On 17.02.25 13:08, Paolo Bonzini wrote:
It is possible to start QEMU with a confidential-guest-support object even in TCG mode. While there is already a check in qemu_machine_creation_done:if (machine->cgs && !machine->cgs->ready) { error_setg(errp, "accelerator does not support confidential guest %s", object_get_typename(OBJECT(machine->cgs))); exit(1); } the creation of RAMBlocks happens earlier, in qemu_init_board(), if the command line does not override the default memory backend with -M memdev. Then the RAMBlock will try to use guest_memfd (because machine_require_guest_memfd correctly returns true; at least correctly according to the current implementation) and trigger the assertion failure for kvm_enabled(). This happend with a command line as simple as the following: 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. Cc: Xiaoyao Li <xiaoyao...@intel.com> Cc: qemu-sta...@nongnu.org Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- system/physmem.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/system/physmem.c b/system/physmem.c index 67c9db9daad..1ddf9fb10d0 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -1882,7 +1882,11 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) if (new_block->flags & RAM_GUEST_MEMFD) { int ret;- 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))); + goto out_free; + } assert(new_block->guest_memfd < 0);ret = ram_block_discard_require(true);
Reviewed-by: David Hildenbrand <da...@redhat.com> -- Cheers, David / dhildenb
