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

["M K, Muralidhara" <muralimk@amd.com>]

On 5/11/2026 10:57 PM, Ilpo Järvinen wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> 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@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);
> 
> devm_mutex_init() + don't forget to handle errors. (without devm_ you'd
> have to handle mutex_destroy() calls too)
> 
Thank you for the suggestion. I will update the code and test the changes.
I'll send the next version once I've verified it works properly.

>>        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.
>