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

From: Stefano Garzarella
Date: Tue Dec 22 2020 - 12:47:29 EST

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.

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>
---
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);
+ 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 */
+ 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.
--
2.26.2