6.6-stable review patch. If anyone has any objections, please let me know.
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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 @@ -1299,7 +1299,8 @@ 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;