[PATCH 6.18 100/309] platform/x86: ISST: Check HWP support before MSR access

Greg Kroah-Hartman
2026-03-31T17:02:24Z

From: Li RongQing <lirongqing@baidu.com>

[ Upstream commit 9f11d9b15efb5f77e810b6dfbeb01b4650a79eae ]

On some systems, HWP can be explicitly disabled in the BIOS settings
When HWP is disabled by firmware, the HWP CPUID bit is not set, and
attempting to read MSR_PM_ENABLE will result in a General Protection
(GP) fault.

unchecked MSR access error: RDMSR from 0x770 at rIP: 0xffffffffc33db92e (disable_dynamic_sst_features+0xe/0x50 [isst_tpmi_core])
Call Trace:
<TASK>
? ex_handler_msr+0xf6/0x150
? fixup_exception+0x1ad/0x340
? gp_try_fixup_and_notify+0x1e/0xb0
? exc_general_protection+0xc9/0x390
? terminate_walk+0x64/0x100
? asm_exc_general_protection+0x22/0x30
? disable_dynamic_sst_features+0xe/0x50 [isst_tpmi_core]
isst_if_def_ioctl+0xece/0x1050 [isst_tpmi_core]
? ioctl_has_perm.constprop.42+0xe0/0x130
isst_if_def_ioctl+0x10d/0x1a0 [isst_if_common]
__se_sys_ioctl+0x86/0xc0
do_syscall_64+0x8a/0x100
entry_SYSCALL_64_after_hwframe+0x78/0xe2
RIP: 0033:0x7f36eaef54a7

Add a check for X86_FEATURE_HWP before accessing the MSR. If HWP is
not available, return true safely.

Fixes: 12a7d2cb811d ("platform/x86: ISST: Add SST-CP support via TPMI")
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/20260303074635.2218-1-lirongqing@baidu.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
index 13b11c3a2ec4e..e657b88bfd36e 100644
--- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
+++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
@@ -558,6 +558,9 @@ static bool disable_dynamic_sst_features(void)
{
u64 value;

+ if (!static_cpu_has(X86_FEATURE_HWP))
+ return true;
+
rdmsrq(MSR_PM_ENABLE, value);
return !(value & 0x1);
}
--
2.51.0