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Message-ID: <20130424072630.GB1780@gmail.com>
Date: Wed, 24 Apr 2013 09:26:30 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Cyrill Gorcunov <gorcunov@...il.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
David Miller <davem@...emloft.net>,
Theodore Ts'o <tytso@....edu>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>,
Network Development <netdev@...r.kernel.org>,
"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
Oleg Nesterov <oleg@...hat.com>,
Fr??d??ric Weisbecker <fweisbec@...il.com>
Subject: Re: Unsigned widening casts of binary "not" operations..
* Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> And there's quite a lot of them. Even in my (fairly small) config I use on
> my desktop. And the first warnings I see are in x86 code:
>
> arch/x86/kernel/traps.c:405:16: warning: implicit unsigned widening
> cast of a '~' expression
> arch/x86/kernel/cpu/perf_event_p4.c:912:15: warning: implicit unsigned
> widening cast of a '~' expression
Hm, the perf_event_p4.c code is indeed confused.
I think the bug is real but probably benign in effect: we allow narrower
values into the MSR register than probably intended. Only a couple of low
bits are reserved AFAICS.
Here's an (untested!) patch that tries to untangle it all: it just moves
to clean 64-bit types everywhere - these MSRs are 64-bit wide regardless
of whether we run on 32-bit or not.
Would be nice if someone with a working P4 could test it - Cyrill? [It
should also be double checked whether the high words are really not
reserved and can be written to ...]
Thanks,
Ingo
---->
Linus, while extending integer type extension checks in the sparse static
code checker, found fragile patterns of mixed signed/unsigned
64-bit/32-bit integer use in perf_events_p4.c.
The relevant hardware register ABI is 64 bit wide on 32-bit kernels as
well, so clean it all up a bit, remove unnecessary casts, and make sure we
use 64-bit unsigned integers in these places.
Signed-off-by: Ingo Molnar <mingo@...nel.org>
diff --git a/arch/x86/include/asm/perf_event_p4.h b/arch/x86/include/asm/perf_event_p4.h
index 4f7e67e..85e13cc 100644
--- a/arch/x86/include/asm/perf_event_p4.h
+++ b/arch/x86/include/asm/perf_event_p4.h
@@ -24,45 +24,45 @@
#define ARCH_P4_CNTRVAL_MASK ((1ULL << ARCH_P4_CNTRVAL_BITS) - 1)
#define ARCH_P4_UNFLAGGED_BIT ((1ULL) << (ARCH_P4_CNTRVAL_BITS - 1))
-#define P4_ESCR_EVENT_MASK 0x7e000000U
+#define P4_ESCR_EVENT_MASK 0x7e000000ULL
#define P4_ESCR_EVENT_SHIFT 25
-#define P4_ESCR_EVENTMASK_MASK 0x01fffe00U
+#define P4_ESCR_EVENTMASK_MASK 0x01fffe00ULL
#define P4_ESCR_EVENTMASK_SHIFT 9
-#define P4_ESCR_TAG_MASK 0x000001e0U
+#define P4_ESCR_TAG_MASK 0x000001e0ULL
#define P4_ESCR_TAG_SHIFT 5
-#define P4_ESCR_TAG_ENABLE 0x00000010U
-#define P4_ESCR_T0_OS 0x00000008U
-#define P4_ESCR_T0_USR 0x00000004U
-#define P4_ESCR_T1_OS 0x00000002U
-#define P4_ESCR_T1_USR 0x00000001U
+#define P4_ESCR_TAG_ENABLE 0x00000010ULL
+#define P4_ESCR_T0_OS 0x00000008ULL
+#define P4_ESCR_T0_USR 0x00000004ULL
+#define P4_ESCR_T1_OS 0x00000002ULL
+#define P4_ESCR_T1_USR 0x00000001ULL
#define P4_ESCR_EVENT(v) ((v) << P4_ESCR_EVENT_SHIFT)
#define P4_ESCR_EMASK(v) ((v) << P4_ESCR_EVENTMASK_SHIFT)
#define P4_ESCR_TAG(v) ((v) << P4_ESCR_TAG_SHIFT)
-#define P4_CCCR_OVF 0x80000000U
-#define P4_CCCR_CASCADE 0x40000000U
-#define P4_CCCR_OVF_PMI_T0 0x04000000U
-#define P4_CCCR_OVF_PMI_T1 0x08000000U
-#define P4_CCCR_FORCE_OVF 0x02000000U
-#define P4_CCCR_EDGE 0x01000000U
-#define P4_CCCR_THRESHOLD_MASK 0x00f00000U
+#define P4_CCCR_OVF 0x80000000ULL
+#define P4_CCCR_CASCADE 0x40000000ULL
