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    Subject[PATCH 5.15 777/913] KVM: x86: hyper-v: HVCALL_SEND_IPI_EX is an XMM fast hypercall
    Date
    From: Vitaly Kuznetsov <vkuznets@redhat.com>

    commit 47d3e5cdfe607ec6883eb0faa7acf05b8cb3f92a upstream.

    It has been proven on practice that at least Windows Server 2019 tries
    using HVCALL_SEND_IPI_EX in 'XMM fast' mode when it has more than 64 vCPUs
    and it needs to send an IPI to a vCPU > 63. Similarly to other XMM Fast
    hypercalls (HVCALL_FLUSH_VIRTUAL_ADDRESS_{LIST,SPACE}{,_EX}), this
    information is missing in TLFS as of 6.0b. Currently, KVM returns an error
    (HV_STATUS_INVALID_HYPERCALL_INPUT) and Windows crashes.

    Note, HVCALL_SEND_IPI is a 'standard' fast hypercall (not 'XMM fast') as
    all its parameters fit into RDX:R8 and this is handled by KVM correctly.

    Cc: stable@vger.kernel.org # 5.14.x: 3244867af8c0: KVM: x86: Ignore sparse banks size for an "all CPUs", non-sparse IPI req
    Cc: stable@vger.kernel.org # 5.14.x
    Fixes: d8f5537a8816 ("KVM: hyper-v: Advertise support for fast XMM hypercalls")
    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    Message-Id: <20220222154642.684285-5-vkuznets@redhat.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kvm/hyperv.c | 52 ++++++++++++++++++++++++++++++++------------------
    1 file changed, 34 insertions(+), 18 deletions(-)

    --- a/arch/x86/kvm/hyperv.c
    +++ b/arch/x86/kvm/hyperv.c
    @@ -1889,6 +1889,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vc
    int sparse_banks_len;
    u32 vector;
    bool all_cpus;
    + int i;

    if (hc->code == HVCALL_SEND_IPI) {
    if (!hc->fast) {
    @@ -1909,9 +1910,15 @@ static u64 kvm_hv_send_ipi(struct kvm_vc

    trace_kvm_hv_send_ipi(vector, sparse_banks[0]);
    } else {
    - if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi_ex,
    - sizeof(send_ipi_ex))))
    - return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + if (!hc->fast) {
    + if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi_ex,
    + sizeof(send_ipi_ex))))
    + return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + } else {
    + send_ipi_ex.vector = (u32)hc->ingpa;
    + send_ipi_ex.vp_set.format = hc->outgpa;
    + send_ipi_ex.vp_set.valid_bank_mask = sse128_lo(hc->xmm[0]);
    + }

    trace_kvm_hv_send_ipi_ex(send_ipi_ex.vector,
    send_ipi_ex.vp_set.format,
    @@ -1919,8 +1926,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vc

    vector = send_ipi_ex.vector;
    valid_bank_mask = send_ipi_ex.vp_set.valid_bank_mask;
    - sparse_banks_len = bitmap_weight(&valid_bank_mask, 64) *
    - sizeof(sparse_banks[0]);
    + sparse_banks_len = bitmap_weight(&valid_bank_mask, 64);

    all_cpus = send_ipi_ex.vp_set.format == HV_GENERIC_SET_ALL;

    @@ -1930,12 +1936,27 @@ static u64 kvm_hv_send_ipi(struct kvm_vc
    if (!sparse_banks_len)
    goto ret_success;

    - if (kvm_read_guest(kvm,
    - hc->ingpa + offsetof(struct hv_send_ipi_ex,
    - vp_set.bank_contents),
    - sparse_banks,
    - sparse_banks_len))
    - return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + if (!hc->fast) {
    + if (kvm_read_guest(kvm,
    + hc->ingpa + offsetof(struct hv_send_ipi_ex,
    + vp_set.bank_contents),
    + sparse_banks,
    + sparse_banks_len * sizeof(sparse_banks[0])))
    + return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + } else {
    + /*
    + * The lower half of XMM0 is already consumed, each XMM holds
    + * two sparse banks.
    + */
    + if (sparse_banks_len > (2 * HV_HYPERCALL_MAX_XMM_REGISTERS - 1))
    + return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + for (i = 0; i < sparse_banks_len; i++) {
    + if (i % 2)
    + sparse_banks[i] = sse128_lo(hc->xmm[(i + 1) / 2]);
    + else
    + sparse_banks[i] = sse128_hi(hc->xmm[i / 2]);
    + }
    + }
    }

    check_and_send_ipi:
    @@ -2097,6 +2118,7 @@ static bool is_xmm_fast_hypercall(struct
    case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE:
    case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX:
    case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX:
    + case HVCALL_SEND_IPI_EX:
    return true;
    }

    @@ -2264,14 +2286,8 @@ int kvm_hv_hypercall(struct kvm_vcpu *vc
    ret = kvm_hv_flush_tlb(vcpu, &hc);
    break;
    case HVCALL_SEND_IPI:
    - if (unlikely(hc.rep)) {
    - ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
    - break;
    - }
    - ret = kvm_hv_send_ipi(vcpu, &hc);
    - break;
    case HVCALL_SEND_IPI_EX:
    - if (unlikely(hc.fast || hc.rep)) {
    + if (unlikely(hc.rep)) {
    ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
    break;
    }

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