Re: [PATCH] vdpa_sim: use iova module to allocate IOVA addresses

[Stefano Garzarella <sgarzare@xxxxxxxxxx>]

On Wed, Dec 23, 2020 at 11:43:40AM +0800, Jason Wang wrote:
> On 2020/12/23 上午1:45, Stefano Garzarella wrote:
> > The identical mapping used until now created issues when mapping
> > different virtual pages with the same physical address.
> > To solve this issue, we can use the iova module, to handle the IOVA
> > allocation.
> > For semplicity we use an IOVA allocator with byte granularity.
>
>
> Should be simplicity, so did one comment below.

Right, I'll fix here and in the comment below.

> > We add two new functions, vdpasim_map_range() and vdpasim_unmap_range(),
> > to handle the IOVA allocation and the registration into the IOMMU/IOTLB.
> > These functions are used by dma_map_ops callbacks.
> >
> > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
>
>
> Few nits, but:
>
> Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

Thanks!

> > ---
> >  drivers/vdpa/vdpa_sim/vdpa_sim.h |   2 +
> >  drivers/vdpa/vdpa_sim/vdpa_sim.c | 108 +++++++++++++++++++------------
> >  drivers/vdpa/Kconfig             |   1 +
> >  3 files changed, 69 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > index b02142293d5b..6efe205e583e 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > @@ -6,6 +6,7 @@
> >  #ifndef _VDPA_SIM_H
> >  #define _VDPA_SIM_H
> > +#include <linux/iova.h>
> >  #include <linux/vringh.h>
> >  #include <linux/vdpa.h>
> >  #include <linux/virtio_byteorder.h>
> > @@ -55,6 +56,7 @@ struct vdpasim {
> >  	/* virtio config according to device type */
> >  	void *config;
> >  	struct vhost_iotlb *iommu;
> > +	struct iova_domain iova;
> >  	void *buffer;
> >  	u32 status;
> >  	u32 generation;
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > index b3fcc67bfdf0..341b9daf2ea4 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/vringh.h>
> >  #include <linux/vdpa.h>
> >  #include <linux/vhost_iotlb.h>
> > +#include <linux/iova.h>
> >  #include "vdpa_sim.h"
> > @@ -128,30 +129,57 @@ static int dir_to_perm(enum dma_data_direction dir)
> >  	return perm;
> >  }
> > +static dma_addr_t vdpasim_map_range(struct vdpasim *vdpasim, phys_addr_t paddr,
> > +				    size_t size, unsigned int perm)
> > +{
> > +	struct iova *iova;
> > +	dma_addr_t dma_addr;
> > +	int ret;
> > +
> > +	/* We set the limit_pfn to the maximum (~0UL - 1) */
> > +	iova = alloc_iova(&vdpasim->iova, size, ~0UL - 1, true);
>
>
> Let's use ULONG_MAX?

Definitely, much better!

