From 5fcc48d521877c5d83828d715c81f4d169ef97f3 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 23 Apr 2026 17:56:13 +0200 Subject: [PATCH] x86/kvm/vmx: Fix VMX vs hrtimer_rearm_deferred() Vishal reported that KVM unit test 'x2apic' started failing after commit 0e98eb14814e ("entry: Prepare for deferred hrtimer rearming"). The reason is that KVM/VMX is injecting interrupts while it has interrupts disabled, for a context that will enable interrupts, this means that regs->flags.X86_EFLAGS_IF == 0 and irqentry_exit() will not do the right thing. Notably, irqentry_exit() must not call hrtimer_rearm_deferred() when the return context does not have IF set, because this will cause problems vs NMIs. Therefore, fix up the state after the injection. Fixes: 0e98eb14814e ("entry: Prepare for deferred hrtimer rearming") Reported-by: "Verma, Vishal L" Suggested-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Tested-by: "Verma, Vishal L" Tested-by: David Woodhouse Tested-by: Zhao Liu Tested-by: Sean Christopherson Reviewed-by: Binbin Wu Link: https://patch.msgid.link/20260423155936.957351833@infradead.org Closes: https://lore.kernel.org/r/70cd3e97fbb796e2eb2ff8cd4b7614ada05a5f24.camel%40intel.com --- arch/x86/entry/common.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index b62ac824c1e9..06c7c6ebd6f9 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -2,6 +2,7 @@ #include #include +#include #include #include @@ -27,6 +28,18 @@ noinstr void x86_entry_from_kvm(unsigned int event_type, unsigned int vector) #else idt_entry_from_kvm(vector); #endif + /* + * Strictly speaking, only the NMI path requires noinstr. + */ + instrumentation_begin(); + /* + * KVM/VMX will dispatch from IRQ-disabled but for a context + * that will have IRQs-enabled. This confuses the entry code + * and it will not have reprogrammed the timer. Do so now. + */ + hrtimer_rearm_deferred(); + instrumentation_end(); + return; }