On 11/14/2025 5:25 AM, Peter Xu wrote:
On Fri, Oct 24, 2025 at 05:17:20PM +0800, Xiaoyao Li wrote:
On 10/24/2025 2:59 AM, Peter Xu wrote:
This name is too generic, and can conflict with in-place guest-memfd
support. Add a _PRIVATE suffix to show what it really means: it is always
silently using an internal guest-memfd to back a shared host backend,
rather than used in-place.
This paves way for in-place guest-memfd, which means we can have a ramblock
that allocates pages completely from guest-memfd (private or shared).
It's for patch 4-7. Regarding the rename. How about:
- RAM_GUEST_MEMFD => RAM_PRIVATE_MEMORY
- backend->guest_memfd => backend->private_memory
- machine_require_guest_memfd() => machine_require_private_memory()
- cgs->require_guest_memfd => cgs->require_private_memory
For CoCo VMs, what they require is the support of private memory, while the
guest_memfd is how linux provides private memory support. But with mmap
support added to guest memfd, it can serve as shared/non-private memory as
well. Futher, in the future when in-place conversion support is implemented,
a single guest memfd can serve as both shared and private in different
parts. So guest_memfd_private will be confusing at that time.
That's more or less a valid point.
Said so, I think PRIVATE_MEMORY is confusing too v.s. RAM_PRIVATE. See:
commit 6169f1193657d0ba630a2ce33cef639ae918bce4
Author: Steve Sistare <[email protected]>
Date: Wed Jan 15 11:00:31 2025 -0800
memory: add RAM_PRIVATE
Not to mention its possible confusion against mmap(MAP_PRIVATE) which is
even more well known (where here RAM_PRIVATE is exactly about it).
It'll not be a concern until private gmemfd will start to back shared
memories, even if it happens (I believe it will, a matter of time..) IMHO
it's still fine to use guest_memfd_private, because here private describes
that the fd is a private FD (not the memory is private). It's private
because it's hidden inside each ramblock that matters. Then a fd that is
private can still back shared memories.
Would you mind I keep everything as-is for now?
I'm fine.
Thanks,
