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FAILED: patch "[PATCH] x86/entry: Remove unwanted instrumentation in" failed to apply to 6.6-stable tree

PATCH [email protected] 1 participant 1 message Oct 1, 2024

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The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 477d81a1c47a1b79b9c08fc92b5dea3c5143800b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024100136-phrase-smashing-4e41@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

477d81a1c47a ("x86/entry: Remove unwanted instrumentation in common_interrupt()") 90f357208200 ("x86/idtentry: Incorporate definitions/declarations of the FRED entries")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 477d81a1c47a1b79b9c08fc92b5dea3c5143800b Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <[email protected]>
Date: Tue, 11 Jun 2024 09:50:30 +0200
Subject: [PATCH] x86/entry: Remove unwanted instrumentation in
common_interrupt()

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 <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Reviewed-by Alexander Potapenko <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Cc [email protected]
Link https://lore.kernel.org/all/3f9a1de9e415fcb53d07dc9e19fa8481bb021b1b.1718092070.git.dvyukov@google.com open here
arch/x86/include/asm/hardirq.h +6 -2
index c67fa6ad098a..6ffa8b75f4cd 100644
@@ -69,7 +69,11 @@ extern u64 arch_irq_stat(void);
 #define local_softirq_pending_ref       pcpu_hot.softirq_pending
 
 #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);
 }

@@ -84,7 +88,7 @@ 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 */
arch/x86/include/asm/idtentry.h +3 -3
index d4f24499b256..ad5c68f0509d 100644
@@ -212,8 +212,8 @@ __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);					\

@@ -250,7 +250,6 @@ 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);			\
 }									\
 									\

@@ -258,6 +257,7 @@ __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();						\

@@ -288,7 +288,6 @@ 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();						\
 }									\

@@ -297,6 +296,7 @@ __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();						\