nd_blk: change aperture mapping from WC to WB

This should result in a pretty sizeable performance gain for reads.  For
rough comparison I did some simple read testing using PMEM to compare
reads of write combining (WC) mappings vs write-back (WB).  This was
done on a random lab machine.

PMEM reads from a write combining mapping:
	# dd of=/dev/null if=/dev/pmem0 bs=4096 count=100000
	100000+0 records in
	100000+0 records out
	409600000 bytes (410 MB) copied, 9.2855 s, 44.1 MB/s

PMEM reads from a write-back mapping:
	# dd of=/dev/null if=/dev/pmem0 bs=4096 count=1000000
	1000000+0 records in
	1000000+0 records out
	4096000000 bytes (4.1 GB) copied, 3.44034 s, 1.2 GB/s

To be able to safely support a write-back aperture I needed to add
support for the "read flush" _DSM flag, as outlined in the DSM spec:

http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

This flag tells the ND BLK driver that it needs to flush the cache lines
associated with the aperture after the aperture is moved but before any
new data is read.  This ensures that any stale cache lines from the
previous contents of the aperture will be discarded from the processor
cache, and the new data will be read properly from the DIMM.  We know
that the cache lines are clean and will be discarded without any
writeback because either a) the previous aperture operation was a read,
and we never modified the contents of the aperture, or b) the previous
aperture operation was a write and we must have written back the dirtied
contents of the aperture to the DIMM before the I/O was completed.

In order to add support for the "read flush" flag I needed to add a
generic routine to invalidate cache lines, mmio_flush_range().  This is
protected by the ARCH_HAS_MMIO_FLUSH Kconfig variable, and is currently
only supported on x86.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b3a1a5d77d92c2fd1d1d1a3b0b0b898944e8cd5b..5d4980e6bc4f082adde371e311817b5c5df78509 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -28,6 +28,7 @@ config X86
        select ARCH_HAS_FAST_MULTIPLIER
        select ARCH_HAS_GCOV_PROFILE_ALL
        select ARCH_HAS_PMEM_API
+       select ARCH_HAS_MMIO_FLUSH
        select ARCH_HAS_SG_CHAIN
        select ARCH_HAVE_NMI_SAFE_CMPXCHG
        select ARCH_MIGHT_HAVE_ACPI_PDC         if ACPI

diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 471418ac1ff951f903eb6c6a88084e7dcc9de765..e63aa38e85fb23375ecefa40efe8cd9d76da6c43 100644 (file)
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -89,6 +89,8 @@ int set_pages_rw(struct page *page, int numpages);
 
 void clflush_cache_range(void *addr, unsigned int size);
 
+#define mmio_flush_range(addr, size) clflush_cache_range(addr, size)
+
 #ifdef CONFIG_DEBUG_RODATA
 void mark_rodata_ro(void);
 extern const int rodata_test_data;

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index d241fbd5c87b2f890d0d06b8943f42b862c6fd94..83ec9b1d77cc17eecb4281118290bbb278ecc273 100644 (file)
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -248,8 +248,6 @@ static inline void flush_write_buffers(void)
 #endif
 }
 
-#define ARCH_MEMREMAP_PMEM MEMREMAP_WB
-
 #endif /* __KERNEL__ */
 
 extern void native_io_delay(void);

diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
index a3a0df6545eef18a05f717d74851c1bc84a516ea..bb026c5adf8a88156015e4ac3eec4bb741f1a765 100644 (file)
--- a/arch/x86/include/asm/pmem.h
+++ b/arch/x86/include/asm/pmem.h
@@ -18,6 +18,8 @@
 #include <asm/cpufeature.h>
 #include <asm/special_insns.h>
 
+#define ARCH_MEMREMAP_PMEM MEMREMAP_WB
+
 #ifdef CONFIG_ARCH_HAS_PMEM_API
 /**
  * arch_memcpy_to_pmem - copy data to persistent memory

