[PATCH 1/3] memremap.c : Add support for ZONE_DEVICE IO memory with struct pages.

Stephen Bates
2016-10-18T21:42:15Z

From: Logan Gunthorpe <logang@deltatee.com>

We build on recent work that adds memory regions owned by a device
driver (ZONE_DEVICE) [1] and to add struct page support for these new
regions of memory [2].

1. Add an extra flags argument into dev_memremap_pages to take in a
MEMREMAP_XX argument. We update the existing calls to this function to
reflect the change.

2. For completeness, we add MEMREMAP_WT support to the memremap;
however we have no actual need for this functionality.

3. We add the static functions, add_zone_device_pages and
remove_zone_device pages. These are similar to arch_add_memory except
they don't create the memory mapping. We don't believe these need to be
made arch specific, but are open to other opinions.

4. dev_memremap_pages and devm_memremap_pages_release are updated to
treat IO memory slightly differently. For IO memory we use a combination
of the appropriate io_remap function and the zone_device pages functions
created above. A flags variable and kaddr pointer are added to struct
page_mem to facilitate this for the release function. We also set up
the page attribute tables for the mapped region correctly based on the
desired mapping.

[1] https://lists.01.org/pipermail/linux-nvdimm/2015-August/001810.html
[2] https://lists.01.org/pipermail/linux-nvdimm/2015-October/002387.html

Signed-off-by: Stephen Bates <sbates@raithlin.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
drivers/dax/pmem.c | 4 +-
drivers/nvdimm/pmem.c | 4 +-
include/linux/memremap.h | 5 ++-
kernel/memremap.c | 80 +++++++++++++++++++++++++++++++++++++--
tools/testing/nvdimm/test/iomap.c | 3 +-
5 files changed, 86 insertions(+), 10 deletions(-)

diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index 9630d88..58ac456 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -14,6 +14,7 @@
#include <linux/memremap.h>
#include <linux/module.h>
#include <linux/pfn_t.h>
+#include <linux/pmem.h>
#include "../nvdimm/pfn.h"
#include "../nvdimm/nd.h"
#include "dax.h"
@@ -108,7 +109,8 @@ static int dax_pmem_probe(struct device *dev)
if (rc)
return rc;

- addr = devm_memremap_pages(dev, &res, &dax_pmem->ref, altmap);
+ addr = devm_memremap_pages(dev, &res, &dax_pmem->ref, altmap,
+ ARCH_MEMREMAP_PMEM);
if (IS_ERR(addr))
return PTR_ERR(addr);

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 42b3a82..97032a1 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -278,7 +278,7 @@ static int pmem_attach_disk(struct device *dev,
pmem->pfn_flags = PFN_DEV;
if (is_nd_pfn(dev)) {
addr = devm_memremap_pages(dev, &pfn_res, &q->q_usage_counter,
- altmap);
+ altmap, ARCH_MEMREMAP_PMEM);
pfn_sb = nd_pfn->pfn_sb;
pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
pmem->pfn_pad = resource_size(res) - resource_size(&pfn_res);
@@ -287,7 +287,7 @@ static int pmem_attach_disk(struct device *dev,
res->start += pmem->data_offset;
} else if (pmem_should_map_pages(dev)) {
addr = devm_memremap_pages(dev, &nsio->res,
- &q->q_usage_counter, NULL);
+ &q->q_usage_counter, NULL, ARCH_MEMREMAP_PMEM);
pmem->pfn_flags |= PFN_MAP;
} else
addr = devm_memremap(dev, pmem->phys_addr,
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 9341619..fc99283 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -51,12 +51,13 @@ struct dev_pagemap {

#ifdef CONFIG_ZONE_DEVICE
void *devm_memremap_pages(struct device *dev, struct resource *res,
- struct percpu_ref *ref, struct vmem_altmap *altmap);
+ struct percpu_ref *ref, struct vmem_altmap *altmap,
+ unsigned long flags);
struct dev_pagemap *find_dev_pagemap(resource_size_t phys);
#else
static inline void *devm_memremap_pages(struct device *dev,
struct resource *res, struct percpu_ref *ref,
- struct vmem_altmap *altmap)
+ struct vmem_altmap *altmap, unsigned long flags)
{
/*
* Fail attempts to call devm_memremap_pages() without
diff --git a/kernel/memremap.c b/kernel/memremap.c
index b501e39..d5f462c 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -175,13 +175,41 @@ static RADIX_TREE(pgmap_radix, GFP_KERNEL);
#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)

+enum {
+ PAGEMAP_IO_MEM = 1 << 0,
+};
+
struct page_map {
struct resource res;
struct percpu_ref *ref;
struct dev_pagemap pgmap;
struct vmem_altmap altmap;
+ void *kaddr;
+ int flags;
};

