RE: [PATCH] x86/hyper-v: guard against cpu mask changes in hyperv_flush_tlb_others()

Attaching the patches Michael asked for debugging 
1) Print the cpumask when < num_possible_cpus():

diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index e666f7eaf32d..620f656d6195 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c

@@ -60,6 +60,7 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,

        struct hv_tlb_flush *flush;
        u64 status = U64_MAX;
        unsigned long flags;
+       unsigned int cpu_last;

       trace_hyperv_mmu_flush_tlb_others(cpus, info);

@@ -68,6 +69,11 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,

       local_irq_save(flags);

+       cpu_last = cpumask_last(cpus);
+       if (cpu_last > num_possible_cpus()) {

+               pr_emerg("ERROR_HYPERV: cpu_last=%*pbl", cpumask_pr_args(cpus));
+       }
+
       /*
        * Only check the mask _after_ interrupt has been disabled to avoid the
        * mask changing under our feet.

2) disable the Hyper-V specific flush routines:

diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index e666f7eaf32d..8e77cc84775a 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c

@@ -235,6 +235,7 @@ static u64 hyperv_flush_tlb_others_ex(const struct cpumask *cpus,

void hyperv_setup_mmu_ops(void)
{
+  return;
       if (!(ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED))
               return;