From: Sean Christopherson seanjc@google.com

commit 3244867af8c065e51969f1bffe732d3ebfd9a7d2 upstream.

Do not bail early if there are no bits set in the sparse banks for a non-sparse, a.k.a. "all CPUs", IPI request. Per the Hyper-V spec, it is legal to have a variable length of '0', e.g. VP_SET's BankContents in this case, if the request can be serviced without the extra info.

It is possible that for a given invocation of a hypercall that does accept variable sized input headers that all the header input fits entirely within the fixed size header. In such cases the variable sized input header is zero-sized and the corresponding bits in the hypercall input should be set to zero.

Bailing early results in KVM failing to send IPIs to all CPUs as expected by the guest.

Fixes: 214ff83d4473 ("KVM: x86: hyperv: implement PV IPI send hypercalls") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com Message-Id: 20211207220926.718794-2-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com --- arch/x86/kvm/hyperv.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index bb39f493447c..328f37e4fd3a 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1641,11 +1641,13 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *current_vcpu, u64 ingpa, u64 outgpa,

all_cpus = send_ipi_ex.vp_set.format == HV_GENERIC_SET_ALL;

+ if (all_cpus) + goto check_and_send_ipi; + if (!sparse_banks_len) goto ret_success;

- if (!all_cpus && - kvm_read_guest(kvm, + if (kvm_read_guest(kvm, ingpa + offsetof(struct hv_send_ipi_ex, vp_set.bank_contents), sparse_banks, @@ -1653,6 +1655,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *current_vcpu, u64 ingpa, u64 outgpa, return HV_STATUS_INVALID_HYPERCALL_INPUT; }

+check_and_send_ipi: if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR)) return HV_STATUS_INVALID_HYPERCALL_INPUT;