Re: [RFC PATCH 08/16] target/arm/kvm-rme: Populate the realm with boot images

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

On Fri, Jan 27, 2023 at 01:54:23PM -1000, Richard Henderson wrote:
> >   static void rme_vm_state_change(void *opaque, bool running, RunState state)
> >   {
> >       int ret;
> > @@ -72,6 +115,9 @@ static void rme_vm_state_change(void *opaque, bool running, RunState state)
> >           }
> >       }
> > +    g_slist_foreach(rme_images, rme_populate_realm, NULL);
> > +    g_slist_free_full(g_steal_pointer(&rme_images), g_free);
> 
> I suppose this technically works because you clear the list, and thus the
> hook is called only on the first transition to RUNNING.  On all subsequent
> transitions the list is empty.
> 
> I see that i386 sev does this immediately during machine init, alongside the
> kernel setup.  Since kvm_init has already been called, that seems workable,
> rather than queuing anything for later.

The problem I faced was that RME_POPULATE_REALM needs to be called after
rom_reset(), which copies all the blobs into guest memory, and that
happens at device reset time, after machine init and
kvm_cpu_synchronize_post_init().

> But I think ideally this would be handled generically in (approximately)
> kvm_cpu_synchronize_post_init, looping over all blobs.  This would handle
> any usage of '-device loader,...', instead of the 4 specific things you
> handle in the next patch.

I'd definitely prefer something generic that hooks into the loader, I'll
look into that. I didn't do it right away because the arm64 Linux kernel
loading is special, requires reserving extra RAM in addition to the blob
(hence the two parameters to kvm_arm_rme_add_blob()). But we could just
have a special case for the extra memory needed by Linux and make the rest
generic.

Thanks,
Jean