+#define P4_CCCR_OVF_PMI_T0 0x04000000ULL
+#define P4_CCCR_OVF_PMI_T1 0x08000000ULL
+#define P4_CCCR_FORCE_OVF 0x02000000ULL
+#define P4_CCCR_EDGE 0x01000000ULL
+#define P4_CCCR_THRESHOLD_MASK 0x00f00000ULL
#define P4_CCCR_THRESHOLD_SHIFT 20
-#define P4_CCCR_COMPLEMENT 0x00080000U
-#define P4_CCCR_COMPARE 0x00040000U
-#define P4_CCCR_ESCR_SELECT_MASK 0x0000e000U
+#define P4_CCCR_COMPLEMENT 0x00080000ULL
+#define P4_CCCR_COMPARE 0x00040000ULL
+#define P4_CCCR_ESCR_SELECT_MASK 0x0000e000ULL
#define P4_CCCR_ESCR_SELECT_SHIFT 13
-#define P4_CCCR_ENABLE 0x00001000U
-#define P4_CCCR_THREAD_SINGLE 0x00010000U
-#define P4_CCCR_THREAD_BOTH 0x00020000U
-#define P4_CCCR_THREAD_ANY 0x00030000U
-#define P4_CCCR_RESERVED 0x00000fffU
+#define P4_CCCR_ENABLE 0x00001000ULL
+#define P4_CCCR_THREAD_SINGLE 0x00010000ULL
+#define P4_CCCR_THREAD_BOTH 0x00020000ULL
+#define P4_CCCR_THREAD_ANY 0x00030000ULL
+#define P4_CCCR_RESERVED 0x00000fffULL
#define P4_CCCR_THRESHOLD(v) ((v) << P4_CCCR_THRESHOLD_SHIFT)
#define P4_CCCR_ESEL(v) ((v) << P4_CCCR_ESCR_SELECT_SHIFT)
#define P4_GEN_ESCR_EMASK(class, name, bit) \
- class##__##name = ((1 << bit) << P4_ESCR_EVENTMASK_SHIFT)
+ class##__##name = ((1ULL << bit) << P4_ESCR_EVENTMASK_SHIFT)
#define P4_ESCR_EMASK_BIT(class, name) class##__##name
/*
@@ -107,7 +107,7 @@
* P4_PEBS_CONFIG_MASK and related bits on
* modification.)
*/
-#define P4_CONFIG_ALIASABLE (1 << 9)
+#define P4_CONFIG_ALIASABLE (1ULL << 9)
/*
* The bits we allow to pass for RAW events
@@ -784,17 +784,17 @@ enum P4_ESCR_EMASKS {
* Note we have UOP and PEBS bits reserved for now
* just in case if we will need them once
*/
-#define P4_PEBS_CONFIG_ENABLE (1 << 7)
-#define P4_PEBS_CONFIG_UOP_TAG (1 << 8)
-#define P4_PEBS_CONFIG_METRIC_MASK 0x3f
-#define P4_PEBS_CONFIG_MASK 0xff
+#define P4_PEBS_CONFIG_ENABLE (1ULL << 7)
+#define P4_PEBS_CONFIG_UOP_TAG (1ULL << 8)
+#define P4_PEBS_CONFIG_METRIC_MASK 0x3FLL
+#define P4_PEBS_CONFIG_MASK 0xFFLL
/*
* mem: Only counters MSR_IQ_COUNTER4 (16) and
* MSR_IQ_COUNTER5 (17) are allowed for PEBS sampling
*/
-#define P4_PEBS_ENABLE 0x02000000U
-#define P4_PEBS_ENABLE_UOP_TAG 0x01000000U
+#define P4_PEBS_ENABLE 0x02000000ULL
+#define P4_PEBS_ENABLE_UOP_TAG 0x01000000ULL
#define p4_config_unpack_metric(v) (((u64)(v)) & P4_PEBS_CONFIG_METRIC_MASK)
#define p4_config_unpack_pebs(v) (((u64)(v)) & P4_PEBS_CONFIG_MASK)
diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index 92c7e39..3486e66 100644
--- a/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/arch/x86/kernel/cpu/perf_event_p4.c
@@ -895,8 +895,8 @@ static void p4_pmu_disable_pebs(void)
* So at moment let leave metrics turned on forever -- it's
* ok for now but need to be revisited!
*
- * (void)wrmsrl_safe(MSR_IA32_PEBS_ENABLE, (u64)0);
- * (void)wrmsrl_safe(MSR_P4_PEBS_MATRIX_VERT, (u64)0);
+ * (void)wrmsrl_safe(MSR_IA32_PEBS_ENABLE, 0);
+ * (void)wrmsrl_safe(MSR_P4_PEBS_MATRIX_VERT, 0);
*/
}
@@ -910,8 +910,7 @@ static inline void p4_pmu_disable_event(struct perf_event *event)
* asserted again and again
*/
(void)wrmsrl_safe(hwc->config_base,
- (u64)(p4_config_unpack_cccr(hwc->config)) &
- ~P4_CCCR_ENABLE & ~P4_CCCR_OVF & ~P4_CCCR_RESERVED);
+ p4_config_unpack_cccr(hwc->config) & ~P4_CCCR_ENABLE & ~P4_CCCR_OVF & ~P4_CCCR_RESERVED);
}
static void p4_pmu_disable_all(void)
@@ -957,7 +956,7 @@ static void p4_pmu_enable_event(struct perf_event *event)
u64 escr_addr, cccr;
bind = &p4_event_bind_map[idx];
- escr_addr = (u64)bind->escr_msr[thread];
+ escr_addr = bind->escr_msr[thread];
/*
* - we dont support cascaded counters yet
--
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