+static int add_zone_device_pages(int nid, u64 start, u64 size)
+{
+ struct pglist_data *pgdat = NODE_DATA(nid);
+ struct zone *zone = pgdat->node_zones + ZONE_DEVICE;
+ unsigned long start_pfn = start >> PAGE_SHIFT;
+ unsigned long nr_pages = size >> PAGE_SHIFT;
+
+ return __add_pages(nid, zone, start_pfn, nr_pages);
+}
+
+static void remove_zone_device_pages(u64 start, u64 size)
+{
+ unsigned long start_pfn = start >> PAGE_SHIFT;
+ unsigned long nr_pages = size >> PAGE_SHIFT;
+ struct zone *zone;
+ int ret;
+
+ zone = page_zone(pfn_to_page(start_pfn));
+ ret = __remove_pages(zone, start_pfn, nr_pages);
+ WARN_ON_ONCE(ret);
+}
+
void get_zone_device_page(struct page *page)
{
percpu_ref_get(page->pgmap->ref);
@@ -246,9 +274,17 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
/* pages are dead and unused, undo the arch mapping */
align_start = res->start & ~(SECTION_SIZE - 1);
align_size = ALIGN(resource_size(res), SECTION_SIZE);
- arch_remove_memory(align_start, align_size);
+
+ if (page_map->flags & PAGEMAP_IO_MEM) {
+ remove_zone_device_pages(align_start, align_size);
+ iounmap(page_map->kaddr);
+ } else {
+ arch_remove_memory(align_start, align_size);
+ }
+
untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
pgmap_radix_release(res);
+
dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
"%s: failed to free all reserved pages\n", __func__);
}
@@ -270,6 +306,8 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
* @res: "host memory" address range
* @ref: a live per-cpu reference count
* @altmap: optional descriptor for allocating the memmap from @res
+ * @flags: either MEMREMAP_WB, MEMREMAP_WT and MEMREMAP_WC
+ * see memremap() for a description of the flags
*
* Notes:
* 1/ @ref must be 'live' on entry and 'dead' before devm_memunmap_pages() time
@@ -280,7 +318,8 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
* this is not enforced.
*/
void *devm_memremap_pages(struct device *dev, struct resource *res,
- struct percpu_ref *ref, struct vmem_altmap *altmap)
+ struct percpu_ref *ref, struct vmem_altmap *altmap,
+ unsigned long flags)
{
resource_size_t key, align_start, align_size, align_end;
pgprot_t pgprot = PAGE_KERNEL;
@@ -288,6 +327,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
struct page_map *page_map;
int error, nid, is_ram;
unsigned long pfn;
+ void *addr = NULL;
+ enum page_cache_mode pcm;

align_start = res->start & ~(SECTION_SIZE - 1);
align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
@@ -353,15 +394,44 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
if (nid < 0)
nid = numa_mem_id();

+ if (flags & MEMREMAP_WB)
+ pcm = _PAGE_CACHE_MODE_WB;
+ else if (flags & MEMREMAP_WT)
+ pcm = _PAGE_CACHE_MODE_WT;
+ else if (flags & MEMREMAP_WC)
+ pcm = _PAGE_CACHE_MODE_WC;
+ else
+ pcm = _PAGE_CACHE_MODE_WB;
+
+ pgprot = __pgprot(pgprot_val(pgprot) | cachemode2protval(pcm));
+
error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
align_size);
if (error)
goto err_pfn_remap;

- error = arch_add_memory(nid, align_start, align_size, true);
+ if (flags & MEMREMAP_WB || !flags) {
+ error = arch_add_memory(nid, align_start, align_size, true);
+ addr = __va(res->start);
+ } else {
+ page_map->flags |= PAGEMAP_IO_MEM;
+ error = add_zone_device_pages(nid, align_start, align_size);
+ }
+
if (error)
goto err_add_memory;

+ if (!addr && (flags & MEMREMAP_WT))
+ addr = ioremap_wt(res->start, resource_size(res));
+
+ if (!addr && (flags & MEMREMAP_WC))
+ addr = ioremap_wc(res->start, resource_size(res));
+
+ if (!addr && page_map->flags & PAGEMAP_IO_MEM) {
+ remove_zone_device_pages(res->start, resource_size(res));
+ goto err_add_memory;
+ }
+
for_each_device_pfn(pfn, page_map) {
struct page *page = pfn_to_page(pfn);

@@ -374,8 +444,10 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
list_del(&page->lru);
page->pgmap = pgmap;
}
+
+ page_map->kaddr = addr;
devres_add(dev, page_map);
- return __va(res->start);
+ return addr;

err_add_memory:
untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index 3ccef73..b82fecb 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -17,6 +17,7 @@
#include <linux/module.h>
#include <linux/types.h>
#include <linux/pfn_t.h>
+#include <linux/pmem.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/mm.h>
@@ -109,7 +110,7 @@ void *__wrap_devm_memremap_pages(struct device *dev, struct resource *res,

if (nfit_res)
return nfit_res->buf + offset - nfit_res->res.start;
- return devm_memremap_pages(dev, res, ref, altmap);
+ return devm_memremap_pages(dev, res, ref, altmap, ARCH_MEMREMAP_PMEM);
}
EXPORT_SYMBOL(__wrap_devm_memremap_pages);

--
2.1.4

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