confidential guest support: Move SEV initialization into arch specific code

While we've abstracted some (potential) differences between mechanisms for
securing guest memory, the initialization is still specific to SEV.  Given
that, move it into x86's kvm_arch_init() code, rather than the generic
kvm_init() code.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>

4 files changed, 28 insertions, 17 deletions

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 226e1556f9..e72a19aaf8 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2180,20 +2180,6 @@ static int kvm_init(MachineState *ms)
 
     kvm_state = s;
 
-    /*
-     * if memory encryption object is specified then initialize the memory
-     * encryption context.
-     */
-    if (ms->cgs) {
-        Error *local_err = NULL;
-        /* FIXME handle mechanisms other than SEV */
-        ret = sev_kvm_init(ms->cgs, &local_err);
-        if (ret < 0) {
-            error_report_err(local_err);
-            goto err;
-        }
-    }
-
     ret = kvm_arch_init(ms, s);
     if (ret < 0) {
         goto err;
diff --git a/accel/kvm/sev-stub.c b/accel/kvm/sev-stub.c
index 512e205f7f..9587d1b2a3 100644
--- a/accel/kvm/sev-stub.c
+++ b/accel/kvm/sev-stub.c
@@ -17,6 +17,6 @@
 
 int sev_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
 {
-    /* SEV can't be selected if it's not compiled */
-    g_assert_not_reached();
+    /* If we get here, cgs must be some non-SEV thing */
+    return 0;
 }
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 6dc1ee052d..4788139128 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -42,6 +42,7 @@
 #include "hw/i386/intel_iommu.h"
 #include "hw/i386/x86-iommu.h"
 #include "hw/i386/e820_memory_layout.h"
+#include "sysemu/sev.h"
 
 #include "hw/pci/pci.h"
 #include "hw/pci/msi.h"
@@ -2135,6 +2136,25 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     uint64_t shadow_mem;
     int ret;
     struct utsname utsname;
+    Error *local_err = NULL;
+
+    /*
+     * Initialize SEV context, if required
+     *
+     * If no memory encryption is requested (ms->cgs == NULL) this is
+     * a no-op.
+     *
+     * It's also a no-op if a non-SEV confidential guest support
+     * mechanism is selected.  SEV is the only mechanism available to
+     * select on x86 at present, so this doesn't arise, but if new
+     * mechanisms are supported in future (e.g. TDX), they'll need
+     * their own initialization either here or elsewhere.
+     */
+    ret = sev_kvm_init(ms->cgs, &local_err);
+    if (ret < 0) {
+        error_report_err(local_err);
+        return ret;
+    }
 
     if (!kvm_check_extension(s, KVM_CAP_IRQ_ROUTING)) {
         error_report("kvm: KVM_CAP_IRQ_ROUTING not supported by KVM");
diff --git a/target/i386/sev.c b/target/i386/sev.c
index f9e9b5d8ae..11c9a3cc21 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -664,13 +664,18 @@ sev_vm_state_change(void *opaque, int running, RunState state)
 
 int sev_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
 {
-    SevGuestState *sev = SEV_GUEST(cgs);
+    SevGuestState *sev
+        = (SevGuestState *)object_dynamic_cast(OBJECT(cgs), TYPE_SEV_GUEST);
     char *devname;
     int ret, fw_error;
     uint32_t ebx;
     uint32_t host_cbitpos;
     struct sev_user_data_status status = {};
 
+    if (!sev) {
+        return 0;
+    }
+
     ret = ram_block_discard_disable(true);
     if (ret) {
         error_report("%s: cannot disable RAM discard", __func__);