[PATCH v2] nd_blk: add support for "read flush" DSM flag

From: Ross Zwisler
Date: Wed Aug 19 2015 - 18:48:21 EST

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.

By supporting the "read flush" flag we can also change the ND BLK
aperture mapping from write-combining to write-back via memremap().

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@xxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/cacheflush.h | 2 ++
arch/x86/include/asm/io.h | 2 --
arch/x86/include/asm/pmem.h | 2 ++
drivers/acpi/Kconfig | 1 +
drivers/acpi/nfit.c | 55 ++++++++++++++++++++++-----------------
drivers/acpi/nfit.h | 16 ++++++++----
lib/Kconfig | 3 +++
tools/testing/nvdimm/Kbuild | 2 ++
tools/testing/nvdimm/test/iomap.c | 30 +++++++++++++++++++--
tools/testing/nvdimm/test/nfit.c | 10 ++++---
11 files changed, 88 insertions(+), 36 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 76c6115..03ab612 100644
--- 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 471418a..e63aa38 100644
--- 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 d241fbd..83ec9b1 100644
--- 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 a3a0df6..bb026c5 100644
--- 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 114cf48..4baeb85 100644
--- 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 7c2638f..56fff01 100644
--- 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 f2c2bb7..7e74015 100644
--- 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 3a2ef67..a938a39 100644
--- 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 e667579..98f2881 100644
--- 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 ff1e004..179d228 100644
--- 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 28dba91..021e6f9 100644
--- 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;
--
2.1.0

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