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[RFC PATCH 1/2] xen/unpopulated-alloc: Introduce helpers for DMA allocations



From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

Add ability to allocate unpopulated DMAable (contiguous) pages
suitable for grant mapping into. This is going to be used by gnttab
code (see gnttab_dma_alloc_pages()).

TODO: There is a code duplication in fill_dma_pool(). Also pool
oparations likely need to be protected by the lock.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
---
 drivers/xen/unpopulated-alloc.c | 167 ++++++++++++++++++++++++++++++++++++++++
 include/xen/xen.h               |  15 ++++
 2 files changed, 182 insertions(+)

diff --git a/drivers/xen/unpopulated-alloc.c b/drivers/xen/unpopulated-alloc.c
index a39f2d3..bca0198 100644
--- a/drivers/xen/unpopulated-alloc.c
+++ b/drivers/xen/unpopulated-alloc.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/errno.h>
+#include <linux/genalloc.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
@@ -16,6 +17,8 @@ static DEFINE_MUTEX(list_lock);
 static struct page *page_list;
 static unsigned int list_count;
 
+static struct gen_pool *dma_pool;
+
 static struct resource *target_resource;
 
 /*
@@ -230,6 +233,161 @@ void xen_free_unpopulated_pages(unsigned int nr_pages, 
struct page **pages)
 }
 EXPORT_SYMBOL(xen_free_unpopulated_pages);
 
+static int fill_dma_pool(unsigned int nr_pages)
+{
+       struct dev_pagemap *pgmap;
+       struct resource *res, *tmp_res = NULL;
+       void *vaddr;
+       unsigned int alloc_pages = round_up(nr_pages, PAGES_PER_SECTION);
+       struct range mhp_range;
+       int ret;
+
+       res = kzalloc(sizeof(*res), GFP_KERNEL);
+       if (!res)
+               return -ENOMEM;
+
+       res->name = "Xen DMA pool";
+       res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+       mhp_range = mhp_get_pluggable_range(true);
+
+       ret = allocate_resource(target_resource, res,
+                               alloc_pages * PAGE_SIZE, mhp_range.start, 
mhp_range.end,
+                               PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
+       if (ret < 0) {
+               pr_err("Cannot allocate new IOMEM resource\n");
+               goto err_resource;
+       }
+
+       /*
+        * Reserve the region previously allocated from Xen resource to avoid
+        * re-using it by someone else.
+        */
+       if (target_resource != &iomem_resource) {
+               tmp_res = kzalloc(sizeof(*tmp_res), GFP_KERNEL);
+               if (!res) {
+                       ret = -ENOMEM;
+                       goto err_insert;
+               }
+
+               tmp_res->name = res->name;
+               tmp_res->start = res->start;
+               tmp_res->end = res->end;
+               tmp_res->flags = res->flags;
+
+               ret = request_resource(&iomem_resource, tmp_res);
+               if (ret < 0) {
+                       pr_err("Cannot request resource %pR (%d)\n", tmp_res, 
ret);
+                       kfree(tmp_res);
+                       goto err_insert;
+               }
+       }
+
+       pgmap = kzalloc(sizeof(*pgmap), GFP_KERNEL);
+       if (!pgmap) {
+               ret = -ENOMEM;
+               goto err_pgmap;
+       }
+
+       pgmap->type = MEMORY_DEVICE_GENERIC;
+       pgmap->range = (struct range) {
+               .start = res->start,
+               .end = res->end,
+       };
+       pgmap->nr_range = 1;
+       pgmap->owner = res;
+
+       vaddr = memremap_pages(pgmap, NUMA_NO_NODE);
+       if (IS_ERR(vaddr)) {
+               pr_err("Cannot remap memory range\n");
+               ret = PTR_ERR(vaddr);
+               goto err_memremap;
+       }
+
+       ret = gen_pool_add_virt(dma_pool, (unsigned long)vaddr, res->start,
+                       alloc_pages * PAGE_SIZE, NUMA_NO_NODE);
+       if (ret)
+               goto err_pool;
+
+       return 0;
+
+err_pool:
+       memunmap_pages(pgmap);
+err_memremap:
+       kfree(pgmap);
+err_pgmap:
+       if (tmp_res) {
+               release_resource(tmp_res);
+               kfree(tmp_res);
+       }
+err_insert:
+       release_resource(res);
+err_resource:
+       kfree(res);
+       return ret;
+}
+
+/**
+ * xen_alloc_unpopulated_dma_pages - alloc unpopulated DMAable pages
+ * @dev: valid struct device pointer
+ * @nr_pages: Number of pages
+ * @pages: pages returned
+ * @return 0 on success, error otherwise
+ */
+int xen_alloc_unpopulated_dma_pages(struct device *dev, unsigned int nr_pages,
+               struct page **pages)
+{
+       void *vaddr;
+       bool filled = false;
+       unsigned int i;
+       int ret;
+
+       if (!dma_pool)
+               return -ENODEV;
+
+       /* XXX Handle devices which support 64-bit DMA address only for now */
+       if (dma_get_mask(dev) != DMA_BIT_MASK(64))
+               return -EINVAL;
+
+       while (!(vaddr = (void *)gen_pool_alloc(dma_pool, nr_pages * 
PAGE_SIZE))) {
+               if (filled)
+                       return -ENOMEM;
+               else {
+                       ret = fill_dma_pool(nr_pages);
+                       if (ret)
+                               return ret;
+
+                       filled = true;
+               }
+       }
+
+       for (i = 0; i < nr_pages; i++)
+               pages[i] = virt_to_page(vaddr + PAGE_SIZE * i);
+
+       return 0;
+}
+EXPORT_SYMBOL(xen_alloc_unpopulated_dma_pages);
+
+/**
+ * xen_free_unpopulated_dma_pages - return unpopulated DMAable pages
+ * @dev: valid struct device pointer
+ * @nr_pages: Number of pages
+ * @pages: pages to return
+ */
+void xen_free_unpopulated_dma_pages(struct device *dev, unsigned int nr_pages,
+               struct page **pages)
+{
+       void *vaddr;
+
+       if (!dma_pool)
+               return;
+
+       vaddr = page_to_virt(pages[0]);
+
+       gen_pool_free(dma_pool, (unsigned long)vaddr, nr_pages * PAGE_SIZE);
+}
+EXPORT_SYMBOL(xen_free_unpopulated_dma_pages);
+
 static int __init unpopulated_init(void)
 {
        int ret;
@@ -241,8 +399,17 @@ static int __init unpopulated_init(void)
        if (ret) {
                pr_err("xen:unpopulated: Cannot initialize target resource\n");
                target_resource = NULL;
+               return ret;
        }
 
