i386/xen: Add support for Xen event channel delivery to vCPU

The kvm_xen_inject_vcpu_callback_vector() function will either deliver
the per-vCPU local APIC vector (as an MSI), or just kick the vCPU out
of the kernel to trigger KVM's automatic delivery of the global vector.
Support for asserting the GSI/PCI_INTX callbacks will come later.

Also add kvm_xen_get_vcpu_info_hva() which returns the vcpu_info of
a given vCPU.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

include/sysemu/kvm_xen.h

@@ -21,6 +21,8 @@
 
 int kvm_xen_soft_reset(void);
 uint32_t kvm_xen_get_caps(void);
+void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id);
+void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type);
 
 #define kvm_xen_has_cap(cap) (!!(kvm_xen_get_caps() &           \
                                  KVM_XEN_HVM_CONFIG_ ## cap))

target/i386/cpu.h

@@ -1799,6 +1799,8 @@ typedef struct CPUArchState {
 #endif
 #if defined(CONFIG_KVM)
     struct kvm_nested_state *nested_state;
+    MemoryRegion *xen_vcpu_info_mr;
+    void *xen_vcpu_info_hva;
     uint64_t xen_vcpu_info_gpa;
     uint64_t xen_vcpu_info_default_gpa;
     uint64_t xen_vcpu_time_info_gpa;

target/i386/kvm/xen-emu.c

@@ -21,6 +21,8 @@
 #include "trace.h"
 #include "sysemu/runstate.h"
 
+#include "hw/pci/msi.h"
+#include "hw/i386/apic-msidef.h"
 #include "hw/i386/kvm/xen_overlay.h"
 #include "hw/i386/kvm/xen_evtchn.h"
 
@@ -248,6 +250,43 @@ static void do_set_vcpu_callback_vector(CPUState *cs, run_on_cpu_data data)
     }
 }
 
+static int set_vcpu_info(CPUState *cs, uint64_t gpa)
+{
+    X86CPU *cpu = X86_CPU(cs);
+    CPUX86State *env = &cpu->env;
+    MemoryRegionSection mrs = { .mr = NULL };
+    void *vcpu_info_hva = NULL;
+    int ret;
+
+    ret = kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO, gpa);
+    if (ret || gpa == INVALID_GPA) {
+        goto out;
+    }
+
+    mrs = memory_region_find(get_system_memory(), gpa,
+                             sizeof(struct vcpu_info));
+    if (mrs.mr && mrs.mr->ram_block &&
+        !int128_lt(mrs.size, int128_make64(sizeof(struct vcpu_info)))) {
+        vcpu_info_hva = qemu_map_ram_ptr(mrs.mr->ram_block,
+                                         mrs.offset_within_region);
+    }
+    if (!vcpu_info_hva) {
+        if (mrs.mr) {
+            memory_region_unref(mrs.mr);
+            mrs.mr = NULL;
+        }
+        ret = -EINVAL;
+    }
+
+ out:
+    if (env->xen_vcpu_info_mr) {
+        memory_region_unref(env->xen_vcpu_info_mr);
+    }
+    env->xen_vcpu_info_hva = vcpu_info_hva;
+    env->xen_vcpu_info_mr = mrs.mr;
+    return ret;
+}
+
 static void do_set_vcpu_info_default_gpa(CPUState *cs, run_on_cpu_data data)
 {
     X86CPU *cpu = X86_CPU(cs);
@@ -257,8 +296,7 @@ static void do_set_vcpu_info_default_gpa(CPUState *cs, run_on_cpu_data data)
 
     /* Changing the default does nothing if a vcpu_info was explicitly set. */
     if (env->xen_vcpu_info_gpa == INVALID_GPA) {
-        kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO,
-                              env->xen_vcpu_info_default_gpa);
+        set_vcpu_info(cs, env->xen_vcpu_info_default_gpa);
     }
 }
 
@@ -269,8 +307,52 @@ static void do_set_vcpu_info_gpa(CPUState *cs, run_on_cpu_data data)
 
     env->xen_vcpu_info_gpa = data.host_ulong;
 
-    kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO,
-                          env->xen_vcpu_info_gpa);
+    set_vcpu_info(cs, env->xen_vcpu_info_gpa);
+}
+
+void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id)
+{
+    CPUState *cs = qemu_get_cpu(vcpu_id);
+    if (!cs) {
+        return NULL;
+    }
+
+    return X86_CPU(cs)->env.xen_vcpu_info_hva;
+}
+
+void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type)
+{
+    CPUState *cs = qemu_get_cpu(vcpu_id);
+    uint8_t vector;
+
+    if (!cs) {
+        return;
+    }
+
+    vector = X86_CPU(cs)->env.xen_vcpu_callback_vector;
+    if (vector) {
+        /*
+         * The per-vCPU callback vector injected via lapic. Just
+         * deliver it as an MSI.
+         */
+        MSIMessage msg = {
+            .address = APIC_DEFAULT_ADDRESS | X86_CPU(cs)->apic_id,
+            .data = vector | (1UL << MSI_DATA_LEVEL_SHIFT),
+        };
+        kvm_irqchip_send_msi(kvm_state, msg);
+        return;
+    }
+
+    switch (type) {
+    case HVM_PARAM_CALLBACK_TYPE_VECTOR:
+        /*
+         * If the evtchn_upcall_pending field in the vcpu_info is set, then
+         * KVM will automatically deliver the vector on entering the vCPU
+         * so all we have to do is kick it out.
+         */
+        qemu_cpu_kick(cs);
+        break;
+    }
 }
 
 static void do_set_vcpu_time_info_gpa(CPUState *cs, run_on_cpu_data data)
@@ -306,7 +388,7 @@ static void do_vcpu_soft_reset(CPUState *cs, run_on_cpu_data data)
     env->xen_vcpu_runstate_gpa = INVALID_GPA;
     env->xen_vcpu_callback_vector = 0;
 
-    kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO, INVALID_GPA);
+    set_vcpu_info(cs, INVALID_GPA);
     kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO,
                           INVALID_GPA);
     kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR,
@@ -903,7 +985,7 @@ int kvm_put_xen_state(CPUState *cs)
     }
 
     if (gpa != INVALID_GPA) {
-        ret = kvm_xen_set_vcpu_attr(cs, KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO, gpa);
+        ret = set_vcpu_info(cs, gpa);
         if (ret < 0) {
             return ret;
         }