Re: [PATCH 2/6] x86/mm: p2m_add_foreign() is HVM-only

[Oleksandr Tyshchenko <olekstysh@gmail.com>]

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Hello all.

[Sorry for the possible format issues]

On Tue, Dec 22, 2020 at 12:41 PM Andrew Cooper <andrew.cooper3@citrix.com>
wrote:

> On 21/12/2020 08:10, Jan Beulich wrote:
> > On 17.12.2020 20:18, Andrew Cooper wrote:
> >> On 15/12/2020 16:26, Jan Beulich wrote:
> >>> This is together with its only caller, xenmem_add_to_physmap_one().
> >> I can't parse this sentence.  Perhaps "... as is it's only caller," as a
> >> follow-on from the subject sentence.
> >>
> >>>  Move
> >>> the latter next to p2m_add_foreign(), allowing this one to become
> static
> >>> at the same time.
> >>>
> >>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> >> Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
> > So I had to ask Andrew to revert this (I was already at home when
> > noticing the breakage), as it turned out to break the shim build.
> > The problem is that xenmem_add_to_physmap() is non-static and
> > hence can't be eliminated altogether by the compiler when !HVM.
> > We could make the function conditionally static
> > "#if !defined(CONFIG_X86) && !defined(CONFIG_HVM)", but this
> > looks uglier to me than this extra hunk:
> >
> > --- unstable.orig/xen/common/memory.c
> > +++ unstable/xen/common/memory.c
> > @@ -788,7 +788,11 @@ int xenmem_add_to_physmap(struct domain
> >      union add_to_physmap_extra extra = {};
> >      struct page_info *pages[16];
> >
> > -    ASSERT(paging_mode_translate(d));
> > +    if ( !paging_mode_translate(d) )
> > +    {
> > +        ASSERT_UNREACHABLE();
> > +        return -EACCES;
> > +    }
> >
> >      if ( xatp->space == XENMAPSPACE_gmfn_foreign )
> >          extra.foreign_domid = DOMID_INVALID;
> >
> > Andrew, please let me know whether your ack stands with this (or
> > said alternative) added, or whether you'd prefer me to re-post.
>
> Yeah, this is probably neater than the ifdefary.  My ack stands.
>
> ~Andrew
>

I might miss something or did incorrect tests, but ...
... trying to build current staging
(7ba2ab495be54f608cb47440e1497b2795bd301a) for x86 (with # CONFIG_HVM is
not set) I got the following:

/media/b/build/build/tmp/work/x86_64-xt-linux/domd-image-weston/1.0-r0/repo/build/tmp/work/aarch64-poky-linux/xen/4.14.0+gitAUTOINC+2c6e5a8ceb-r0/git/xen/common/memory.c:941:
undefined reference to `xenmem_add_to_physmap_one'
/media/b/build/build/tmp/work/x86_64-xt-linux/domd-image-weston/1.0-r0/repo/build/tmp/work/aarch64-poky-linux/xen/4.14.0+gitAUTOINC+2c6e5a8ceb-r0/git/xen/common/memory.c:941:(.text+0x1e391):
relocation truncated to fit: R_X86_64_PC32 against undefined symbol
`xenmem_add_to_physmap_one'
ld:
/media/b/build/build/tmp/work/x86_64-xt-linux/domd-image-weston/1.0-r0/repo/build/tmp/work/aarch64-poky-linux/xen/4.14.0+gitAUTOINC+2c6e5a8ceb-r0/git/xen/.xen-syms.0:
hidden symbol `xenmem_add_to_physmap_one' isn't defined
ld: final link failed: Bad value

It is worth mentioning that I do not use pvshim_defconfig (I disable HVM
support via menuconfig manually before building).

-- 
Regards,

Oleksandr Tyshchenko

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