@@ -161,6 +161,20 @@ config XEN_GRANT_DEV_ALLOC
to other domains. This can be used to implement frontend drivers
or as part of an inter-domain shared memory channel.
+config XEN_GRANT_DMA_ALLOC
+ bool "Allow allocating DMA capable buffers with grant reference module"
+ depends on XEN && HAS_DMA
+ help
+ Extends grant table module API to allow allocating DMA capable
+ buffers and mapping foreign grant references on top of it.
+ The resulting buffer is similar to one allocated by the balloon
+ driver in that proper memory reservation is made by
+ ({increase|decrease}_reservation and VA mappings are updated if
+ needed).
+ This is useful for sharing foreign buffers with HW drivers which
+ cannot work with scattered buffers provided by the balloon driver,
+ but require DMAable memory instead.
+
config SWIOTLB_XEN
def_bool y
select SWIOTLB
@@ -45,6 +45,9 @@
#include <linux/workqueue.h>
#include <linux/ratelimit.h>
#include <linux/moduleparam.h>
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+#include <linux/dma-mapping.h>
+#endif
#include <xen/xen.h>
#include <xen/interface/xen.h>
@@ -57,6 +60,7 @@
#ifdef CONFIG_X86
#include <asm/xen/cpuid.h>
#endif
+#include <xen/mem-reservation.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/interface.h>
@@ -838,6 +842,99 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
}
EXPORT_SYMBOL_GPL(gnttab_free_pages);
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+/**
+ * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
+ * @args: arguments to the function
+ */
+int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
+{
+ unsigned long pfn, start_pfn;
+ size_t size;
+ int i, ret;
+
+ size = args->nr_pages << PAGE_SHIFT;
+ if (args->coherent)
+ args->vaddr = dma_alloc_coherent(args->dev, size,
+ &args->dev_bus_addr,
+ GFP_KERNEL | __GFP_NOWARN);
+ else
+ args->vaddr = dma_alloc_wc(args->dev, size,
+ &args->dev_bus_addr,
+ GFP_KERNEL | __GFP_NOWARN);
+ if (!args->vaddr) {
+ pr_debug("Failed to allocate DMA buffer of size %zu\n", size);
+ return -ENOMEM;
+ }
+
+ start_pfn = __phys_to_pfn(args->dev_bus_addr);
+ for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
+ pfn++, i++) {
+ struct page *page = pfn_to_page(pfn);
+
+ args->pages[i] = page;
+ args->frames[i] = xen_page_to_gfn(page);
+ xenmem_reservation_scrub_page(page);
+ }
+
+ xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);
+
+ ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
+ if (ret != args->nr_pages) {
+ pr_debug("Failed to decrease reservation for DMA buffer\n");
+ ret = -EFAULT;
+ goto fail;
+ }
+
+ ret = gnttab_pages_set_private(args->nr_pages, args->pages);
+ if (ret < 0)
+ goto fail;
+
+ return 0;
+
+fail:
+ gnttab_dma_free_pages(args);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);
+
+/**
+ * gnttab_dma_free_pages - free DMAable pages
+ * @args: arguments to the function
+ */
+int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
+{
+ size_t size;
+ int i, ret;
+
+ gnttab_pages_clear_private(args->nr_pages, args->pages);
+
+ for (i = 0; i < args->nr_pages; i++)
+ args->frames[i] = page_to_xen_pfn(args->pages[i]);
+
+ ret = xenmem_reservation_increase(args->nr_pages, args->frames);
+ if (ret != args->nr_pages) {
+ pr_debug("Failed to decrease reservation for DMA buffer\n");
+ ret = -EFAULT;
+ } else {
+ ret = 0;
+ }
+
+ xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
+ args->frames);
+
+ size = args->nr_pages << PAGE_SHIFT;
+ if (args->coherent)
+ dma_free_coherent(args->dev, size,
+ args->vaddr, args->dev_bus_addr);
+ else
+ dma_free_wc(args->dev, size,
+ args->vaddr, args->dev_bus_addr);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
+#endif
+
/* Handling of paged out grant targets (GNTST_eagain) */
#define MAX_DELAY 256
static inline void
@@ -198,6 +198,24 @@ void gnttab_free_auto_xlat_frames(void);
int gnttab_alloc_pages(int nr_pages, struct page **pages);
void gnttab_free_pages(int nr_pages, struct page **pages);
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+struct gnttab_dma_alloc_args {
+ /* Device for which DMA memory will be/was allocated. */
+ struct device *dev;
+ /* If set then DMA buffer is coherent and write-combine otherwise. */
+ bool coherent;
+
+ int nr_pages;
+ struct page **pages;
+ xen_pfn_t *frames;
+ void *vaddr;
+ dma_addr_t dev_bus_addr;
+};
+
+int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
+int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
+#endif
+
int gnttab_pages_set_private(int nr_pages, struct page **pages);
void gnttab_pages_clear_private(int nr_pages, struct page **pages);