From abc27d4241f99bfaebb0b843b9a967d557ac10e8 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Tue, 20 Oct 2020 17:01:19 +1100 Subject: [PATCH] confidential guest support: Introduce cgs "ready" flag 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, 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 in qemu_machine_creation_done(). Signed-off-by: David Gibson Reviewed-by: Dr. David Alan Gilbert Reviewed-by: Greg Kurz --- include/exec/confidential-guest-support.h | 24 +++++++++++++++++++++++ softmmu/vl.c | 10 ++++++++++ target/i386/sev.c | 2 ++ 3 files changed, 36 insertions(+) diff --git a/include/exec/confidential-guest-support.h b/include/exec/confidential-guest-support.h index 3db6380e63..ba2dd4b5df 100644 --- a/include/exec/confidential-guest-support.h +++ b/include/exec/confidential-guest-support.h @@ -27,6 +27,30 @@ OBJECT_DECLARE_SIMPLE_TYPE(ConfidentialGuestSupport, CONFIDENTIAL_GUEST_SUPPORT) struct ConfidentialGuestSupport { Object parent; + + /* + * ready: flag set by CGS initialization code once it's ready to + * start executing instructions in a potentially-secure + * guest + * + * The definition here is a bit fuzzy, because this is essentially + * part of a self-sanity-check, rather than a strict mechanism. + * + * It's not feasible to have a single point in the common machine + * init path to configure confidential guest support, because + * different mechanisms have different interdependencies requiring + * initialization in different places, often in arch or machine + * type specific code. It's also usually not possible to check + * for invalid configurations until that initialization code. + * That means it would be very easy to have a bug allowing CGS + * init to be bypassed entirely in certain configurations. + * + * Silently ignoring a requested security feature would be bad, so + * to avoid that we check late in init that this 'ready' flag is + * set if CGS was requested. If the CGS init hasn't happened, and + * so 'ready' is not set, we'll abort. + */ + bool ready; }; typedef struct ConfidentialGuestSupportClass { diff --git a/softmmu/vl.c b/softmmu/vl.c index 0d934844ff..9eb9dab1fc 100644 --- a/softmmu/vl.c +++ b/softmmu/vl.c @@ -101,6 +101,7 @@ #include "qemu/plugin.h" #include "qemu/queue.h" #include "sysemu/arch_init.h" +#include "exec/confidential-guest-support.h" #include "ui/qemu-spice.h" #include "qapi/string-input-visitor.h" @@ -2498,6 +2499,8 @@ static void qemu_create_cli_devices(void) static void qemu_machine_creation_done(void) { + MachineState *machine = MACHINE(qdev_get_machine()); + /* Did we create any drives that we failed to create a device for? */ drive_check_orphaned(); @@ -2517,6 +2520,13 @@ static void qemu_machine_creation_done(void) qdev_machine_creation_done(); + if (machine->cgs) { + /* + * Verify that Confidential Guest Support has actually been initialized + */ + assert(machine->cgs->ready); + } + if (foreach_device_config(DEV_GDB, gdbserver_start) < 0) { exit(1); } diff --git a/target/i386/sev.c b/target/i386/sev.c index 590cb31fa8..f9e9b5d8ae 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;