[PATCH v7 07/13] confidential guest support: Introduce cgs "ready" flag

David Gibson
2021-01-14T01:53:49Z

The platform specific details of mechanisms for implementing
confidential guest support may require setup at various points during
initialization. Thus, it's not really feasible to have a single cgs
initialization hook, but instead each mechanism needs its own
initialization calls in arch or machine specific code.

However, to make it harder to have a bug where a mechanism isn't
properly initialized under some circumstances, we want to have a
common place, relatively late in boot, where we verify that cgs has
been initialized if it was requested.

This patch introduces a ready flag to the ConfidentialGuestSupport
base type to accomplish this, which we verify just before the machine
specific initialization function.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
hw/core/machine.c | 8 ++++++++
include/exec/confidential-guest-support.h | 2 ++
target/i386/sev.c | 2 ++
3 files changed, 12 insertions(+)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 94194ab82d..5a7433332b 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1190,6 +1190,14 @@ void machine_run_board_init(MachineState *machine)
}

if (machine->cgs) {
+ /*
+ * Where confidential guest support is initialized depends on
+ * the specific mechanism in use. But, we need to make sure
+ * it's ready by now. If it isn't, that's a bug in the
+ * implementation of that cgs mechanism.
+ */
+ assert(machine->cgs->ready);
+
/*
* With confidential guests, the host can't see the real
* contents of RAM, so there's no point in it trying to merge
diff --git a/include/exec/confidential-guest-support.h b/include/exec/confidential-guest-support.h
index 5f131023ba..bcaf6c9f49 100644
--- a/include/exec/confidential-guest-support.h
+++ b/include/exec/confidential-guest-support.h
@@ -27,6 +27,8 @@ OBJECT_DECLARE_SIMPLE_TYPE(ConfidentialGuestSupport, CONFIDENTIAL_GUEST_SUPPORT)

struct ConfidentialGuestSupport {
Object parent;
+
+ bool ready;
};

typedef struct ConfidentialGuestSupportClass {
diff --git a/target/i386/sev.c b/target/i386/sev.c
index e2b41ef342..3d94635397 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -737,6 +737,8 @@ int sev_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
qemu_add_machine_init_done_notifier(&sev_machine_done_notify);
qemu_add_vm_change_state_handler(sev_vm_state_change, sev);

+ cgs->ready = true;
+
return 0;
err:
sev_guest = NULL;
--
2.29.2