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

[M K, Muralidhara]

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@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)
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.