From: Peter Xu <peterx@redhat.com>
To: lma <lma@suse.de>
Cc: qemu-devel@nongnu.org, dgilbert@redhat.com, quintela@redhat.com
Subject: Re: [PATCH 0/3] Postcopy migration: Add userfaultfd- user-mode-only capability
Date: Fri, 15 Oct 2021 14:12:42 +0800 [thread overview]
Message-ID: <YWkb2rrrkMLC8BwM@t490s> (raw)
In-Reply-To: <7c0161fab24b06fa249061780a7f30d4@suse.de>
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
next prev parent reply other threads:[~2021-10-15 6:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-14 9:15 [PATCH 0/3] Postcopy migration: Add userfaultfd- user-mode-only capability Lin Ma
2021-10-14 9:15 ` [PATCH 1/3] migration: introduce postcopy-uffd-usermode-only capability Lin Ma
2021-10-14 9:15 ` [PATCH 2/3] migration: postcopy-uffd-usermode-only documentation Lin Ma
2021-10-14 9:15 ` [PATCH 3/3] tests: add postcopy-uffd-usermode-only capability into migration-test Lin Ma
2021-10-14 23:43 ` [PATCH 0/3] Postcopy migration: Add userfaultfd- user-mode-only capability Peter Xu
2021-10-15 5:38 ` lma
2021-10-15 6:12 ` Peter Xu [this message]
2021-10-15 8:16 ` lma
2021-10-15 8:28 ` Peter Xu
2021-10-15 9:49 ` lma
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