[PATCH v2 6/7] platform/x86/amd/hsmp: Make metric table read locking use guard(mutex)

[Muralidhara M K <muralidhara.mk@amd.com>]

Add a per-socket mutex (metric_tbl_lock) to serialize concurrent
reads on the metric table sysfs file.  Without serialization, two
simultaneous readers could interleave the SMU refresh command and
the memcpy_fromio(), producing a torn (mixed old/new) snapshot.

Use the scoped guard(mutex) API from <linux/cleanup.h> so the lock
is automatically released when hsmp_metric_tbl_read() returns,
including on error paths.

Co-developed-by: Muthusamy Ramalingam <muthusamy.ramalingam@amd.com>
Signed-off-by: Muthusamy Ramalingam <muthusamy.ramalingam@amd.com>
Signed-off-by: Muralidhara M K <muralidhara.mk@amd.com>
---
Changes v1->v2: New patch

 drivers/platform/x86/amd/hsmp/hsmp.c | 5 +++++
 drivers/platform/x86/amd/hsmp/hsmp.h | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/drivers/platform/x86/amd/hsmp/hsmp.c b/drivers/platform/x86/amd/hsmp/hsmp.c
index d6e377078182..49e7ed9981e9 100644
--- a/drivers/platform/x86/amd/hsmp/hsmp.c
+++ b/drivers/platform/x86/amd/hsmp/hsmp.c
@@ -10,7 +10,9 @@
 #include <asm/amd/hsmp.h>
 
 #include <linux/acpi.h>
+#include <linux/cleanup.h>
 #include <linux/delay.h>
+#include <linux/mutex.h>
 #include <linux/device.h>
 #include <linux/semaphore.h>
 #include <linux/sysfs.h>
@@ -364,6 +366,7 @@ ssize_t hsmp_metric_tbl_read(struct hsmp_socket *sock, char *buf, size_t size)
 	msg.msg_id	= HSMP_GET_METRIC_TABLE;
 	msg.sock_ind	= sock->sock_ind;
 
+	guard(mutex)(&sock->metric_tbl_lock);
 	ret = hsmp_send_message(&msg);
 	if (ret)
 		return ret;
@@ -408,6 +411,8 @@ int hsmp_get_tbl_dram_base(u16 sock_ind)
 		dev_err(sock->dev, "Failed to ioremap metric table addr\n");
 		return -ENOMEM;
 	}
+
+	mutex_init(&sock->metric_tbl_lock);
 	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(hsmp_get_tbl_dram_base, "AMD_HSMP");
diff --git a/drivers/platform/x86/amd/hsmp/hsmp.h b/drivers/platform/x86/amd/hsmp/hsmp.h
index e7f051475728..038678b8ab0e 100644
--- a/drivers/platform/x86/amd/hsmp/hsmp.h
+++ b/drivers/platform/x86/amd/hsmp/hsmp.h
@@ -16,6 +16,7 @@
 #include <linux/kconfig.h>
 #include <linux/miscdevice.h>
 #include <linux/pci.h>
+#include <linux/mutex.h>
 #include <linux/semaphore.h>
 #include <linux/sysfs.h>
 
@@ -41,6 +42,8 @@ struct hsmp_socket {
 	struct bin_attribute hsmp_attr;
 	struct hsmp_mbaddr_info mbinfo;
 	void __iomem *metric_tbl_addr;
+	/* Serializes concurrent metric table reads */
+	struct mutex metric_tbl_lock;
 	void __iomem *virt_base_addr;
 	struct semaphore hsmp_sem;
 	char name[HSMP_ATTR_GRP_NAME_SIZE];
-- 
2.34.1