[PATCH 6/8] iommu: allow the dma-iommu api to use bounce buffers

Tom Murphy
2019-12-21T15:04:55Z

Allow the dma-iommu api to use bounce buffers for untrusted devices.
This is a copy of the intel bounce buffer code.

Signed-off-by: Tom Murphy <murphyt7@tcd.ie>
---
drivers/iommu/dma-iommu.c | 93 ++++++++++++++++++++++++++++++++-------
drivers/iommu/iommu.c | 10 +++++
include/linux/iommu.h | 9 +++-
3 files changed, 95 insertions(+), 17 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 4eac3cd35443..cf778db7d84d 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -20,9 +20,11 @@
#include <linux/irq.h>
#include <linux/mm.h>
#include <linux/pci.h>
+#include <linux/swiotlb.h>
#include <linux/scatterlist.h>
#include <linux/vmalloc.h>
#include <linux/crash_dump.h>
+#include <linux/dma-direct.h>

struct iommu_dma_msi_page {
struct list_head list;
@@ -505,29 +507,89 @@ static void __iommu_dma_unmap(struct device *dev, dma_addr_t dma_addr,
iommu_tlb_sync(domain, &iotlb_gather);
}

+
iommu_dma_free_iova(cookie, dma_addr, size, freelist);
}

+static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr,
+ size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ struct iommu_domain *domain = iommu_get_dma_domain(dev);
+ struct iommu_dma_cookie *cookie = domain->iova_cookie;
+ struct iova_domain *iovad = &cookie->iovad;
+ size_t iova_off = iova_offset(iovad, dma_addr);
+ size_t aligned_size = iova_align(iovad, size + iova_off);
+ phys_addr_t phys;
+
+ phys = iommu_iova_to_phys(domain, dma_addr);
+ if (WARN_ON(!phys))
+ return;
+
+ __iommu_dma_unmap(dev, dma_addr, size);
+
+#ifdef CONFIG_SWIOTLB
+ if (unlikely(is_swiotlb_buffer(phys)))
+ swiotlb_tbl_unmap_single(dev, phys, size,
+ aligned_size, dir, attrs);
+#endif
+}
+
static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
- size_t size, int prot, dma_addr_t dma_mask)
+ size_t org_size, dma_addr_t dma_mask, bool coherent,
+ enum dma_data_direction dir, unsigned long attrs)
{
+ int prot = dma_info_to_prot(dir, coherent, attrs);
struct iommu_domain *domain = iommu_get_dma_domain(dev);
struct iommu_dma_cookie *cookie = domain->iova_cookie;
struct iova_domain *iovad = &cookie->iovad;
size_t iova_off = iova_offset(iovad, phys);
+ size_t aligned_size = iova_align(iovad, org_size + iova_off);
dma_addr_t iova;

if (unlikely(iommu_dma_deferred_attach(dev, domain)))
return DMA_MAPPING_ERROR;

- size = iova_align(iovad, size + iova_off);
+#ifdef CONFIG_SWIOTLB
+ /*
+ * If both the physical buffer start address and size are
+ * page aligned, we don't need to use a bounce page.
+ */
+ if (iommu_needs_bounce_buffer(dev)
+ && !iova_offset(iovad, phys | org_size)) {
+ phys = swiotlb_tbl_map_single(dev,
+ __phys_to_dma(dev, io_tlb_start),
+ phys, org_size, aligned_size, dir, attrs);
+
+ if (phys == DMA_MAPPING_ERROR)
+ return DMA_MAPPING_ERROR;
+
+ /* Cleanup the padding area. */
+ void *padding_start = phys_to_virt(phys);
+ size_t padding_size = aligned_size;
+
+ if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
+ (dir == DMA_TO_DEVICE ||
+ dir == DMA_BIDIRECTIONAL)) {
+ padding_start += org_size;
+ padding_size -= org_size;
+ }

- iova = iommu_dma_alloc_iova(domain, size, dma_mask, dev);
+ memset(padding_start, 0, padding_size);
+ }
+#endif
+
+ iova = iommu_dma_alloc_iova(domain, aligned_size, dma_mask, dev);
if (!iova)
return DMA_MAPPING_ERROR;

- if (iommu_map_atomic(domain, iova, phys - iova_off, size, prot)) {
- iommu_dma_free_iova(cookie, iova, size, NULL);
+ if (iommu_map_atomic(domain, iova, phys - iova_off, aligned_size,
+ prot)) {
+
+ if (unlikely(is_swiotlb_buffer(phys)))
+ swiotlb_tbl_unmap_single(dev, phys, aligned_size,
+ aligned_size, dir, attrs);
+ iommu_dma_free_iova(cookie, iova, aligned_size, NULL);
return DMA_MAPPING_ERROR;
}
return iova + iova_off;
@@ -761,10 +823,10 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
{
phys_addr_t phys = page_to_phys(page) + offset;
bool coherent = dev_is_dma_coherent(dev);
- int prot = dma_info_to_prot(dir, coherent, attrs);
dma_addr_t dma_handle;

