diff mbox series

[v8,07/13] confidential guest support: Introduce cgs "ready" flag

Message ID 20210202041315.196530-8-david@gibson.dropbear.id.au (mailing list archive)
State New, archived
Headers show
Series Generalize memory encryption models | expand

Commit Message

David Gibson Feb. 2, 2021, 4:13 a.m. UTC
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 <david@gibson.dropbear.id.au>
---
 include/exec/confidential-guest-support.h | 24 +++++++++++++++++++++++
 softmmu/vl.c                              | 10 ++++++++++
 target/i386/sev.c                         |  2 ++
 3 files changed, 36 insertions(+)

Comments

Dr. David Alan Gilbert Feb. 3, 2021, 10:42 a.m. UTC | #1
* David Gibson (david@gibson.dropbear.id.au) wrote:
> 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 <david@gibson.dropbear.id.au>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  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..5dcf602047 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 fasible 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 1b464e3474..1869ed54a9 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"
> @@ -2497,6 +2498,8 @@ 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();
>  
> @@ -2516,6 +2519,13 @@ 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;
> -- 
> 2.29.2
>
Greg Kurz Feb. 3, 2021, 4:15 p.m. UTC | #2
On Tue,  2 Feb 2021 15:13:09 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> 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 <david@gibson.dropbear.id.au>
> ---
>  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..5dcf602047 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 fasible to have a single point in the common machine

s/fasible/feasible

Anyway,

Reviewed-by: Greg Kurz <groug@kaod.org>

> +     * 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 1b464e3474..1869ed54a9 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"
> @@ -2497,6 +2498,8 @@ 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();
>  
> @@ -2516,6 +2519,13 @@ 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;
David Gibson Feb. 4, 2021, 2:45 a.m. UTC | #3
On Wed, Feb 03, 2021 at 05:15:48PM +0100, Greg Kurz wrote:
> On Tue,  2 Feb 2021 15:13:09 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > 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 <david@gibson.dropbear.id.au>
> > ---
> >  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..5dcf602047 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 fasible to have a single point in the common machine
> 
> s/fasible/feasible

Fixed, thanks.

> 
> Anyway,
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>
> 
> > +     * 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 1b464e3474..1869ed54a9 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"
> > @@ -2497,6 +2498,8 @@ 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();
> >  
> > @@ -2516,6 +2519,13 @@ 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;
>
Venu Busireddy Feb. 10, 2021, 4:25 p.m. UTC | #4
On 2021-02-02 15:13:09 +1100, David Gibson wrote:
> 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 <david@gibson.dropbear.id.au>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Reviewed-by: Greg Kurz <groug@kaod.org>
> ---
>  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..5dcf602047 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 fasible to have a single point in the common machine

Just a nit pick.

s/fasible/feasible/

> +     * 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 1b464e3474..1869ed54a9 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"
> @@ -2497,6 +2498,8 @@ 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();
>  
> @@ -2516,6 +2519,13 @@ 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;
> -- 
> 2.29.2
David Gibson Feb. 11, 2021, 11:48 p.m. UTC | #5
On Wed, Feb 10, 2021 at 10:25:30AM -0600, Venu Busireddy wrote:
> On 2021-02-02 15:13:09 +1100, David Gibson wrote:
> > 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 <david@gibson.dropbear.id.au>
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > Reviewed-by: Greg Kurz <groug@kaod.org>
> > ---
> >  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..5dcf602047 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 fasible to have a single point in the common machine
> 
> Just a nit pick.
> 
> s/fasible/feasible/

Already fixed in the version that got merged.

> > +     * 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 1b464e3474..1869ed54a9 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"
> > @@ -2497,6 +2498,8 @@ 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();
> >  
> > @@ -2516,6 +2519,13 @@ 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;
>
diff mbox series

Patch

diff --git a/include/exec/confidential-guest-support.h b/include/exec/confidential-guest-support.h
index 3db6380e63..5dcf602047 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 fasible 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 1b464e3474..1869ed54a9 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"
@@ -2497,6 +2498,8 @@  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();
 
@@ -2516,6 +2519,13 @@  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;