readq/writeq: Add explicit lo_hi_[read|write]_q and hi_lo_[read|write]_q

Even on x86-64, I've found the need to break up a readq() into 2 readl()
calls. According to the Intel datasheet for the E3-1200 processor:

"
Software must not access B0/D0/F0 32-bit memory-mapped registers with
requests that cross a DW boundary.
"

(http://www.intel.com/content/www/us/en/processors/xeon/xeon-e3-1200-family-vol-2-datasheet.html p. 16)

I can confirm this is true via several hard machine lockups.

Thus, add explicit hi_lo_[readq|write]_q and lo_hi_[read|write]_q so that these
uses are spelled out.

Signed-off-by: Jason Baron <jbaron@akamai.com>
Link: http://lkml.kernel.org/r/281f09da7ad01e5cea99737ec34d2399bdbbbf63.1403818526.git.jbaron@akamai.com
Signed-off-by: Borislav Petkov <bp@suse.de>

2 files changed, 18 insertions, 10 deletions

diff --git a/include/asm-generic/io-64-nonatomic-hi-lo.h b/include/asm-generic/io-64-nonatomic-hi-lo.h
index a6806a94250d..2e29d13fc154 100644
--- a/include/asm-generic/io-64-nonatomic-hi-lo.h
+++ b/include/asm-generic/io-64-nonatomic-hi-lo.h
@@ -4,8 +4,7 @@
 #include <linux/io.h>
 #include <asm-generic/int-ll64.h>
 
-#ifndef readq
-static inline __u64 readq(const volatile void __iomem *addr)
+static inline __u64 hi_lo_readq(const volatile void __iomem *addr)
 {
         const volatile u32 __iomem *p = addr;
         u32 low, high;
@@ -15,14 +14,19 @@ static inline __u64 readq(const volatile void __iomem *addr)
 
         return low + ((u64)high << 32);
 }
-#endif
 
-#ifndef writeq
-static inline void writeq(__u64 val, volatile void __iomem *addr)
+static inline void hi_lo_writeq(__u64 val, volatile void __iomem *addr)
 {
         writel(val >> 32, addr + 4);
         writel(val, addr);
 }
+
+#ifndef readq
+#define readq hi_lo_readq
+#endif
+
+#ifndef writeq
+#define writeq hi_lo_writeq
 #endif
 
 #endif  /* _ASM_IO_64_NONATOMIC_HI_LO_H_ */
diff --git a/include/asm-generic/io-64-nonatomic-lo-hi.h b/include/asm-generic/io-64-nonatomic-lo-hi.h
index ca546b1ff8b5..0efacff0a1ce 100644
--- a/include/asm-generic/io-64-nonatomic-lo-hi.h
+++ b/include/asm-generic/io-64-nonatomic-lo-hi.h
@@ -4,8 +4,7 @@
 #include <linux/io.h>
 #include <asm-generic/int-ll64.h>
 
-#ifndef readq
-static inline __u64 readq(const volatile void __iomem *addr)
+static inline __u64 lo_hi_readq(const volatile void __iomem *addr)
 {
         const volatile u32 __iomem *p = addr;
         u32 low, high;
@@ -15,14 +14,19 @@ static inline __u64 readq(const volatile void __iomem *addr)
 
         return low + ((u64)high << 32);
 }
-#endif
 
-#ifndef writeq
-static inline void writeq(__u64 val, volatile void __iomem *addr)
+static inline void lo_hi_writeq(__u64 val, volatile void __iomem *addr)
 {
         writel(val, addr);
         writel(val >> 32, addr + 4);
 }
+
+#ifndef readq
+#define readq lo_hi_readq
+#endif
+
+#ifndef writeq
+#define writeq lo_hi_writeq
 #endif
 
 #endif  /* _ASM_IO_64_NONATOMIC_LO_HI_H_ */