x86/hyper-v: Check for VP_INVAL in hyperv_flush_tlb_others()

Commit 1268ed0 ("x86/hyper-v: Fix the circular dependency in IPI
 enlightenment") pre-filled hv_vp_index with VP_INVAL so it is now
(theoretically) possible to observe hv_cpu_number_to_vp_number()
returning VP_INVAL. We need to check for that in hyperv_flush_tlb_others().

Not checking for VP_INVAL on the first call site where we do

 if (hv_cpu_number_to_vp_number(cpumask_last(cpus)) >= 64)
                        goto do_ex_hypercall;

is OK, in case we're eligible for non-ex hypercall we'll catch the
issue later in for_each_cpu() cycle and in case we'll be doing ex-
hypercall cpumask_to_vpset() will fail.

It would be nice to change hv_cpu_number_to_vp_number() return
value's type to 'u32' but this will likely be a bigger change as
all call sites need to be checked first.

Fixes: 1268ed0 ("x86/hyper-v: Fix the circular dependency in IPI enlightenment")
Signed-off-by: Vitaly Kuznetsov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Michael Kelley <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: "Michael Kelley (EOSG)" <[email protected]>
Cc: [email protected]
Cc: "H. Peter Anvin" <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: vittyvk

arch/x86/hyperv/mmu.c

@@ -111,6 +111,11 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,
 
 		for_each_cpu(cpu, cpus) {
 			vcpu = hv_cpu_number_to_vp_number(cpu);
+			if (vcpu == VP_INVAL) {
+				local_irq_restore(flags);
+				goto do_native;
+			}
+
 			if (vcpu >= 64)
 				goto do_ex_hypercall;