Re: [PATCH v13 13/22] KVM: selftests: Set first memory region as shared if guest_memfd

[Xiaoyao Li]

On 7/1/2026 2:18 AM, Ackerley Tng wrote:
> > > I think this patch should fully buy into in-place conversions, so we
> > > need to also set GUEST_MEMFD_FLAG_MMAP:
> > >
> > > @@ -483,6 +483,7 @@ struct kvm_vm *__vm_create(struct vm_shape shape,
> > > u32 nr_runnable_vcpus,
> > >    {
> > >    	u64 nr_pages = vm_nr_pages_required(shape.mode, nr_runnable_vcpus,
> > >    						 nr_extra_pages);
> > > +	enum vm_mem_backing_src_type src_type = VM_MEM_SRC_ANONYMOUS;
> > >    	struct userspace_mem_region *slot0;
> > >    	u64 gmem_flags = 0;
> > >    	struct kvm_vm *vm;
> > > @@ -503,10 +504,16 @@ struct kvm_vm *__vm_create(struct vm_shape
> > > shape, u32 nr_runnable_vcpus,
> > >    	 */
> > >    	if (is_guest_memfd_required(shape)) {
> > >    		flags |= KVM_MEM_GUEST_MEMFD;
> > > -		gmem_flags |= GUEST_MEMFD_FLAG_INIT_SHARED;
> > > +		gmem_flags |= GUEST_MEMFD_FLAG_INIT_SHARED | GUEST_MEMFD_FLAG_MMAP;
> > GUEST_MEMFD_FLAG_INIT_SHARED is valid only when the memory attributes is
> > per-gmem.
> GUEST_MEMFD_FLAG_INIT_SHARED was introduced before guest_memfd in-place
> conversions, so I think it's orthogonal to whether memory attributes is
> per-gmem.

But before gmem in-place conversion, i.e., per-gmem attribute, 
GUEST_MEMFD_FLAG_INIT_SHARED is not supported/valid for Coco VMs.
> > we need to check KVM_CAP_GUEST_MEMFD_FLAGS or kvm_has_gmem_attributes.
> I think we do want to deprecate the non-in-place-conversions setup, so
> how about inserting a TEST_REQIRE(kvm_has_gmem_attributes) here?

Well, then all the TDX and SNP selftest will be skipped on the kernel 
with gmem_in_place_conversion=false.

I don't object it. But we still need to get Sean's answer.