> > +	if (!iova)
> > +		return DMA_MAPPING_ERROR;
> > +
> > +	dma_addr = iova_dma_addr(&vdpasim->iova, iova);
> > +
> > +	spin_lock(&vdpasim->iommu_lock);
> > +	ret = vhost_iotlb_add_range(vdpasim->iommu, (u64)dma_addr,
> > +				    (u64)dma_addr + size - 1, (u64)paddr, perm);
> > +	spin_unlock(&vdpasim->iommu_lock);
> > +
> > +	if (ret) {
> > +		__free_iova(&vdpasim->iova, iova);
> > +		return DMA_MAPPING_ERROR;
> > +	}
> > +
> > +	return dma_addr;
> > +}
> > +
> > +static void vdpasim_unmap_range(struct vdpasim *vdpasim, dma_addr_t dma_addr,
> > +				size_t size)
> > +{
> > +	spin_lock(&vdpasim->iommu_lock);
> > +	vhost_iotlb_del_range(vdpasim->iommu, (u64)dma_addr,
> > +			      (u64)dma_addr + size - 1);
> > +	spin_unlock(&vdpasim->iommu_lock);
> > +
> > +	free_iova(&vdpasim->iova, iova_pfn(&vdpasim->iova, dma_addr));
> > +}
> > +
> >  static dma_addr_t vdpasim_map_page(struct device *dev, struct page *page,
> >  				   unsigned long offset, size_t size,
> >  				   enum dma_data_direction dir,
> >  				   unsigned long attrs)
> >  {
> >  	struct vdpasim *vdpasim = dev_to_sim(dev);
> > -	struct vhost_iotlb *iommu = vdpasim->iommu;
> > -	u64 pa = (page_to_pfn(page) << PAGE_SHIFT) + offset;
> > -	int ret, perm = dir_to_perm(dir);
> > +	phys_addr_t paddr = page_to_phys(page) + offset;
> > +	int perm = dir_to_perm(dir);
> >  	if (perm < 0)
> >  		return DMA_MAPPING_ERROR;
> > -	/* For simplicity, use identical mapping to avoid e.g iova
> > -	 * allocator.
> > -	 */
> > -	spin_lock(&vdpasim->iommu_lock);
> > -	ret = vhost_iotlb_add_range(iommu, pa, pa + size - 1,
> > -				    pa, dir_to_perm(dir));
> > -	spin_unlock(&vdpasim->iommu_lock);
> > -	if (ret)
> > -		return DMA_MAPPING_ERROR;
> > -
> > -	return (dma_addr_t)(pa);
> > +	return vdpasim_map_range(vdpasim, paddr, size, perm);
> >  }
> >  static void vdpasim_unmap_page(struct device *dev, dma_addr_t dma_addr,
> > @@ -159,12 +187,8 @@ static void vdpasim_unmap_page(struct device *dev, dma_addr_t dma_addr,
> >  			       unsigned long attrs)
> >  {
> >  	struct vdpasim *vdpasim = dev_to_sim(dev);
> > -	struct vhost_iotlb *iommu = vdpasim->iommu;
> > -	spin_lock(&vdpasim->iommu_lock);
> > -	vhost_iotlb_del_range(iommu, (u64)dma_addr,
> > -			      (u64)dma_addr + size - 1);
> > -	spin_unlock(&vdpasim->iommu_lock);
> > +	vdpasim_unmap_range(vdpasim, dma_addr, size);
> >  }
> >  static void *vdpasim_alloc_coherent(struct device *dev, size_t size,
> > @@ -172,27 +196,22 @@ static void *vdpasim_alloc_coherent(struct device *dev, size_t size,
> >  				    unsigned long attrs)
> >  {
> >  	struct vdpasim *vdpasim = dev_to_sim(dev);
> > -	struct vhost_iotlb *iommu = vdpasim->iommu;
> > -	void *addr = kmalloc(size, flag);
> > -	int ret;
> > +	phys_addr_t paddr;
> > +	void *addr;
> > -	spin_lock(&vdpasim->iommu_lock);
> > +	addr = kmalloc(size, flag);
> >  	if (!addr) {
> >  		*dma_addr = DMA_MAPPING_ERROR;
> > -	} else {
> > -		u64 pa = virt_to_phys(addr);
> > -
> > -		ret = vhost_iotlb_add_range(iommu, (u64)pa,
> > -					    (u64)pa + size - 1,
> > -					    pa, VHOST_MAP_RW);
> > -		if (ret) {
> > -			*dma_addr = DMA_MAPPING_ERROR;
> > -			kfree(addr);
> > -			addr = NULL;
> > -		} else
> > -			*dma_addr = (dma_addr_t)pa;
> > +		return NULL;
> > +	}
> > +
> > +	paddr = virt_to_phys(addr);
> > +
> > +	*dma_addr = vdpasim_map_range(vdpasim, paddr, size, VHOST_MAP_RW);
> > +	if (*dma_addr == DMA_MAPPING_ERROR) {
> > +		kfree(addr);
> > +		return NULL;
> >  	}
> > -	spin_unlock(&vdpasim->iommu_lock);
> >  	return addr;
> >  }
> > @@ -202,14 +221,10 @@ static void vdpasim_free_coherent(struct device *dev, size_t size,
> >  				  unsigned long attrs)
> >  {
> >  	struct vdpasim *vdpasim = dev_to_sim(dev);
> > -	struct vhost_iotlb *iommu = vdpasim->iommu;
> > -	spin_lock(&vdpasim->iommu_lock);
> > -	vhost_iotlb_del_range(iommu, (u64)dma_addr,
> > -			      (u64)dma_addr + size - 1);
> > -	spin_unlock(&vdpasim->iommu_lock);
> > +	vdpasim_unmap_range(vdpasim, dma_addr, size);
> > -	kfree(phys_to_virt((uintptr_t)dma_addr));
> > +	kfree(vaddr);
> >  }
> >  static const struct dma_map_ops vdpasim_dma_ops = {
> > @@ -270,6 +285,13 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr)
> >  	for (i = 0; i < dev_attr->nvqs; i++)
> >  		vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu);
> > +	ret = iova_cache_get();
> > +	if (ret)
> > +		goto err_iommu;
> > +
> > +	/* For semplicity we use an IOVA allocator with byte granularity */
>
>
> Should be simplicity.

Fixed :-)

Thanks,
Stefano

> Thanks
>
>
> > +	init_iova_domain(&vdpasim->iova, 1, 0);
> > +
> >  	vdpasim->vdpa.dma_dev = dev;
> >  	return vdpasim;
> > @@ -540,6 +562,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
> >  	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >  	cancel_work_sync(&vdpasim->work);
> > +	put_iova_domain(&vdpasim->iova);
> > +	iova_cache_put();
> >  	kvfree(vdpasim->buffer);
> >  	if (vdpasim->iommu)
> >  		vhost_iotlb_free(vdpasim->iommu);
> > diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
> > index 92a6396f8a73..8965e3717231 100644
> > --- a/drivers/vdpa/Kconfig
> > +++ b/drivers/vdpa/Kconfig
> > @@ -13,6 +13,7 @@ config VDPA_SIM
> >  	depends on RUNTIME_TESTING_MENU && HAS_DMA
> >  	select DMA_OPS
> >  	select VHOST_RING
> > +	select IOMMU_IOVA
> >  	help
> >  	  Enable this module to support vDPA device simulators. These devices
> >  	  are used for testing, prototyping and development of vDPA.

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