i386/xen: handle HVMOP_get_param

Which is used to fetch xenstore PFN and port to be used
by the guest. This is preallocated by the toolstack when
guest will just read those and use it straight away.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 75bcf7b..d2c88ef 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -765,6 +765,42 @@ out:
     return true;
 }
 
+static bool handle_get_param(struct kvm_xen_exit *exit, X86CPU *cpu,
+                             uint64_t arg)
+{
+    CPUState *cs = CPU(cpu);
+    struct xen_hvm_param hp;
+    int err = 0;
+
+    /* No need for 32/64 compat handling */
+    qemu_build_assert(sizeof(hp) == 16);
+
+    if (kvm_copy_from_gva(cs, arg, &hp, sizeof(hp))) {
+        err = -EFAULT;
+        goto out;
+    }
+
+    if (hp.domid != DOMID_SELF && hp.domid != xen_domid) {
+        err = -ESRCH;
+        goto out;
+    }
+
+    switch (hp.index) {
+    case HVM_PARAM_STORE_PFN:
+        hp.value = XEN_SPECIAL_PFN(XENSTORE);
+        break;
+    default:
+        return false;
+    }
+
+    if (kvm_copy_to_gva(cs, arg, &hp, sizeof(hp))) {
+        err = -EFAULT;
+    }
+out:
+    exit->u.hcall.result = err;
+    return true;
+}
+
 static int kvm_xen_hcall_evtchn_upcall_vector(struct kvm_xen_exit *exit,
                                               X86CPU *cpu, uint64_t arg)
 {
@@ -809,6 +845,9 @@ static bool kvm_xen_hcall_hvm_op(struct kvm_xen_exit *exit, X86CPU *cpu,
     case HVMOP_set_param:
         return handle_set_param(exit, cpu, arg);
 
+    case HVMOP_get_param:
+        return handle_get_param(exit, cpu, arg);
+
     default:
         return false;
     }