- dma_handle = __iommu_dma_map(dev, phys, size, prot, dma_get_mask(dev));
+ dma_handle = __iommu_dma_map(dev, phys, size, dma_get_mask(dev),
+ coherent, dir, attrs);
if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
dma_handle != DMA_MAPPING_ERROR)
arch_sync_dma_for_device(phys, size, dir);
@@ -776,7 +838,7 @@ static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
{
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir);
- __iommu_dma_unmap(dev, dma_handle, size);
+ __iommu_dma_unmap_swiotlb(dev, dma_handle, size, dir, attrs);
}

/*
@@ -960,21 +1022,20 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
sg = tmp;
}
end = sg_dma_address(sg) + sg_dma_len(sg);
- __iommu_dma_unmap(dev, start, end - start);
+ __iommu_dma_unmap_swiotlb(dev, start, end - start, dir, attrs);
}

static dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
- return __iommu_dma_map(dev, phys, size,
- dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO,
- dma_get_mask(dev));
+ return __iommu_dma_map(dev, phys, size, dma_get_mask(dev), false, dir,
+ attrs);
}

static void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
- __iommu_dma_unmap(dev, handle, size);
+ __iommu_dma_unmap_swiotlb(dev, handle, size, dir, attrs);
}

static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
@@ -1056,7 +1117,6 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
{
bool coherent = dev_is_dma_coherent(dev);
- int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
struct page *page = NULL;
void *cpu_addr;

@@ -1074,8 +1134,9 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
if (!cpu_addr)
return NULL;

- *handle = __iommu_dma_map(dev, page_to_phys(page), size, ioprot,
- dev->coherent_dma_mask);
+ *handle = __iommu_dma_map(dev, page_to_phys(page), size,
+ dev->coherent_dma_mask, coherent, DMA_BIDIRECTIONAL,
+ attrs);
if (*handle == DMA_MAPPING_ERROR) {
__iommu_dma_free(dev, size, cpu_addr);
return NULL;
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index cec728f40d9c..e5653cb20c83 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2236,6 +2236,16 @@ void iommu_get_resv_regions(struct device *dev, struct list_head *list)
ops->get_resv_regions(dev, list);
}

+int iommu_needs_bounce_buffer(struct device *dev)
+{
+ const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+ if (ops && ops->needs_bounce_buffer)
+ return ops->needs_bounce_buffer(dev);
+
+ return 0;
+}
+
void iommu_put_resv_regions(struct device *dev, struct list_head *list)
{
const struct iommu_ops *ops = dev->bus->iommu_ops;
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 61cac25410b5..d377ffa362a7 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -280,6 +280,7 @@ struct iommu_ops {
enum iommu_attr attr, void *data);
int (*domain_set_attr)(struct iommu_domain *domain,
enum iommu_attr attr, void *data);
+ int (*needs_bounce_buffer)(struct device *dev);

/* Request/Free a list of reserved regions for a device */
void (*get_resv_regions)(struct device *dev, struct list_head *list);
@@ -460,6 +461,7 @@ extern phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, dma_addr_t io
extern void iommu_set_fault_handler(struct iommu_domain *domain,
iommu_fault_handler_t handler, void *token);

+extern int iommu_needs_bounce_buffer(struct device *dev);
extern void iommu_get_resv_regions(struct device *dev, struct list_head *list);
extern void iommu_put_resv_regions(struct device *dev, struct list_head *list);
extern int iommu_request_dm_for_dev(struct device *dev);
@@ -530,7 +532,7 @@ static inline void iommu_flush_iotlb_all(struct iommu_domain *domain)
domain->ops->flush_iotlb_all(domain);
}

-static inline void flush_iotlb_range(struct iommu_domain *domain,
+static inline void iommu_flush_iotlb_range(struct iommu_domain *domain,
unsigned long iova, size_t size,
struct page *freelist)
{
@@ -764,6 +766,11 @@ static inline void iommu_set_fault_handler(struct iommu_domain *domain,
{
}

+static inline int iommu_needs_bounce_buffer(struct device *dev)
+{
+ return 0;
+}
+
static inline void iommu_get_resv_regions(struct device *dev,
struct list_head *list)
{
--
2.20.1