On Mon, Feb 17, 2025 at 1:28 PM Philippe Mathieu-Daudé <[email protected]>
wrote:
> qemu-system-x86_64 -m 512 -nographic -object
sev-snp-guest,reduced-phys-bits=48,id=sev0 \
> -M q35,kernel-irqchip=split,confidential-guest-support=sev0
> qemu-system-x86_64: ../system/physmem.c:1871: ram_block_add: Assertion
`kvm_enabled()' failed.
I'd expect sev-snp-guest to bail out early enough.
Is a KVM-enabled check in sev_snp_guest_instance_init() missing?
instance_init cannot do any check (it cannot fail). There is a check for
whether sev_common_kvm_init succeeded:
if (machine->cgs && !machine->cgs->ready) {
error_setg(errp, "accelerator does not support confidential guest %s",
object_get_typename(OBJECT(machine->cgs)));
exit(1);
}
but that doesn't help if the system/physmem.c code is reached before
qemu_machine_creation_done(), for example in qemu_init_board().
Likewise, you cannot fal in host_memory_backend_init() because that's
also an instance_init callback.
> - assert(kvm_enabled());
> + if (!kvm_enabled()) {
> + error_setg(errp, "cannot set up private guest memory for %s: KVM
required",
> + object_get_typename(OBJECT(current_machine->cgs)));
Common code should be SW vs HW accel, so IMHO your check
should go within sev_snp_guest_instance_init(), removing
the assertion here. That said I have no clue about SEV.
This code is outside accel/kvm or target/*/kvn, but it is not quite
common code. A few lines below you have:
new_block->guest_memfd =
kvm_create_guest_memfd(new_block->max_length, 0, errp);
Paolo
