Author: royger
Date: Tue Nov 12 10:31:28 2019
New Revision: 354637
URL: https://svnweb.freebsd.org/changeset/base/354637

Log:
  xen: fix dispatching of NMIs
  
  Currently NMIs are sent over event channels, but that defeats the
  purpose of NMIs since event channels can be masked. Fix this by
  issuing NMIs using a hypercall, which injects a NMI (vector #2) to the
  desired vCPU.
  
  Note that NMIs could also be triggered using the emulated local APIC,
  but using a hypercall is better from a performance point of view
  since it doesn't involve instruction decoding when not using x2APIC
  mode.
  
  Reported and Tested by:       avg
  Sponsored by:         Citrix Systems R&D

Modified:
  head/sys/x86/xen/xen_apic.c

Modified: head/sys/x86/xen/xen_apic.c
==============================================================================
--- head/sys/x86/xen/xen_apic.c Tue Nov 12 10:22:48 2019        (r354636)
+++ head/sys/x86/xen/xen_apic.c Tue Nov 12 10:31:28 2019        (r354637)
@@ -72,7 +72,6 @@ static driver_filter_t xen_invlcache;
 static driver_filter_t xen_ipi_bitmap_handler;
 static driver_filter_t xen_cpustop_handler;
 static driver_filter_t xen_cpususpend_handler;
-static driver_filter_t xen_cpustophard_handler;
 #endif
 
 /*---------------------------------- Macros 
----------------------------------*/
@@ -96,7 +95,6 @@ static struct xen_ipi_handler xen_ipis[] = 
        [IPI_TO_IDX(IPI_BITMAP_VECTOR)] = { xen_ipi_bitmap_handler,     "b"   },
        [IPI_TO_IDX(IPI_STOP)]          = { xen_cpustop_handler,        "st"  },
        [IPI_TO_IDX(IPI_SUSPEND)]       = { xen_cpususpend_handler,     "sp"  },
-       [IPI_TO_IDX(IPI_STOP_HARD)]     = { xen_cpustophard_handler,    "sth" },
 };
 #endif
 
@@ -259,12 +257,52 @@ xen_pv_lapic_ipi_raw(register_t icrlo, u_int dest)
        XEN_APIC_UNSUPPORTED;
 }
 
+#define PCPU_ID_GET(id, field) (pcpu_find(id)->pc_##field)
 static void
+send_nmi(int dest)
+{
+       unsigned int cpu;
+
+       /*
+        * NMIs are not routed over event channels, and instead delivered as on
+        * native using the exception vector (#2). Triggering them can be done
+        * using the local APIC, or an hypercall as a shortcut like it's done
+        * below.
+        */
+       switch(dest) {
+       case APIC_IPI_DEST_SELF:
+               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,
+                           PCPU_ID_GET(cpu, vcpu_id), NULL);
+               break;
+       case APIC_IPI_DEST_OTHERS:
+               CPU_FOREACH(cpu)
+                       if (cpu != PCPU_GET(cpuid))
+                               HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
+                                   PCPU_ID_GET(cpu, vcpu_id), NULL);
+               break;
+       default:
+               HYPERVISOR_vcpu_op(VCPUOP_send_nmi,
+                   PCPU_ID_GET(apic_cpuid(dest), vcpu_id), NULL);
+               break;
+       }
+}
+#undef PCPU_ID_GET
+
+static void
 xen_pv_lapic_ipi_vectored(u_int vector, int dest)
 {
        xen_intr_handle_t *ipi_handle;
        int ipi_idx, to_cpu, self;
 
+       if (vector >= IPI_NMI_FIRST) {
+               send_nmi(dest);
+               return;
+       }
+
        ipi_idx = IPI_TO_IDX(vector);
        if (ipi_idx >= nitems(xen_ipis))
                panic("IPI out of range");
@@ -519,14 +557,6 @@ xen_cpususpend_handler(void *arg)
 {
 
        cpususpend_handler();
-       return (FILTER_HANDLED);
-}
-
-static int
-xen_cpustophard_handler(void *arg)
-{
-
-       ipi_nmi_handler();
        return (FILTER_HANDLED);
 }
 
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