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

David Gibson
2021-01-18T03:05:35Z

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On Fri, Jan 15, 2021 at 02:24:25PM +0100, Cornelia Huck wrote:
> 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?

Uh.. I'm confused.. this hunk is adding a comment, not removing one..

>
> > + 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.

I tend to the view that the clunkiness of this textually is
outweighted by using object_dynamic_cast() which has well known
semantics, rather than requiring someone reading the code to
understand another intermediate macro.

> > 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>
>

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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