From f4e61f0c9add3b00bd5f2df3c814d688849b8707 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Mon, 15 Mar 2021 14:55:28 +0800 Subject: [PATCH] x86/kvm: Fix broken irq restoration in kvm_wait After commit 997acaf6b4b59c (lockdep: report broken irq restoration), the guest splatting below during boot: raw_local_irq_restore() called with IRQs enabled WARNING: CPU: 1 PID: 169 at kernel/locking/irqflag-debug.c:10 warn_bogus_irq_restore+0x26/0x30 Modules linked in: hid_generic usbhid hid CPU: 1 PID: 169 Comm: systemd-udevd Not tainted 5.11.0+ #25 RIP: 0010:warn_bogus_irq_restore+0x26/0x30 Call Trace: kvm_wait+0x76/0x90 __pv_queued_spin_lock_slowpath+0x285/0x2e0 do_raw_spin_lock+0xc9/0xd0 _raw_spin_lock+0x59/0x70 lockref_get_not_dead+0xf/0x50 __legitimize_path+0x31/0x60 legitimize_root+0x37/0x50 try_to_unlazy_next+0x7f/0x1d0 lookup_fast+0xb0/0x170 path_openat+0x165/0x9b0 do_filp_open+0x99/0x110 do_sys_openat2+0x1f1/0x2e0 do_sys_open+0x5c/0x80 __x64_sys_open+0x21/0x30 do_syscall_64+0x32/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xae The new consistency checking, expects local_irq_save() and local_irq_restore() to be paired and sanely nested, and therefore expects local_irq_restore() to be called with irqs disabled. The irqflags handling in kvm_wait() which ends up doing: local_irq_save(flags); safe_halt(); local_irq_restore(flags); instead triggers it. This patch fixes it by using local_irq_disable()/enable() directly. Cc: Thomas Gleixner Reported-by: Dmitry Vyukov Signed-off-by: Wanpeng Li Message-Id: <1615791328-2735-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini --- arch/x86/kernel/kvm.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 5e78e01ca3b4..78bb0fae3982 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -836,28 +836,25 @@ static void kvm_kick_cpu(int cpu) static void kvm_wait(u8 *ptr, u8 val) { - unsigned long flags; - if (in_nmi()) return; - local_irq_save(flags); - - if (READ_ONCE(*ptr) != val) - goto out; - /* * halt until it's our turn and kicked. Note that we do safe halt * for irq enabled case to avoid hang when lock info is overwritten * in irq spinlock slowpath and no spurious interrupt occur to save us. */ - if (arch_irqs_disabled_flags(flags)) - halt(); - else - safe_halt(); + if (irqs_disabled()) { + if (READ_ONCE(*ptr) == val) + halt(); + } else { + local_irq_disable(); -out: - local_irq_restore(flags); + if (READ_ONCE(*ptr) == val) + safe_halt(); + + local_irq_enable(); + } } #ifdef CONFIG_X86_32