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

[Ilpo Järvinen]

On Mon, 27 Apr 2026, Muralidhara M K wrote:

> 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@xxxxxxx>
> Signed-off-by: Muthusamy Ramalingam <muthusamy.ramalingam@xxxxxxx>
> Signed-off-by: Muralidhara M K <muralidhara.mk@xxxxxxx>
> ---
> 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);

devm_mutex_init() + don't forget to handle errors. (without devm_ you'd 
have to handle mutex_destroy() calls too)

>  	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];
> 

-- 
 i.