On 11/03/21 16:54, Sean Christopherson wrote:
On Tue, Feb 23, 2021, Wanpeng Li wrote:
On Tue, 23 Feb 2021 at 13:25, Wanpeng Li <kernellwp@xxxxxxxxx> wrote:
From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
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 irqflags handling in kvm_wait() which ends up doing:
local_irq_save(flags);
safe_halt();
local_irq_restore(flags);
which triggered a new consistency checking, we generally expect
local_irq_save() and local_irq_restore() to be pared and sanely
nested, and so local_irq_restore() expects to be called with
irqs disabled.
This patch fixes it by adding a local_irq_disable() after safe_halt()
to avoid this warning.
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kernel/kvm.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 5e78e01..688c84a 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -853,8 +853,10 @@ static void kvm_wait(u8 *ptr, u8 val)
*/
if (arch_irqs_disabled_flags(flags))
halt();
- else
+ else {
safe_halt();
+ local_irq_disable();
+ }
An alternative fix:
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 5e78e01..7127aef 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -836,12 +836,13 @@ static void kvm_kick_cpu(int cpu)
static void kvm_wait(u8 *ptr, u8 val)
{
- unsigned long flags;
+ bool disabled = irqs_disabled();
if (in_nmi())
return;
- local_irq_save(flags);
+ if (!disabled)
+ local_irq_disable();
if (READ_ONCE(*ptr) != val)
goto out;
@@ -851,13 +852,14 @@ static void kvm_wait(u8 *ptr, u8 val)
* 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))
+ if (disabled)
halt();
else
safe_halt();
out:
- local_irq_restore(flags);
+ if (!disabled)
+ local_irq_enable();
}
#ifdef CONFIG_X86_32
A third option would be to split the paths. In the end, it's only the ptr/val
line that's shared.
---
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
--
I'll send this one tomorrow.
Paolo
