On 04/06/2026 20:05, Ackerley Tng wrote:
Suzuki K Poulose <[email protected]> writes:
[...snip...]
+In the case where ``type`` is KVM_SEV_SNP_PAGE_TYPE_ZERO, ``uaddr`` will be
+ignored completely. Otherwise, ``uaddr`` is required if
+kvm.vm_memory_attributes=1 and optional if kvm.vm_memory_attributes=0, since
+in the latter case guest memory can be initialized directly from userspace
+prior to converting it to private and passing the GPA range on to this
+interface.
Just to confirm, so the sev_gmem_prepare doesn't destroy the contents in
the process of making it "private" ? i.e., the contents of a SNP shared
page are preserved while transitioning to "SNP Private" (via RMP
update).
Suzuki
The following is the guest_memfd perspective, I didn't look at the SNP
spec:
Do you mean specifically for KVM_SEV_SNP_PAGE_TYPE_ZERO, or for any
type?
guest_memfd has no plans to do any special zeroing based on type.
guest_memfd decoupled zeroing from preparation a while ago (Michael had
some patches), so zeroing is supposed to be once during folio ownership
by guest_memfd, tracked by the uptodate flag, and preparation is tracked
outside of guest_memfd. So far only SNP does preparation.
I am talking about the SEV SNP conversions (specifically quoted in my
response), I will follow up on Michael's response.
Suzuki
