Re: [PATCH v7 08/13] confidential guest support: Move SEV initialization into arch specific code

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 14 Jan 2021 10:58:06 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> 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@gibson.dropbear.id.au>
> ---
>  accel/kvm/kvm-all.c   | 14 --------------
>  accel/kvm/sev-stub.c  |  4 ++--
>  target/i386/kvm/kvm.c | 12 ++++++++++++
>  target/i386/sev.c     |  7 ++++++-
>  4 files changed, 20 insertions(+), 17 deletions(-)
> 

(...)

> @@ -2135,6 +2136,17 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      uint64_t shadow_mem;
>      int ret;
>      struct utsname utsname;
> +    Error *local_err = NULL;
> +
> +    /*
> +     * if memory encryption object is specified then initialize the
> +     * memory encryption context (no-op otherwise)
> +     */
> +    ret = sev_kvm_init(ms->cgs, &local_err);

Maybe still leave a comment here, as the code will still need to be
modified to handle non-SEV x86 mechanisms?

> +    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 3d94635397..aa79cacabe 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);

This looks a bit ugly; maybe we want the generic code to generate a
separate version of the cast macro that doesn't assert? Just cosmetics,
though.

>      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__);

Reviewed-by: Cornelia Huck <cohuck@redhat.com>