platform/x86: ISST: Do Not Restore SST MSRs on CPU Online Operation

JIRA: https://issues.redhat.com/browse/RHEL-110834

commit c935ddf
Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Date:   Mon May 5 13:27:22 2025 -0700

    platform/x86: ISST: Do Not Restore SST MSRs on CPU Online Operation

    During CPU offline/online operations, the hardware retains MSR settings.
    Even if all CPUs are offlined, the package does not lose its MSR
    settings.

    Therefore, it is unnecessary to restore MSRs which are modified during
    the online operation, and this extra step can be removed.

    Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
    Link: https://lore.kernel.org/r/20250505202722.1048675-1-srinivas.pandruvada@linux.intel.com
    Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
    Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

drivers/platform/x86/intel/speed_select_if/isst_if_common.c

@@ -198,25 +198,6 @@ void isst_resume_common(void)
 }
 EXPORT_SYMBOL_GPL(isst_resume_common);
 
-static void isst_restore_msr_local(int cpu)
-{
-	struct isst_cmd *sst_cmd;
-	int i;
-
-	mutex_lock(&isst_hash_lock);
-	for (i = 0; i < ARRAY_SIZE(punit_msr_white_list); ++i) {
-		if (!punit_msr_white_list[i])
-			break;
-
-		hash_for_each_possible(isst_hash, sst_cmd, hnode,
-				       punit_msr_white_list[i]) {
-			if (!sst_cmd->mbox_cmd_type && sst_cmd->cpu == cpu)
-				wrmsrl_safe(sst_cmd->cmd, sst_cmd->data);
-		}
-	}
-	mutex_unlock(&isst_hash_lock);
-}
-
 /**
  * isst_if_mbox_cmd_invalid() - Check invalid mailbox commands
  * @cmd: Pointer to the command structure to verify.
@@ -434,8 +415,6 @@ static int isst_if_cpu_online(unsigned int cpu)
 set_punit_id:
 	isst_cpu_info[cpu].punit_cpu_id = data;
 
-	isst_restore_msr_local(cpu);
-
 	return 0;
 }