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 114cf48085abd34eacb341fae1f246e2fdfb4b41..4baeb853e0c370be8704a10eea1c12d78629b52e 100644 (file)
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -410,6 +410,7 @@ config ACPI_NFIT
        tristate "ACPI NVDIMM Firmware Interface Table (NFIT)"
        depends on PHYS_ADDR_T_64BIT
        depends on BLK_DEV
+       depends on ARCH_HAS_MMIO_FLUSH
        select LIBNVDIMM
        help
          Infrastructure to probe ACPI 6 compliant platforms for

diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
index 7c2638f914a9094102304e2abbc7ee492300726a..56fff014163699c11719839442132a8fa7609c7b 100644 (file)
--- a/drivers/acpi/nfit.c
+++ b/drivers/acpi/nfit.c
@@ -1017,7 +1017,7 @@ static u64 read_blk_stat(struct nfit_blk *nfit_blk, unsigned int bw)
        if (mmio->num_lines)
                offset = to_interleave_offset(offset, mmio);
 
-       return readq(mmio->base + offset);
+       return readq(mmio->addr.base + offset);
 }
 
 static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
@@ -1042,11 +1042,11 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
        if (mmio->num_lines)
                offset = to_interleave_offset(offset, mmio);
 
-       writeq(cmd, mmio->base + offset);
+       writeq(cmd, mmio->addr.base + offset);
        wmb_blk(nfit_blk);
 
        if (nfit_blk->dimm_flags & ND_BLK_DCR_LATCH)
-               readq(mmio->base + offset);
+               readq(mmio->addr.base + offset);
 }
 
 static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
@@ -1078,11 +1078,16 @@ static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
                }
 
                if (rw)
-                       memcpy_to_pmem(mmio->aperture + offset,
+                       memcpy_to_pmem(mmio->addr.aperture + offset,
                                        iobuf + copied, c);
-               else
+               else {
+                       if (nfit_blk->dimm_flags & ND_BLK_READ_FLUSH)
+                               mmio_flush_range((void __force *)
+                                       mmio->addr.aperture + offset, c);
+
                        memcpy_from_pmem(iobuf + copied,
-                                       mmio->aperture + offset, c);
+                                       mmio->addr.aperture + offset, c);
+               }
 
                copied += c;
                len -= c;
@@ -1129,7 +1134,10 @@ static void nfit_spa_mapping_release(struct kref *kref)
 
        WARN_ON(!mutex_is_locked(&acpi_desc->spa_map_mutex));
        dev_dbg(acpi_desc->dev, "%s: SPA%d\n", __func__, spa->range_index);
-       iounmap(spa_map->iomem);
+       if (spa_map->type == SPA_MAP_APERTURE)
+               memunmap((void __force *)spa_map->addr.aperture);
+       else
+               iounmap(spa_map->addr.base);
        release_mem_region(spa->address, spa->length);
        list_del(&spa_map->list);
        kfree(spa_map);
@@ -1175,7 +1183,7 @@ static void __iomem *__nfit_spa_map(struct acpi_nfit_desc *acpi_desc,
        spa_map = find_spa_mapping(acpi_desc, spa);
        if (spa_map) {
                kref_get(&spa_map->kref);
-               return spa_map->iomem;
+               return spa_map->addr.base;
        }
 
        spa_map = kzalloc(sizeof(*spa_map), GFP_KERNEL);
@@ -1191,20 +1199,19 @@ static void __iomem *__nfit_spa_map(struct acpi_nfit_desc *acpi_desc,
        if (!res)
                goto err_mem;
 
-       if (type == SPA_MAP_APERTURE) {
-               /*
-                * TODO: memremap_pmem() support, but that requires cache
-                * flushing when the aperture is moved.
-                */
-               spa_map->iomem = ioremap_wc(start, n);
-       } else
-               spa_map->iomem = ioremap_nocache(start, n);
+       spa_map->type = type;
+       if (type == SPA_MAP_APERTURE)
+               spa_map->addr.aperture = (void __pmem *)memremap(start, n,
+                                                       ARCH_MEMREMAP_PMEM);
+       else
+               spa_map->addr.base = ioremap_nocache(start, n);
+
 
