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From: Ilya Leoshkevich <iii@linux.ibm.com>
To: Alexander Gordeev <agordeev@linux.ibm.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>, David Rientjes <rientjes@google.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, Marco Elver <elver@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>, Vlastimil Babka <vbabka@suse.cz>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Sven Schnelle <svens@linux.ibm.com>,
        Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH v4 28/35] s390/irqflags: Do not instrument arch_local_irq_*() with KMSAN
Date: Thu, 13 Jun 2024 17:34:30 +0200
Message-ID: <20240613153924.961511-29-iii@linux.ibm.com>
In-Reply-To: <20240613153924.961511-1-iii@linux.ibm.com>
References: <20240613153924.961511-1-iii@linux.ibm.com>
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Lockdep generates the following false positives with KMSAN on s390x:

[    6.063666] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
[         ...]
[    6.577050] Call Trace:
[    6.619637]  [<000000000690d2de>] check_flags+0x1fe/0x210
[    6.665411] ([<000000000690d2da>] check_flags+0x1fa/0x210)
[    6.707478]  [<00000000006cec1a>] lock_acquire+0x2ca/0xce0
[    6.749959]  [<00000000069820ea>] _raw_spin_lock_irqsave+0xea/0x190
[    6.794912]  [<00000000041fc988>] __stack_depot_save+0x218/0x5b0
[    6.838420]  [<000000000197affe>] __msan_poison_alloca+0xfe/0x1a0
[    6.882985]  [<0000000007c5827c>] start_kernel+0x70c/0xd50
[    6.927454]  [<0000000000100036>] startup_continue+0x36/0x40

Between trace_hardirqs_on() and `stosm __mask, 3` lockdep thinks that
interrupts are on, but on the CPU they are still off. KMSAN
instrumentation takes spinlocks, giving lockdep a chance to see and
complain about this discrepancy.

KMSAN instrumentation is inserted in order to poison the __mask
variable. Disable instrumentation in the respective functions. They are
very small and it's easy to see that no important metadata updates are
lost because of this.

Reviewed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/include/asm/irqflags.h | 17 ++++++++++++++---
 drivers/s390/char/sclp.c         |  2 +-
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/s390/include/asm/irqflags.h b/arch/s390/include/asm/irqflags.h
index 02427b205c11..bcab456dfb80 100644
--- a/arch/s390/include/asm/irqflags.h
+++ b/arch/s390/include/asm/irqflags.h
@@ -37,12 +37,18 @@ static __always_inline void __arch_local_irq_ssm(unsigned long flags)
 	asm volatile("ssm   %0" : : "Q" (flags) : "memory");
 }
 
-static __always_inline unsigned long arch_local_save_flags(void)
+#ifdef CONFIG_KMSAN
+#define arch_local_irq_attributes noinline notrace __no_sanitize_memory __maybe_unused
+#else
+#define arch_local_irq_attributes __always_inline
+#endif
+
+static arch_local_irq_attributes unsigned long arch_local_save_flags(void)
 {
 	return __arch_local_irq_stnsm(0xff);
 }
 
-static __always_inline unsigned long arch_local_irq_save(void)
+static arch_local_irq_attributes unsigned long arch_local_irq_save(void)
 {
 	return __arch_local_irq_stnsm(0xfc);
 }
@@ -52,7 +58,12 @@ static __always_inline void arch_local_irq_disable(void)
 	arch_local_irq_save();
 }
 
-static __always_inline void arch_local_irq_enable(void)
+static arch_local_irq_attributes void arch_local_irq_enable_external(void)
+{
+	__arch_local_irq_stosm(0x01);
+}
+
+static arch_local_irq_attributes void arch_local_irq_enable(void)
 {
 	__arch_local_irq_stosm(0x03);
 }
diff --git a/drivers/s390/char/sclp.c b/drivers/s390/char/sclp.c
index d53ee34d398f..fb1d9949adca 100644
--- a/drivers/s390/char/sclp.c
+++ b/drivers/s390/char/sclp.c
@@ -736,7 +736,7 @@ sclp_sync_wait(void)
 	cr0_sync.val = cr0.val & ~CR0_IRQ_SUBCLASS_MASK;
 	cr0_sync.val |= 1UL << (63 - 54);
 	local_ctl_load(0, &cr0_sync);
-	__arch_local_irq_stosm(0x01);
+	arch_local_irq_enable_external();
 	/* Loop until driver state indicates finished request */
 	while (sclp_running_state != sclp_running_state_idle) {
 		/* Check for expired request timer */
-- 
2.45.1