We've observed crashes due to an empty cpu mask in
hyperv_flush_tlb_others. Obviously the cpu mask in question is changed
between the cpumask_empty call at the beginning of the function and when
it is actually used later.
One theory is that an interrupt comes in between and a code path ends up
changing the mask. Move the check after interrupt has been disabled to
see if it fixes the issue.
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
---
arch/x86/hyperv/mmu.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index 5208ba49c89a..2c87350c1fb0 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c
@@ -66,11 +66,17 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,
if (!hv_hypercall_pg)
goto do_native;
- if (cpumask_empty(cpus))
- return;
-
local_irq_save(flags);
+ /*
+ * Only check the mask _after_ interrupt has been disabled to avoid the
+ * mask changing under our feet.
+ */
+ if (cpumask_empty(cpus)) {
+ local_irq_restore(flags);
+ return;
+ }
+
flush_pcpu = (struct hv_tlb_flush **)
this_cpu_ptr(hyperv_pcpu_input_arg);
--
2.20.1
