This is a note to let you know that I've just added the patch titled
x86/entry: Remove unwanted instrumentation in common_interrupt()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-entry-remove-unwanted-instrumentation-in-common_.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit a58c4b2776f15eb6a28223875969a0960b9874a1
Author: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Date: Tue Jun 11 09:50:30 2024 +0200
x86/entry: Remove unwanted instrumentation in common_interrupt()
[ Upstream commit 477d81a1c47a1b79b9c08fc92b5dea3c5143800b ]
common_interrupt() and related variants call kvm_set_cpu_l1tf_flush_l1d(),
which is neither marked noinstr nor __always_inline.
So compiler puts it out of line and adds instrumentation to it. Since the
call is inside of instrumentation_begin/end(), objtool does not warn about
it.
The manifestation is that KCOV produces spurious coverage in
kvm_set_cpu_l1tf_flush_l1d() in random places because the call happens when
preempt count is not yet updated to say that the kernel is in an interrupt.
Mark kvm_set_cpu_l1tf_flush_l1d() as __always_inline and move it out of the
instrumentation_begin/end() section. It only calls __this_cpu_write()
which is already safe to call in noinstr contexts.
Fixes: 6368558c3710 ("x86/entry: Provide IDTENTRY_SYSVEC")
Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/3f9a1de9e415fcb53d07dc9e19fa8481bb021b1b.1718092070.git.dvyukov@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 275e7fd20310f..a18df4191699c 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -62,7 +62,11 @@ extern u64 arch_irq_stat(void);
#if IS_ENABLED(CONFIG_KVM_INTEL)
-static inline void kvm_set_cpu_l1tf_flush_l1d(void)
+/*
+ * This function is called from noinstr interrupt contexts
+ * and must be inlined to not get instrumentation.
+ */
+static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void)
{
__this_cpu_write(irq_stat.kvm_cpu_l1tf_flush_l1d, 1);
}
@@ -77,7 +81,7 @@ static __always_inline bool kvm_get_cpu_l1tf_flush_l1d(void)
return __this_cpu_read(irq_stat.kvm_cpu_l1tf_flush_l1d);
}
#else /* !IS_ENABLED(CONFIG_KVM_INTEL) */
-static inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
+static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
#endif /* IS_ENABLED(CONFIG_KVM_INTEL) */
#endif /* _ASM_X86_HARDIRQ_H */
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index a65575136255b..151cd0b5f4306 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -210,8 +210,8 @@ __visible noinstr void func(struct pt_regs *regs, \
irqentry_state_t state = irqentry_enter(regs); \
u32 vector = (u32)(u8)error_code; \
\
+ kvm_set_cpu_l1tf_flush_l1d(); \
instrumentation_begin(); \
- kvm_set_cpu_l1tf_flush_l1d(); \
run_irq_on_irqstack_cond(__##func, regs, vector); \
instrumentation_end(); \
irqentry_exit(regs, state); \
@@ -248,7 +248,6 @@ static void __##func(struct pt_regs *regs); \
\
static __always_inline void instr_##func(struct pt_regs *regs) \
{ \
- kvm_set_cpu_l1tf_flush_l1d(); \
run_sysvec_on_irqstack_cond(__##func, regs); \
} \
\
@@ -256,6 +255,7 @@ __visible noinstr void func(struct pt_regs *regs) \
{ \
irqentry_state_t state = irqentry_enter(regs); \
\
+ kvm_set_cpu_l1tf_flush_l1d(); \
instrumentation_begin(); \
instr_##func (regs); \
instrumentation_end(); \
@@ -286,7 +286,6 @@ static __always_inline void __##func(struct pt_regs *regs); \
static __always_inline void instr_##func(struct pt_regs *regs) \
{ \
__irq_enter_raw(); \
- kvm_set_cpu_l1tf_flush_l1d(); \
__##func (regs); \
__irq_exit_raw(); \
} \
@@ -295,6 +294,7 @@ __visible noinstr void func(struct pt_regs *regs) \
{ \
irqentry_state_t state = irqentry_enter(regs); \
\
+ kvm_set_cpu_l1tf_flush_l1d(); \
instrumentation_begin(); \
instr_##func (regs); \
instrumentation_end(); \
