From 33e60ff64a043b189d2661543b417b21b6f3667b Mon Sep 17 00:00:00 2001

From: Adam Judge <ajudge@iol.unh.edu>

Date: Tue, 9 Jun 2020 15:58:49 -0400

Subject: [PATCH] Prevent compiler from optimizing mmio_read64 to single 64b

 read

---

 nvme-print.c | 8 ++++++--

 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/nvme-print.c b/nvme-print.c

index fc8f99d..c0de928 100644

--- a/nvme-print.c

+++ b/nvme-print.c

@@ -1311,9 +1311,13 @@ static inline uint32_t mmio_read32(void *addr)

 /* Access 64-bit registers as 2 32-bit; Some devices fail 64-bit MMIO. */

 static inline __u64 mmio_read64(void *addr)

 {

-	__le32 *p = addr;

+	const volatile __u32 *p = addr;

+	__u32 low, high;

+

+	low = le32_to_cpu(*p);

+	high = le32_to_cpu(*(p + 1));

-	return le32_to_cpu(*p) | ((uint64_t)le32_to_cpu(*(p + 1)) << 32);

+	return ((__u64) high << 32) | low;

 }

 static void json_ctrl_registers(void *bar)

-- 

2.31.1