[PATCH 6.12 105/567] ACPI: CPPC: Fix missing PCC check for guaranteed_perf

Greg Kroah-Hartman
2026-01-06T17:21:51Z

From: Pengjie Zhang <zhangpengjie2@huawei.com>

commit 6ea3a44cef28add2d93b1ef119d84886cb1e3c9b upstream.

The current implementation overlooks the 'guaranteed_perf'
register in this check.

If the Guaranteed Performance register is located in the PCC
subspace, the function currently attempts to read it without
acquiring the lock and without sending the CMD_READ doorbell
to the firmware. This can result in reading stale data.

Fixes: 29523f095397 ("ACPI / CPPC: Add support for guaranteed performance")
Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
Cc: 4.20+ <stable@vger.kernel.org> # 4.20+
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20251210132227.1988380-1-zhangpengjie2@huawei.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/acpi/cppc_acpi.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1297,7 +1297,8 @@ int cppc_get_perf_caps(int cpunum, struc
/* Are any of the regs PCC ?*/
if (CPC_IN_PCC(highest_reg) || CPC_IN_PCC(lowest_reg) ||
CPC_IN_PCC(lowest_non_linear_reg) || CPC_IN_PCC(nominal_reg) ||
- CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg)) {
+ CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg) ||
+ CPC_IN_PCC(guaranteed_reg)) {
if (pcc_ss_id < 0) {
pr_debug("Invalid pcc_ss_id\n");
return -ENODEV;