Re: [PATCH v4 04/14] confidential guest support: introduce ConfidentialGuestMemoryEncryptionOps for encrypted VMs

[Dov Murik]

On 04/08/2021 14:55, Ashish Kalra wrote:
> From: Brijesh Singh <brijesh.singh@amd.com>
> 
> When memory encryption is enabled in VM, the guest RAM will be encrypted
> with the guest-specific key, to protect the confidentiality of data while
> in transit we need to platform specific hooks to save or migrate the
> guest RAM.
> 
> Introduce the new ConfidentialGuestMemoryEncryptionOps in this patch
> which will be later used by the encrypted guest for migration.

Do we already have SEV / ConfidentialGuest debug operations? (for
reading SEV guest memory from gdb if debug is allowed in policy)

Are they supposed to be in the same Ops struct? Another?


> 
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
>  include/exec/confidential-guest-support.h | 27 +++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/include/exec/confidential-guest-support.h 
> b/include/exec/confidential-guest-support.h
> index ba2dd4b5df..d8b4bd4c42 100644
> --- a/include/exec/confidential-guest-support.h
> +++ b/include/exec/confidential-guest-support.h
> @@ -20,6 +20,7 @@
> 
>  #ifndef CONFIG_USER_ONLY
> 
> +#include <qapi/qapi-types-migration.h>
>  #include "qom/object.h"
> 
>  #define TYPE_CONFIDENTIAL_GUEST_SUPPORT "confidential-guest-support"
> @@ -53,8 +54,34 @@ struct ConfidentialGuestSupport {
>      bool ready;
>  };
> 
> +/**
> + * The functions registers with ConfidentialGuestMemoryEncryptionOps will be
> + * used during the encrypted guest migration.
> + */
> +struct ConfidentialGuestMemoryEncryptionOps {

[style] in QEMU you should add a 'typedef' at the beginning and call the
type ConfidentialGuestMemoryEncryptionOps, and then you don't use the
keyword 'struct' when you refer to it.  See for example the definition
of ConfidentialGuestSupportClass below.


> +    /* Initialize the platform specific state before starting the migration 
> */
> +    int (*save_setup)(MigrationParameters *p);
> +
> +    /* Write the encrypted page and metadata associated with it */
> +    int (*save_outgoing_page)(QEMUFile *f, uint8_t *ptr, uint32_t size,
> +                              uint64_t *bytes_sent);
> +
> +    /* Load the incoming encrypted page into guest memory */
> +    int (*load_incoming_page)(QEMUFile *f, uint8_t *ptr);
> +
> +    /* Check if gfn is in shared/unencrypted region */
> +    bool (*is_gfn_in_unshared_region)(unsigned long gfn);

The comment says "shared/unencrypted", but the function name talks about
"unshared".  I prefer:

    /* Check if gfn is in encrypted region */
    bool (*is_gfn_in_encrypted_region)(unsigned long gfn);

(and then maybe the comment is useless?)


> +
> +    /* Write the shared regions list */
> +    int (*save_outgoing_shared_regions_list)(QEMUFile *f);
> +
> +    /* Load the shared regions list */
> +    int (*load_incoming_shared_regions_list)(QEMUFile *f);
> +};
> +
>  typedef struct ConfidentialGuestSupportClass {
>      ObjectClass parent;
> +    struct ConfidentialGuestMemoryEncryptionOps *memory_encryption_ops;

per above, remove 'struct'.


>  } ConfidentialGuestSupportClass;
> 
>  #endif /* !CONFIG_USER_ONLY */
>