-       if (!spa_map->iomem)
+       if (!spa_map->addr.base)
                goto err_map;
 
        list_add_tail(&spa_map->list, &acpi_desc->spa_maps);
-       return spa_map->iomem;
+       return spa_map->addr.base;
 
  err_map:
        release_mem_region(start, n);
@@ -1267,7 +1274,7 @@ static int acpi_nfit_blk_get_flags(struct nvdimm_bus_descriptor *nd_desc,
                nfit_blk->dimm_flags = flags.flags;
        else if (rc == -ENOTTY) {
                /* fall back to a conservative default */
-               nfit_blk->dimm_flags = ND_BLK_DCR_LATCH;
+               nfit_blk->dimm_flags = ND_BLK_DCR_LATCH | ND_BLK_READ_FLUSH;
                rc = 0;
        } else
                rc = -ENXIO;
@@ -1307,9 +1314,9 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
        /* map block aperture memory */
        nfit_blk->bdw_offset = nfit_mem->bdw->offset;
        mmio = &nfit_blk->mmio[BDW];
-       mmio->base = nfit_spa_map(acpi_desc, nfit_mem->spa_bdw,
+       mmio->addr.base = nfit_spa_map(acpi_desc, nfit_mem->spa_bdw,
                        SPA_MAP_APERTURE);
-       if (!mmio->base) {
+       if (!mmio->addr.base) {
                dev_dbg(dev, "%s: %s failed to map bdw\n", __func__,
                                nvdimm_name(nvdimm));
                return -ENOMEM;
@@ -1330,9 +1337,9 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
        nfit_blk->cmd_offset = nfit_mem->dcr->command_offset;
        nfit_blk->stat_offset = nfit_mem->dcr->status_offset;
        mmio = &nfit_blk->mmio[DCR];
-       mmio->base = nfit_spa_map(acpi_desc, nfit_mem->spa_dcr,
+       mmio->addr.base = nfit_spa_map(acpi_desc, nfit_mem->spa_dcr,
                        SPA_MAP_CONTROL);
-       if (!mmio->base) {
+       if (!mmio->addr.base) {
                dev_dbg(dev, "%s: %s failed to map dcr\n", __func__,
                                nvdimm_name(nvdimm));
                return -ENOMEM;
@@ -1399,7 +1406,7 @@ static void acpi_nfit_blk_region_disable(struct nvdimm_bus *nvdimm_bus,
        for (i = 0; i < 2; i++) {
                struct nfit_blk_mmio *mmio = &nfit_blk->mmio[i];
 
-               if (mmio->base)
+               if (mmio->addr.base)
                        nfit_spa_unmap(acpi_desc, mmio->spa);
        }
        nd_blk_region_set_provider_data(ndbr, NULL);

diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
index f2c2bb751882c3b88c39d546441071cbb495eb6f..7e740156b9c2996986e0283e2bdb5d84512929ee 100644 (file)
--- a/drivers/acpi/nfit.h
+++ b/drivers/acpi/nfit.h
@@ -41,6 +41,7 @@ enum nfit_uuids {
 };
 
 enum {
+       ND_BLK_READ_FLUSH = 1,
        ND_BLK_DCR_LATCH = 2,
 };
 
@@ -117,12 +118,16 @@ enum nd_blk_mmio_selector {
        DCR,
 };
 
+struct nd_blk_addr {
+       union {
+               void __iomem *base;
+               void __pmem  *aperture;
+       };
+};
+
 struct nfit_blk {
        struct nfit_blk_mmio {
-               union {
-                       void __iomem *base;
-                       void __pmem  *aperture;
-               };
+               struct nd_blk_addr addr;
                u64 size;
                u64 base_offset;
                u32 line_size;
@@ -149,7 +154,8 @@ struct nfit_spa_mapping {
        struct acpi_nfit_system_address *spa;
        struct list_head list;
        struct kref kref;
-       void __iomem *iomem;
+       enum spa_map_type type;
+       struct nd_blk_addr addr;
 };
 
 static inline struct nfit_spa_mapping *to_spa_map(struct kref *kref)

diff --git a/lib/Kconfig b/lib/Kconfig
index 3a2ef67db6c724f12b6d4ac0550ebb5fd58c5c58..a938a39191b3c5171809e40fd4e56a86f04555e8 100644 (file)
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -531,4 +531,7 @@ config ARCH_HAS_SG_CHAIN
 config ARCH_HAS_PMEM_API
        bool
 
