Re: [PATCH v15 11/23] KVM: selftests: Set shared attributes for ucall guest_memfd pages

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 10/2/2026 3:37 AM, Lisa Wang wrote:
> The default attributes for guest_memfd pages without in-place conversion
> is private. 

This is wrong. The default memory attribute is of a @gfn is shared without
in-place conversion, i.e., with per-vm memory attribute.

We don't need this patch actually. And I have tested with reverting this patch,
with both out of place conversion and in-place conversion. Both worked.

> However, the ucall pages need to be shared between the host
> and the guest. Thus, set them as shared.
> 
> Signed-off-by: Lisa Wang <wyihan@google.com>
> ---
>  tools/testing/selftests/kvm/lib/ucall_common.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
> index 029ce21f9f2f..c03dfc763172 100644
> --- a/tools/testing/selftests/kvm/lib/ucall_common.c
> +++ b/tools/testing/selftests/kvm/lib/ucall_common.c
> @@ -27,6 +27,7 @@ static struct ucall_header *ucall_pool;
>  
>  void ucall_init(struct kvm_vm *vm, gpa_t mmio_gpa)
>  {
> +	struct userspace_mem_region *region;
>  	struct ucall_header *hdr;
>  	struct ucall *uc;
>  	gva_t gva;
> @@ -37,6 +38,13 @@ void ucall_init(struct kvm_vm *vm, gpa_t mmio_gpa)
>  	hdr = (struct ucall_header *)addr_gva2hva(vm, gva);
>  	memset(hdr, 0, sizeof(*hdr));
>  
> +	region = vm_get_mem_region(vm, MEM_REGION_DATA);
> +	if (region->region.flags & KVM_MEM_GUEST_MEMFD) {
> +		size_t aligned_sz = align_up(sizeof(*hdr), vm->page_size);
> +
> +		vm_mem_set_shared(vm, addr_gva2gpa(vm, gva), aligned_sz);
> +	}
> +
>  	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
>  		uc = &hdr->ucalls[i];
>  		uc->hva = uc;
>