Zero out the valid_bank_mask when using the fast variant of HVCALL_SEND_IPI_EX to send IPIs to all vCPUs. KVM requires the "var_cnt" and "valid_bank_mask" inputs to be consistent even when targeting all vCPUs. See commit bd1ba5732bb9 ("KVM: x86: Get the number of Hyper-V sparse banks from the VARHEAD field"). Fixes: 998489245d84 ("KVM: selftests: Hyper-V PV IPI selftest") Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- tools/testing/selftests/kvm/x86_64/hyperv_ipi.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_ipi.c b/tools/testing/selftests/kvm/x86_64/hyperv_ipi.c index 8b791eac7d5a..0cbb0e646ef8 100644 --- a/tools/testing/selftests/kvm/x86_64/hyperv_ipi.c +++ b/tools/testing/selftests/kvm/x86_64/hyperv_ipi.c @@ -193,8 +193,9 @@ static void sender_guest_code(void *hcall_page, vm_vaddr_t pgs_gpa) GUEST_SYNC(stage++); /* * 'XMM Fast' HvCallSendSyntheticClusterIpiEx to HV_GENERIC_SET_ALL. - * Nothing to write anything to XMM regs. */ + ipi_ex->vp_set.valid_bank_mask = 0; + hyperv_write_xmm_input(&ipi_ex->vp_set.valid_bank_mask, 2); hyperv_hypercall(HVCALL_SEND_IPI_EX | HV_HYPERCALL_FAST_BIT, IPI_VECTOR, HV_GENERIC_SET_ALL); nop_loop(); base-commit: 9d75a3251adfbcf444681474511b58042a364863 -- 2.39.0.314.g84b9a713c41-goog