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Subject[RFC PATCH 1/2] xen/unpopulated-alloc: Introduce helpers for DMA allocations
Date
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

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@epam.com>
---
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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