[PATCH] x86/hyper-v: fix hypercalls with extended CPU ranges for TLB flushing

[Marcelo Henrique Cerri]

Do not consider the fixed size of hv_vp_set when passing the variable
header size to hv_do_rep_hypercall().

The Hyper-V hypervisor specification states that for a hypercall with a
variable header only the size of the variable portion should be supplied
via the input control.

For HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX/LIST_EX calls that means the
fixed portion of hv_vp_set should not be considered.

That fixes random failures of some applications that are unexpectedly
killed with SIGBUS or SIGSEGV.

Fixes: 628f54cc6451 ("x86/hyper-v: Support extended CPU ranges for TLB flush 
hypercalls")
Signed-off-by: Marcelo Henrique Cerri <marcelo.ce...@canonical.com>
---
 arch/x86/hyperv/mmu.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index 39e7f6e50919..123d9b501108 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c
@@ -222,18 +222,18 @@ static void hyperv_flush_tlb_others_ex(const struct 
cpumask *cpus,
                flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY;
                status = hv_do_rep_hypercall(
                        HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX,
-                       0, nr_bank + 2, flush, NULL);
+                       0, nr_bank, flush, NULL);
        } else if (info->end &&
                   ((info->end - info->start)/HV_TLB_FLUSH_UNIT) > max_gvas) {
                status = hv_do_rep_hypercall(
                        HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX,
-                       0, nr_bank + 2, flush, NULL);
+                       0, nr_bank, flush, NULL);
        } else {
                gva_n = fill_gva_list(flush->gva_list, nr_bank,
                                      info->start, info->end);
                status = hv_do_rep_hypercall(
                        HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX,
-                       gva_n, nr_bank + 2, flush, NULL);
+                       gva_n, nr_bank, flush, NULL);
        }
 
        local_irq_restore(flags);
-- 
2.7.4