Commit ad0a6bad authored by Wei Liu's avatar Wei Liu
Browse files

x86/hyperv: check cpu mask after interrupt has been disabled 



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: default avatarWei Liu <wei.liu@kernel.org>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20210105175043.28325-1-wei.liu@kernel.org


Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
parent dfe94d40

arch/x86/hyperv/mmu.c

+9 −3
Original line number Diff line number Diff line
@@ -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);