM:17819 map pfn RAM range req uncached-minus for [mem >>>> 0x5151f3000-0x5151f3fff], got write-back >>>> >>>> >>>>>>>> + } >>>>>>>> + >>>>>>>> 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 >>>>>>>> >>>>>>> >>>>>>> . >>>>> >>>>> . >>> >>> . > > .