[PATCH v8 08/13] confidential guest support: Move SEV initialization into arch specific code

[David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
---
 accel/kvm/kvm-all.c   | 14 --------------
 accel/kvm/sev-stub.c  |  4 ++--
 target/i386/kvm/kvm.c | 20 ++++++++++++++++++++
 target/i386/sev.c     |  7 ++++++-
 4 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 3d820d0c7d..7150acdbcc 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__);
-- 
2.29.2