+       dma_pool = gen_pool_create(PAGE_SHIFT, NUMA_NO_NODE);
+       if (!dma_pool) {
+               pr_err("xen:unpopulated: Cannot create DMA pool\n");
+               return -ENOMEM;
+       }
+
+       gen_pool_set_algo(dma_pool, gen_pool_best_fit, NULL);
+
        return ret;
 }
 early_initcall(unpopulated_init);
diff --git a/include/xen/xen.h b/include/xen/xen.h
index a99bab8..a6a7a59 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -52,9 +52,15 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
 extern u64 xen_saved_max_mem_size;
 #endif
 
+struct device;
+
 #ifdef CONFIG_XEN_UNPOPULATED_ALLOC
 int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages);
 void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages);
+int xen_alloc_unpopulated_dma_pages(struct device *dev, unsigned int nr_pages,
+               struct page **pages);
+void xen_free_unpopulated_dma_pages(struct device *dev, unsigned int nr_pages,
+               struct page **pages);
 #include <linux/ioport.h>
 int arch_xen_unpopulated_init(struct resource **res);
 #else
@@ -69,6 +75,15 @@ static inline void xen_free_unpopulated_pages(unsigned int 
nr_pages,
 {
        xen_free_ballooned_pages(nr_pages, pages);
 }
+static inline int xen_alloc_unpopulated_dma_pages(struct device *dev,
+               unsigned int nr_pages, struct page **pages)
+{
+       return -1;
+}
+static inline void xen_free_unpopulated_dma_pages(struct device *dev,
+               unsigned int nr_pages, struct page **pages)
+{
+}
 #endif
 
 #endif /* _XEN_XEN_H */
-- 
2.7.4




 


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