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Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property |
Date: |
Tue, 28 Aug 2018 18:54:40 +0200 |
Hi
On Tue, Aug 28, 2018 at 6:49 PM Igor Mammedov <address@hidden> wrote:
>
> On Tue, 28 Aug 2018 17:38:40 +0200
> Marc-André Lureau <address@hidden> wrote:
>
> > The share=on/off property is used to modified mmap() MAP_SHARED
> > setting. Make it on by default for convenience and compatibility
> > reasons.
> it would be nice to state reasons here.
>
> also flipping default to on is behavioral change when
> used with bind policy which could make backend initialization fail
> so CLI that used to work (if there are any users of this without shared=on)
> won't work anymore.
memfd backend is passing shared=true to memory_region_init_ram_from_fd().
The patch allows to tweak that (instead of ignoring the property),
while keeping the value to shared=true.
>
> >
> > Signed-off-by: Marc-André Lureau <address@hidden>
> > ---
> > backends/hostmem-memfd.c | 4 +++-
> > qemu-options.hx | 4 +++-
> > 2 files changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
> > index 1e20fe0ba8..abd52364db 100644
> > --- a/backends/hostmem-memfd.c
> > +++ b/backends/hostmem-memfd.c
> > @@ -59,7 +59,8 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend,
> > Error **errp)
> >
> > name = object_get_canonical_path(OBJECT(backend));
> > memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
> > - name, backend->size, true, fd, errp);
> > + name, backend->size,
> > + backend->share, fd, errp);
> > g_free(name);
> > }
> >
> > @@ -131,6 +132,7 @@ memfd_backend_instance_init(Object *obj)
> >
> > /* default to sealed file */
> > m->seal = true;
> > + MEMORY_BACKEND(m)->share = true;
> > }
> >
> > static void
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index f14e423b7c..25c02d72b8 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -4029,7 +4029,7 @@ Memory backend objects offer more control than the
> > @option{-m} option that is
> > traditionally used to define guest RAM. Please refer to
> > @option{memory-backend-file} for a description of the options.
> >
> > address@hidden -object
> > memory-backend-memfd,address@hidden,address@hidden|off},address@hidden|off},address@hidden|off},address@hidden,address@hidden,address@hidden|preferred|bind|interleave},address@hidden|off},address@hidden|off},address@hidden
> > address@hidden -object
> > memory-backend-memfd,address@hidden,address@hidden|off},address@hidden|off},address@hidden|off},address@hidden|off},address@hidden,address@hidden,address@hidden|preferred|bind|interleave},address@hidden|off},address@hidden|off},address@hidden
> >
> > Creates an anonymous memory file backend object, which allows QEMU to
> > share the memory with an external process (e.g. when using
> > @@ -4051,6 +4051,8 @@ with the @option{seal} option (requires at least
> > Linux 4.16).
> > Please refer to @option{memory-backend-file} for a description of the
> > other options.
> >
> > +The @option{share} boolean option is @var{on} by default with memfd.
> > +
> > @item -object rng-random,address@hidden,address@hidden/dev/random}
> >
> > Creates a random number generator backend which obtains entropy from
>
>
--
Marc-André Lureau
- [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Marc-André Lureau, 2018/08/28
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Igor Mammedov, 2018/08/28
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property,
Marc-André Lureau <=
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Marc-André Lureau, 2018/08/28
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Igor Mammedov, 2018/08/29
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Marc-André Lureau, 2018/08/29
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Igor Mammedov, 2018/08/30
- Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Marc-André Lureau, 2018/08/30
Re: [Qemu-devel] [PATCH] hostmem-memfd: honour share=on/off property, Igor Mammedov, 2018/08/30