在 2021-10-15 14:12，Peter Xu 写道：
On Fri, Oct 15, 2021 at 01:38:06PM +0800, lma wrote:
在 2021-10-15 07:43，Peter Xu 写道：
> On Thu, Oct 14, 2021 at 05:15:48PM +0800, Lin Ma wrote:
> > Since kernel v5.11, Unprivileged user (without SYS_CAP_PTRACE
> > capability)
> > must pass UFFD_USER_MODE_ONLY to userfaultd in case
> > unprivileged_userfaultfd
> > sysctl knob is 0.
> > Please refer to https://lwn.net/Articles/819834/ and the kernel
> > commits:
> > 37cd0575 userfaultfd: add UFFD_USER_MODE_ONLY
> > d0d4730a userfaultfd: add user-mode only option to
> > unprivileged_userfaultfd sysctl knob
> >
> > This patch set adds a migration capability to pass UFFD_USER_MODE_ONLY
> > for postcopy migration.
>
> Then it's at least no KVM, no vhost, am I right? Could I ask is there a
> real
> user behind this? Thanks,
Well, The "user-mode-only" has nothing to do with qemu's user-mode
emulation.
I didn't follow why you thought my question was about "user-mode
emulation"..
Sorry about the misunderstanding.
To ask in another way: after this new cap set, qemu will get a SIGBUS
and VM
will crash during postcopy migrating as long as either KVM or
vhost-kernel
faulted on any of the missing pages, am I right?
Oops...Yes, you're right. It indeed casues qemu crash on destination due
to
fault on missing pages.
This patch set and my thought about introducing this cap to qemu are
wrong.
Thanks,
Lin
