x86/xen: fallback when VCPUOP_send_nmi is not available
It has been reported that on some AWS instances VCPUOP_send_nmi
returns -38 (ENOSYS). The hypercall is only available for HVM guests
in Xen 4.7 and newer. Add a fallback to use the native NMI sending
procedure when VCPUOP_send_nmi is not available, so that the NMI is
not lost.
Reported and Tested by: avg
MFC after: 1 week
Fixes: b2802351c1
('xen: fix dispatching of NMIs')
Sponsored by: Citrix Systems R&D
This commit is contained in:
parent
779fd05344
commit
ad15eeeaba
@ -107,6 +107,14 @@ static struct xen_ipi_handler xen_ipis[] =
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};
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#endif
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/*
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* Save previous (native) handler as a fallback. Xen < 4.7 doesn't support
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* VCPUOP_send_nmi for HVM guests, and thus we need a fallback in that case:
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*
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* https://lists.freebsd.org/archives/freebsd-xen/2022-January/000032.html
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*/
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void (*native_ipi_vectored)(u_int, int);
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/*------------------------------- Per-CPU Data -------------------------------*/
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#ifdef SMP
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DPCPU_DEFINE(xen_intr_handle_t, ipi_handle[nitems(xen_ipis)]);
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@ -273,10 +281,11 @@ xen_pv_lapic_ipi_raw(register_t icrlo, u_int dest)
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}
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#define PCPU_ID_GET(id, field) (pcpu_find(id)->pc_##field)
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static void
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static int
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send_nmi(int dest)
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{
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unsigned int cpu;
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int rc = 0;
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/*
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* NMIs are not routed over event channels, and instead delivered as on
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@ -286,24 +295,33 @@ send_nmi(int dest)
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*/
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switch(dest) {
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case APIC_IPI_DEST_SELF:
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HYPERVISOR_vcpu_op(VCPUOP_send_nmi, PCPU_GET(vcpu_id), NULL);
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rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi, PCPU_GET(vcpu_id), NULL);
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break;
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case APIC_IPI_DEST_ALL:
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CPU_FOREACH(cpu)
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HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
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CPU_FOREACH(cpu) {
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rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
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PCPU_ID_GET(cpu, vcpu_id), NULL);
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if (rc != 0)
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break;
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}
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break;
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case APIC_IPI_DEST_OTHERS:
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CPU_FOREACH(cpu)
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if (cpu != PCPU_GET(cpuid))
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HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
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CPU_FOREACH(cpu) {
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if (cpu != PCPU_GET(cpuid)) {
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rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
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PCPU_ID_GET(cpu, vcpu_id), NULL);
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if (rc != 0)
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break;
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}
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}
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break;
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default:
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HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
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rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
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PCPU_ID_GET(apic_cpuid(dest), vcpu_id), NULL);
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break;
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}
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return rc;
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}
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#undef PCPU_ID_GET
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@ -312,9 +330,21 @@ xen_pv_lapic_ipi_vectored(u_int vector, int dest)
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{
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xen_intr_handle_t *ipi_handle;
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int ipi_idx, to_cpu, self;
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static bool pvnmi = true;
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if (vector >= IPI_NMI_FIRST) {
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send_nmi(dest);
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if (pvnmi) {
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int rc = send_nmi(dest);
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if (rc != 0) {
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printf(
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"Sending NMI using hypercall failed (%d) switching to APIC\n", rc);
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pvnmi = false;
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native_ipi_vectored(vector, dest);
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}
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} else
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native_ipi_vectored(vector, dest);
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return;
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}
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@ -580,8 +610,8 @@ xen_setup_cpus(void)
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xen_cpu_ipi_init(i);
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/* Set the xen pv ipi ops to replace the native ones */
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if (xen_hvm_domain())
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apic_ops.ipi_vectored = xen_pv_lapic_ipi_vectored;
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native_ipi_vectored = apic_ops.ipi_vectored;
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apic_ops.ipi_vectored = xen_pv_lapic_ipi_vectored;
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}
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/* Switch to using PV IPIs as soon as the vcpu_id is set. */
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