Sean Christopherson <[email protected]> writes: > On Fri, May 15, 2026, Ackerley Tng wrote: >> Sean Christopherson <[email protected]> writes: >> >> > >> > [...snip...] >> > >> >> +#ifdef CONFIG_USERFAULTFD >> >> +static bool kvm_gmem_can_userfault(struct vm_area_struct *vma, >> >> vm_flags_t vm_flags) >> >> +{ >> >> + struct inode *inode = file_inode(vma->vm_file); >> >> + >> >> + /* >> >> + * Only support userfaultfd for guest_memfd with INIT_SHARED flag. >> >> + * This ensures the memory can be mapped to userspace. >> >> + */ >> >> Is the principle here that any memory that is allowed to be mapped to >> userspace can be userfault-ed? > > Yes? It's more the opposite though: memory that can't be SHARED and thus > can't > be mapped into userspace can't possibly support userfaultfd. Six of one, half > dozen of the other, but I think it's important to highlight that there's no > judgment call being made, i.e. we aren't deciding to support only SHARED just > because we're lazy, it's a hard requirement.
I guess this series is only intended to support some kinds of UFFD, but IIUC technically UFFDIO_CONTINUE can be used after the private memory is inserted (e.g. for TDX live migration).
