The following commit has been merged into the x86/build branch of tip:
Commit-ID: 477d81a1c47a1b79b9c08fc92b5dea3c5143800b Gitweb: https://git.kernel.org/tip/477d81a1c47a1b79b9c08fc92b5dea3c5143800b Author: Dmitry Vyukov dvyukov@google.com AuthorDate: Tue, 11 Jun 2024 09:50:30 +02:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Thu, 08 Aug 2024 17:36:35 +02:00
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 dvyukov@google.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Alexander Potapenko glider@google.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/3f9a1de9e415fcb53d07dc9e19fa8481bb021b1b.1718092...
--- arch/x86/include/asm/hardirq.h | 8 ++++++-- arch/x86/include/asm/idtentry.h | 6 +++--- 2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h index c67fa6a..6ffa8b7 100644 --- a/arch/x86/include/asm/hardirq.h +++ b/arch/x86/include/asm/hardirq.h @@ -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 */ diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index d4f2449..ad5c68f 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -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(); \