[RFC PATCH v4 28/47] i386/xen: Add support for Xen event channel delivery to vCPU

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

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.
In either of those cases, it returns true to indicate that the work is
done. For other methods it returns false as those would need to be
handled by the caller.

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>
---
 include/sysemu/kvm_xen.h  |  2 ++
 target/i386/kvm/xen-emu.c | 71 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/include/sysemu/kvm_xen.h b/include/sysemu/kvm_xen.h
index 3e43cd7843..d975416f2e 100644
--- a/include/sysemu/kvm_xen.h
+++ b/include/sysemu/kvm_xen.h
@@ -17,6 +17,8 @@
 #define INVALID_GFN UINT64_MAX
 
 uint32_t kvm_xen_get_caps(void);
+void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id);
+bool 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))
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 5932400e61..b01570535e 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -22,6 +22,8 @@
 #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"
 
@@ -274,6 +276,75 @@ static void do_set_vcpu_info_gpa(CPUState *cs, run_on_cpu_data data)
                           env->xen_vcpu_info_gpa);
 }
 
+static void *gpa_to_hva(uint64_t gpa)
+{
+    MemoryRegionSection mrs;
+
+    mrs = memory_region_find(get_system_memory(), gpa, 1);
+    return !mrs.mr ? NULL : qemu_map_ram_ptr(mrs.mr->ram_block,
+                                             mrs.offset_within_region);
+}
+
+void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id)
+{
+    CPUState *cs = qemu_get_cpu(vcpu_id);
+    CPUX86State *env;
+    uint64_t gpa;
+
+    if (!cs) {
+        return NULL;
+    }
+    env = &X86_CPU(cs)->env;
+
+    gpa = env->xen_vcpu_info_gpa;
+    if (gpa == INVALID_GPA) {
+        gpa = env->xen_vcpu_info_default_gpa;
+    }
+    if (gpa == INVALID_GPA) {
+        return NULL;
+    }
+
+    return gpa_to_hva(gpa);
+}
+
+bool 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 false;
+    }
+
+    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 true;
+    }
+
+    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);
+        return true;
+    }
+
+    /* Not handled here. */
+    return false;
+}
+
 static void do_set_vcpu_time_info_gpa(CPUState *cs, run_on_cpu_data data)
 {
     X86CPU *cpu = X86_CPU(cs);
-- 
2.35.3