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".. 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? Thanks, -- Peter Xu