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Re: [Qemu-devel] [PATCH v3 11/29] vhost+postcopy: Transmit 'listen' to c
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH v3 11/29] vhost+postcopy: Transmit 'listen' to client |
Date: |
Wed, 7 Mar 2018 18:05:21 +0800 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Tue, Mar 06, 2018 at 11:20:56AM +0000, Dr. David Alan Gilbert wrote:
> * Peter Xu (address@hidden) wrote:
> > On Mon, Mar 05, 2018 at 05:42:42PM +0000, Dr. David Alan Gilbert wrote:
> > > * Peter Xu (address@hidden) wrote:
> > > > On Fri, Feb 16, 2018 at 01:16:07PM +0000, Dr. David Alan Gilbert (git)
> > > > wrote:
> > > >
> > > > [...]
> > > >
> > > > > typedef struct VuVirtqElement {
> > > > > diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> > > > > index 621543e654..bdec9ec0e8 100644
> > > > > --- a/docs/interop/vhost-user.txt
> > > > > +++ b/docs/interop/vhost-user.txt
> > > > > @@ -682,6 +682,12 @@ Master message types
> > > > > the slave must open a userfaultfd for later use.
> > > > > Note that at this stage the migration is still in precopy mode.
> > > > >
> > > > > + * VHOST_USER_POSTCOPY_LISTEN
> > > > > + Id: 27
> > > > > + Master payload: N/A
> > > > > +
> > > > > + Master advises slave that a transition to postcopy mode has
> > > > > happened.
> > > >
> > > > Could we add something to explain why this listen needs to be
> > > > broadcasted to clients? Since I failed to find it out quickly
> > > > myself. :(
> > >
> > > I've changed this to:
> > >
> > > * VHOST_USER_POSTCOPY_LISTEN
> > > Id: 29
> > > Master payload: N/A
> > >
> > > Master advises slave that a transition to postcopy mode has
> > > happened.
> > > The slave must ensure that shared memory is registered with
> > > userfaultfd
> > > to cause faulting of non-present pages.
> >
> > But shouldn't this be assured by the SET_MEM_TABLE call?
>
> Yes, it is the set_mem_table that does the register - but it only
> registers it with userfaultfd if it's received a 'listen' notification,
> otherwise it assumes it's a normal precopy migration.
I think I got the picture now. Please add this after the enhanced
document:
Reviewed-by: Peter Xu <address@hidden>
Thanks,
--
Peter Xu