From: Jarred White <jarredwhite@linux.microsoft.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>,
Len Brown <lenb@kernel.org>,
Jarred White <jarredwhite@linux.microsoft.com>,
Easwar Hariharan <eahariha@linux.microsoft.com>,
linux-acpi@vger.kernel.org (open list:ACPI),
linux-kernel@vger.kernel.org (open list)
Cc: Vanshidhar Konda <vanshikonda@os.amperecomputing.com>,
stable@vger.kernel.org
Subject: [PATCH] ACPI: CPPC: Fix bit_offset shift in MASK_VAL macro
Date: Mon, 8 Apr 2024 22:23:09 -0700 [thread overview]
Message-ID: <20240409052310.3162495-1-jarredwhite@linux.microsoft.com> (raw)
Commit 2f4a4d63a193 ("ACPI: CPPC: Use access_width over bit_width for
system memory accesses") neglected to properly wrap the bit_offset shift
when it comes to applying the mask. This may cause incorrect values to be
read and may cause the cpufreq module not be loaded.
[ 11.059751] cpu_capacity: CPU0 missing/invalid highest performance.
[ 11.066005] cpu_capacity: partial information: fallback to 1024 for all CPUs
Also, corrected the bitmask generation in GENMASK (extra bit being added).
Fixes: 2f4a4d63a193 ("ACPI: CPPC: Use access_width over bit_width for system memory accesses")
Signed-off-by: Jarred White <jarredwhite@linux.microsoft.com>
CC: Vanshidhar Konda <vanshikonda@os.amperecomputing.com>
CC: stable@vger.kernel.org #5.15+
---
drivers/acpi/cppc_acpi.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 4bfbe55553f4..00a30ca35e78 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -170,8 +170,8 @@ show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);
#define GET_BIT_WIDTH(reg) ((reg)->access_width ? (8 << ((reg)->access_width - 1)) : (reg)->bit_width)
/* Shift and apply the mask for CPC reads/writes */
-#define MASK_VAL(reg, val) ((val) >> ((reg)->bit_offset & \
- GENMASK(((reg)->bit_width), 0)))
+#define MASK_VAL(reg, val) (((val) >> (reg)->bit_offset) & \
+ GENMASK(((reg)->bit_width) - 1, 0))
static ssize_t show_feedback_ctrs(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
--
2.33.8
next reply other threads:[~2024-04-09 5:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 5:23 Jarred White [this message]
2024-04-16 17:24 ` [PATCH] ACPI: CPPC: Fix bit_offset shift in MASK_VAL macro Jarred White
2024-04-17 17:36 ` Vanshidhar Konda
2024-04-22 16:43 ` Rafael J. Wysocki
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