+config ARCH_HAS_MMIO_FLUSH
+       bool
+
 endmenu

diff --git a/tools/testing/nvdimm/Kbuild b/tools/testing/nvdimm/Kbuild
index 04c5fc09576de9b076f38bcaaf2436eab08de7fc..94a5e0eda2d21884517ea96521d56a2c581d4012 100644 (file)
--- a/tools/testing/nvdimm/Kbuild
+++ b/tools/testing/nvdimm/Kbuild
@@ -1,8 +1,10 @@
 ldflags-y += --wrap=ioremap_wc
+ldflags-y += --wrap=memremap
 ldflags-y += --wrap=devm_ioremap_nocache
 ldflags-y += --wrap=devm_memremap
 ldflags-y += --wrap=ioremap_nocache
 ldflags-y += --wrap=iounmap
+ldflags-y += --wrap=memunmap
 ldflags-y += --wrap=__devm_request_region
 ldflags-y += --wrap=__request_region
 ldflags-y += --wrap=__release_region

diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index ff1e0045886409c998c5afb6a6a91d550bd04997..179d2289f3a8289874edccfe6ffcbe8cffd058e4 100644 (file)
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -89,12 +89,25 @@ void *__wrap_devm_memremap(struct device *dev, resource_size_t offset,
        nfit_res = get_nfit_res(offset);
        rcu_read_unlock();
        if (nfit_res)
-               return (void __iomem *) nfit_res->buf + offset
-                       - nfit_res->res->start;
+               return nfit_res->buf + offset - nfit_res->res->start;
        return devm_memremap(dev, offset, size, flags);
 }
 EXPORT_SYMBOL(__wrap_devm_memremap);
 
+void *__wrap_memremap(resource_size_t offset, size_t size,
+               unsigned long flags)
+{
+       struct nfit_test_resource *nfit_res;
+
+       rcu_read_lock();
+       nfit_res = get_nfit_res(offset);
+       rcu_read_unlock();
+       if (nfit_res)
+               return nfit_res->buf + offset - nfit_res->res->start;
+       return memremap(offset, size, flags);
+}
+EXPORT_SYMBOL(__wrap_memremap);
+
 void __iomem *__wrap_ioremap_nocache(resource_size_t offset, unsigned long size)
 {
        return __nfit_test_ioremap(offset, size, ioremap_nocache);
@@ -120,6 +133,19 @@ void __wrap_iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(__wrap_iounmap);
 
+void __wrap_memunmap(void *addr)
+{
+       struct nfit_test_resource *nfit_res;
+
+       rcu_read_lock();
+       nfit_res = get_nfit_res((unsigned long) addr);
+       rcu_read_unlock();
+       if (nfit_res)
+               return;
+       return memunmap(addr);
+}
+EXPORT_SYMBOL(__wrap_memunmap);
+
 static struct resource *nfit_test_request_region(struct device *dev,
                struct resource *parent, resource_size_t start,
                resource_size_t n, const char *name, int flags)

diff --git a/tools/testing/nvdimm/test/nfit.c b/tools/testing/nvdimm/test/nfit.c
index 28dba918524e5bc5d02e8f0b2f87fe514b69beaa..021e6f97f33e7af2a7e570ba46cd29b72523b130 100644 (file)
--- a/tools/testing/nvdimm/test/nfit.c
+++ b/tools/testing/nvdimm/test/nfit.c
@@ -1029,9 +1029,13 @@ static int nfit_test_blk_do_io(struct nd_blk_region *ndbr, resource_size_t dpa,
 
        lane = nd_region_acquire_lane(nd_region);
        if (rw)
-               memcpy(mmio->base + dpa, iobuf, len);
-       else
-               memcpy(iobuf, mmio->base + dpa, len);
+               memcpy(mmio->addr.base + dpa, iobuf, len);
+       else {
+               memcpy(iobuf, mmio->addr.base + dpa, len);
+
+               /* give us some some coverage of the mmio_flush_range() API */
+               mmio_flush_range(mmio->addr.base + dpa, len);
+       }
        nd_region_release_lane(nd_region, lane);
 
        return 0;