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x86/xen: fallback when VCPUOP_send_nmi is not available

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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: b2802351c162 ('xen: fix dispatching of NMIs')
Sponsored by: Citrix Systems R&D
This commit is contained in:
Roger Pau Monné 2022-01-13 14:48:14 +01:00
parent 779fd05344
commit ad15eeeaba
1 changed files with 41 additions and 11 deletions
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52
sys/x86/xen/xen_apic.c
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@ -107,6 +107,14 @@ static struct xen_ipi_handler xen_ipis[] =
};
#endif
/*
* Save previous (native) handler as a fallback. Xen < 4.7 doesn't support
* VCPUOP_send_nmi for HVM guests, and thus we need a fallback in that case:
*
* https://lists.freebsd.org/archives/freebsd-xen/2022-January/000032.html
*/
void (*native_ipi_vectored)(u_int, int);
/*------------------------------- Per-CPU Data -------------------------------*/
#ifdef SMP
DPCPU_DEFINE(xen_intr_handle_t, ipi_handle[nitems(xen_ipis)]);
@ -273,10 +281,11 @@ xen_pv_lapic_ipi_raw(register_t icrlo, u_int dest)
}
#define PCPU_ID_GET(id, field) (pcpu_find(id)->pc_##field)
static void
static int
send_nmi(int dest)
{
unsigned int cpu;
int rc = 0;
/*
* NMIs are not routed over event channels, and instead delivered as on
@ -286,24 +295,33 @@ send_nmi(int dest)
*/
switch(dest) {
case APIC_IPI_DEST_SELF:
HYPERVISOR_vcpu_op(VCPUOP_send_nmi, PCPU_GET(vcpu_id), NULL);
rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi, PCPU_GET(vcpu_id), NULL);
break;
case APIC_IPI_DEST_ALL:
CPU_FOREACH(cpu)
HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
CPU_FOREACH(cpu) {
rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
PCPU_ID_GET(cpu, vcpu_id), NULL);
if (rc != 0)
break;
}
break;
case APIC_IPI_DEST_OTHERS:
CPU_FOREACH(cpu)
if (cpu != PCPU_GET(cpuid))
HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
CPU_FOREACH(cpu) {
if (cpu != PCPU_GET(cpuid)) {
rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
PCPU_ID_GET(cpu, vcpu_id), NULL);
if (rc != 0)
break;
}
}
break;
default:
HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
rc = HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
PCPU_ID_GET(apic_cpuid(dest), vcpu_id), NULL);
break;
}
return rc;
}
#undef PCPU_ID_GET
@ -312,9 +330,21 @@ xen_pv_lapic_ipi_vectored(u_int vector, int dest)
{
xen_intr_handle_t *ipi_handle;
int ipi_idx, to_cpu, self;
static bool pvnmi = true;
if (vector >= IPI_NMI_FIRST) {
send_nmi(dest);
if (pvnmi) {
int rc = send_nmi(dest);
if (rc != 0) {
printf(
"Sending NMI using hypercall failed (%d) switching to APIC\n", rc);
pvnmi = false;
native_ipi_vectored(vector, dest);
}
} else
native_ipi_vectored(vector, dest);
return;
}
@ -580,8 +610,8 @@ xen_setup_cpus(void)
xen_cpu_ipi_init(i);
/* Set the xen pv ipi ops to replace the native ones */
if (xen_hvm_domain())
apic_ops.ipi_vectored = xen_pv_lapic_ipi_vectored;
native_ipi_vectored = apic_ops.ipi_vectored;
apic_ops.ipi_vectored = xen_pv_lapic_ipi_vectored;
}
/* Switch to using PV IPIs as soon as the vcpu_id is set. */