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    SubjectRe: [PATCH] xen/tmem: cleanup
    On Mon, Feb 06, 2012 at 04:49:42PM +0000, Jan Beulich wrote:
    > >>> On 06.02.12 at 17:37, Dan Magenheimer <dan.magenheimer@oracle.com> wrote:
    > >> From: Jan Beulich [mailto:JBeulich@suse.com]
    > >> Sent: Monday, February 06, 2012 1:13 AM
    > >> To: Dan Magenheimer
    > >> Cc: Jeremy Fitzhardinge; xen-devel@lists.xensource.com; Konrad Wilk;
    > > linux-kernel@vger.kernel.org
    > >> Subject: RE: [PATCH] xen/tmem: cleanup
    > >>
    > >> >>> On 04.02.12 at 17:42, Dan Magenheimer <dan.magenheimer@oracle.com> wrote:
    > >> >> From: Jan Beulich [mailto:JBeulich@suse.com]
    > >> >> Subject: [PATCH] xen/tmem: cleanup
    > >> >>
    > >> >> Use 'bool' for boolean variables. Do proper section placement.
    > >> >> Eliminate an unnecessary export.
    > >> >>
    > >> >> Signed-off-by: Jan Beulich <jbeulich@suse.com>
    > >> >> Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
    > >> >>
    > >> >> -int tmem_enabled __read_mostly;
    > >> >> -EXPORT_SYMBOL(tmem_enabled);
    > >> >> +bool __read_mostly tmem_enabled = false;
    > >> >
    > >> > tmem_enabled is used in xen/drivers/xen-selfballoon.c
    > >>
    > >> Which can't be built as a module, and hence the symbol doesn't need
    > >> exporting. This patch (of course, I'm tempted to say) survived build
    > >> testing.
    > >
    > > Yes, correct. BUT... I think only the reason xen-selfballoon.c
    > > can't be built as a module is because the MM variable vm_committed_as
    > > (or an access function) is not exported. Ideally xen-selfballoon.c
    > > probably should be a module but putting a core MM change in
    > > the critical path of a Xen-only-related enhancement seemed
    > > a recipe for sure failure.
    >
    > No, this isn't the main reason (as you say further down, this could
    > easily be adjusted for) afaict. The main reason is that
    > register_xen_selfballooning() is being called from non-modular
    > code (xen-balloon.c), which could be made a module too, but in
    > turn has at least one reference that wouldn't be nice to become
    > an export (balloon_set_new_target()).

    It would be nice if all of it could become modules. That way HVM
    device driver domains could load the whole thing without having much
    built-in code in the kernel.

    Is it possible to do that?
    >
    > Jan
    >
    > > Konrad, if you (1) disagree entirely, or (2) want to remove the
    > > tmem_enabled EXPORT_SYMBOL now and add it back later if/when
    > > the core MM change happens, I'll leave that up to you.
    > >
    > > If (2), the MM change should be added to the minor-tmem-related-
    > > changes-that-need-to-be-eventually-upstreamed list ;-)
    > >
    > > Dan
    >
    >
    >
    > --
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