Virtio-msg May 2025

virtio-msg@lists.linaro.org

1 participants
2 discussions

[PATCH] virtio-mmio: Remove virtqueue list from mmio device

by Viresh Kumar

The MMIO transport implementation creates a list of virtqueues for a virtio device, while the same is already available in the struct virtio_device. Don't create a duplicate list, and use the other one instead. While at it, fix the virtio_device_for_each_vq() macro to accept an argument like "&vm_dev->vdev" (which currently fails to build). Signed-off-by: Viresh Kumar <viresh.kumar(a)linaro.org> --- I have tested this with a Xen/Qemu based setup to test guest to host virtio-i2c communication. Works fine, not sure why this code was added in the first place. drivers/virtio/virtio_mmio.c | 52 +++--------------------------------- include/linux/virtio.h | 2 +- 2 files changed, 4 insertions(+), 50 deletions(-) diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c index 5d78c2d572ab..b152a1eca05a 100644 --- a/drivers/virtio/virtio_mmio.c +++ b/drivers/virtio/virtio_mmio.c @@ -65,7 +65,6 @@ #include <linux/platform_device.h> #include <linux/pm.h> #include <linux/slab.h> -#include <linux/spinlock.h> #include <linux/virtio.h> #include <linux/virtio_config.h> #include <uapi/linux/virtio_mmio.h> @@ -88,22 +87,8 @@ struct virtio_mmio_device { void __iomem *base; unsigned long version; - - /* a list of queues so we can dispatch IRQs */ - spinlock_t lock; - struct list_head virtqueues; -}; - -struct virtio_mmio_vq_info { - /* the actual virtqueue */ - struct virtqueue *vq; - - /* the list node for the virtqueues list */ - struct list_head node; }; - - /* Configuration interface */ static u64 vm_get_features(struct virtio_device *vdev) @@ -300,9 +285,8 @@ static bool vm_notify_with_data(struct virtqueue *vq) static irqreturn_t vm_interrupt(int irq, void *opaque) { struct virtio_mmio_device *vm_dev = opaque; - struct virtio_mmio_vq_info *info; + struct virtqueue *vq; unsigned long status; - unsigned long flags; irqreturn_t ret = IRQ_NONE; /* Read and acknowledge interrupts */ @@ -315,10 +299,8 @@ static irqreturn_t vm_interrupt(int irq, void *opaque) } if (likely(status & VIRTIO_MMIO_INT_VRING)) { - spin_lock_irqsave(&vm_dev->lock, flags); - list_for_each_entry(info, &vm_dev->virtqueues, node) - ret |= vring_interrupt(irq, info->vq); - spin_unlock_irqrestore(&vm_dev->lock, flags); + virtio_device_for_each_vq(&vm_dev->vdev, vq) + ret |= vring_interrupt(irq, vq); } return ret; @@ -329,14 +311,8 @@ static irqreturn_t vm_interrupt(int irq, void *opaque) static void vm_del_vq(struct virtqueue *vq) { struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev); - struct virtio_mmio_vq_info *info = vq->priv; - unsigned long flags; unsigned int index = vq->index; - spin_lock_irqsave(&vm_dev->lock, flags); - list_del(&info->node); - spin_unlock_irqrestore(&vm_dev->lock, flags); - /* Select and deactivate the queue */ writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL); if (vm_dev->version == 1) { @@ -347,8 +323,6 @@ static void vm_del_vq(struct virtqueue *vq) } vring_del_virtqueue(vq); - - kfree(info); } static void vm_del_vqs(struct virtio_device *vdev) @@ -375,9 +349,7 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in { struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev); bool (*notify)(struct virtqueue *vq); - struct virtio_mmio_vq_info *info; struct virtqueue *vq; - unsigned long flags; unsigned int num; int err; @@ -399,13 +371,6 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in goto error_available; } - /* Allocate and fill out our active queue description */ - info = kmalloc(sizeof(*info), GFP_KERNEL); - if (!info) { - err = -ENOMEM; - goto error_kmalloc; - } - num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX); if (num == 0) { err = -ENOENT; @@ -463,13 +428,6 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY); } - vq->priv = info; - info->vq = vq; - - spin_lock_irqsave(&vm_dev->lock, flags); - list_add(&info->node, &vm_dev->virtqueues); - spin_unlock_irqrestore(&vm_dev->lock, flags); - return vq; error_bad_pfn: @@ -481,8 +439,6 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int in writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY); WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY)); } - kfree(info); -error_kmalloc: error_available: return ERR_PTR(err); } @@ -627,8 +583,6 @@ static int virtio_mmio_probe(struct platform_device *pdev) vm_dev->vdev.dev.release = virtio_mmio_release_dev; vm_dev->vdev.config = &virtio_mmio_config_ops; vm_dev->pdev = pdev; - INIT_LIST_HEAD(&vm_dev->virtqueues); - spin_lock_init(&vm_dev->lock); vm_dev->base = devm_platform_ioremap_resource(pdev, 0); if (IS_ERR(vm_dev->base)) { diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 64cb4b04be7a..8b745ce0cf5f 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -196,7 +196,7 @@ int virtio_device_reset_done(struct virtio_device *dev); size_t virtio_max_dma_size(const struct virtio_device *vdev); #define virtio_device_for_each_vq(vdev, vq) \ - list_for_each_entry(vq, &vdev->vqs, list) + list_for_each_entry(vq, &(vdev)->vqs, list) /** * struct virtio_driver - operations for a virtio I/O driver -- 2.31.1.272.g89b43f80a514

2 months

Re: Discussion Virtio with pKVM / FFA

by Viresh Kumar

Hello everyone, Moving the discussion from google doc [1] to email (Sorry, it was becoming impossible to follow and reply there). FWIW, I am not the best person to answer all questions here, that would be Armelle as she understand the requirements and the end goal much better than I do. I can though try to answer from kernel's perspective, based on whatever implementation we have right now. AFAIK, the broad idea is to implement two virtio communication paths from pVM, one to the Linux host (via virtio-pci) and another one to Trusty (via virtio-msg-ffa). In order to not take performance hit at runtime (to map io buffers), the idea is to map whatever amount of memory we can at the beginning and then keep allocating from there. Current setup: What we have achieved until now is virtio-msg communication between host and trusty. We have implemented FFA specific dma-hal [2] to perform FFA memory sharing with trusty. With "reserved-mem" and "memory-region" DT entries (not sure if that is the final solution), we are able to allocate memory the FFA device (which represents bus for all the enumerated devices between trusty/host). This memory is shared with trusty at probe time (from virtio-msg-ffa layer) and the DMA hal later allocates memory from there for coherent allocations and bounce buffers. This works just fine right now. Now looking at "dynamic mapping" section in [1] we are not sure if that will work fine for the end use case, pVM to trusty. It looks like the coco implementation will always end up using dma encrypt/decrypt when a pVM is running and share the memory with host, even when all we want to do is share with trusty. Is that understanding correct ? We would also want to establish virtio-pci (existing tech) based communication between pVM and host, which should use mem decrypt path (?). I am not sure if we need contiguous PA here, contiguous IPA should be sufficient, Armelle? We are also looking for further suggestions to improve the design, as my understanding of memory mapping, dma hal etc. is limited, and maybe there are better ways to do this. -- Viresh [1] https://docs.google.com/document/d/1KyxclKngQ0MShX8Q1YPstZQVIDIctkxfj6lQ0V3… [2] https://web.git.kernel.org/pub/scm/linux/kernel/git/vireshk/linux.git/tree/…

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