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Date: Tue, 18 Aug 2015 11:14:46 -0600
From: Ross Zwisler <ross.zwisler@...ux.intel.com>
To: linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
Dan Williams <dan.j.williams@...el.com>,
Christoph Hellwig <hch@....de>,
Matthew Wilcox <matthew.r.wilcox@...el.com>,
Dave Chinner <david@...morbit.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Subject: [PATCH v4 5/7] pmem: add copy_from_iter_pmem() and clear_pmem()
Add support for two new PMEM APIs, copy_from_iter_pmem() and
clear_pmem(). copy_from_iter_pmem() is used to copy data from an
iterator into a PMEM buffer. clear_pmem() zeros a PMEM memory range.
Both of these new APIs must be explicitly ordered using a wmb_pmem()
function call and are implemented in such a way that the wmb_pmem()
will make the stores to PMEM durable. Because both APIs are unordered
they can be called as needed without introducing any unwanted memory
barriers.
Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
arch/x86/include/asm/pmem.h | 75 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/pmem.h | 66 +++++++++++++++++++++++++++++++++++++--
2 files changed, 138 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
index 7f3413f..a3a0df6 100644
--- a/arch/x86/include/asm/pmem.h
+++ b/arch/x86/include/asm/pmem.h
@@ -66,6 +66,81 @@ static inline void arch_wmb_pmem(void)
pcommit_sfence();
}
+/**
+ * __arch_wb_cache_pmem - write back a cache range with CLWB
+ * @vaddr: virtual start address
+ * @size: number of bytes to write back
+ *
+ * Write back a cache range using the CLWB (cache line write back)
+ * instruction. This function requires explicit ordering with an
+ * arch_wmb_pmem() call. This API is internal to the x86 PMEM implementation.
+ */
+static inline void __arch_wb_cache_pmem(void *vaddr, size_t size)
+{
+ u16 x86_clflush_size = boot_cpu_data.x86_clflush_size;
+ unsigned long clflush_mask = x86_clflush_size - 1;
+ void *vend = vaddr + size;
+ void *p;
+
+ for (p = (void *)((unsigned long)vaddr & ~clflush_mask);
+ p < vend; p += x86_clflush_size)
+ clwb(p);
+}
+
+/*
+ * copy_from_iter_nocache() on x86 only uses non-temporal stores for iovec
+ * iterators, so for other types (bvec & kvec) we must do a cache write-back.
+ */
+static inline bool __iter_needs_pmem_wb(struct iov_iter *i)
+{
+ return iter_is_iovec(i) == false;
+}
+
+/**
+ * arch_copy_from_iter_pmem - copy data from an iterator to PMEM
+ * @addr: PMEM destination address
+ * @bytes: number of bytes to copy
+ * @i: iterator with source data
+ *
+ * Copy data from the iterator 'i' to the PMEM buffer starting at 'addr'.
+ * This function requires explicit ordering with an arch_wmb_pmem() call.
+ */
+static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ void *vaddr = (void __force *)addr;
+ size_t len;
+
+ /* TODO: skip the write-back by always using non-temporal stores */
+ len = copy_from_iter_nocache(vaddr, bytes, i);
+
+ if (__iter_needs_pmem_wb(i))
+ __arch_wb_cache_pmem(vaddr, bytes);
+
+ return len;
+}
+
+/**
+ * arch_clear_pmem - zero a PMEM memory range
+ * @addr: virtual start address
+ * @size: number of bytes to zero
+ *
+ * Write zeros into the memory range starting at 'addr' for 'size' bytes.
+ * This function requires explicit ordering with an arch_wmb_pmem() call.
+ */
+static inline void arch_clear_pmem(void __pmem *addr, size_t size)
+{
+ void *vaddr = (void __force *)addr;
+
+ /* TODO: implement the zeroing via non-temporal writes */
+ if (size == PAGE_SIZE && ((unsigned long)vaddr & ~PAGE_MASK) == 0)
+ clear_page(vaddr);
+ else
+ memset(vaddr, 0, size);
+
+ __arch_wb_cache_pmem(vaddr, size);
+}
+
static inline bool arch_has_wmb_pmem(void)
{
#ifdef CONFIG_X86_64
diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index 9d619d2..c7f57eb 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -14,6 +14,7 @@
#define __PMEM_H__
#include <linux/io.h>
+#include <linux/uio.h>
#ifdef CONFIG_ARCH_HAS_PMEM_API
#include <asm/pmem.h>
@@ -39,12 +40,24 @@ static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
{
BUG();
}
+
+static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ BUG();
+ return 0;
+}
+
+static inline void arch_clear_pmem(void __pmem *addr, size_t size)
+{
+ BUG();
+}
#endif
/*
- * Architectures that define ARCH_HAS_PMEM_API must provide
- * implementations for arch_memremap_pmem(), arch_memcpy_to_pmem(),
- * arch_wmb_pmem(), and arch_has_wmb_pmem().
+ * Architectures that define ARCH_HAS_PMEM_API must provide implementations
+ * for arch_memremap_pmem(), arch_memcpy_to_pmem(), arch_wmb_pmem(),
+ * arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem().
*/
static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size)
@@ -90,6 +103,20 @@ static void __pmem *default_memremap_pmem(resource_size_t offset,
return (void __pmem __force *)ioremap_wt(offset, size);
}
+static inline size_t default_copy_from_iter_pmem(void __pmem *addr,
+ size_t bytes, struct iov_iter *i)
+{
+ return copy_from_iter_nocache((void __force *)addr, bytes, i);
+}
+
+static inline void default_clear_pmem(void __pmem *addr, size_t size)
+{
+ if (size == PAGE_SIZE && ((unsigned long)addr & ~PAGE_MASK) == 0)
+ clear_page((void __force *)addr);
+ else
+ memset((void __force *)addr, 0, size);
+}
+
/**
* memremap_pmem - map physical persistent memory for pmem api
* @offset: physical address of persistent memory
@@ -142,4 +169,37 @@ static inline void wmb_pmem(void)
if (arch_has_pmem_api())
arch_wmb_pmem();
}
+
+/**
+ * copy_from_iter_pmem - copy data from an iterator to PMEM
+ * @addr: PMEM destination address
+ * @bytes: number of bytes to copy
+ * @i: iterator with source data
+ *
+ * Copy data from the iterator 'i' to the PMEM buffer starting at 'addr'.
+ * This function requires explicit ordering with a wmb_pmem() call.
+ */
+static inline size_t copy_from_iter_pmem(void __pmem *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ if (arch_has_pmem_api())
+ return arch_copy_from_iter_pmem(addr, bytes, i);
+ return default_copy_from_iter_pmem(addr, bytes, i);
+}
+
+/**
+ * clear_pmem - zero a PMEM memory range
+ * @addr: virtual start address
+ * @size: number of bytes to zero
+ *
+ * Write zeros into the memory range starting at 'addr' for 'size' bytes.
+ * This function requires explicit ordering with a wmb_pmem() call.
+ */
+static inline void clear_pmem(void __pmem *addr, size_t size)
+{
+ if (arch_has_pmem_api())
+ arch_clear_pmem(addr, size);
+ else
+ default_clear_pmem(addr, size);
+}
#endif /* __PMEM_H__ */
--
2.1.0
--
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