linux-kernel - Re: [PATCH] xen: avoid link error on ARM

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Date:   Tue, 5 Mar 2019 07:39:15 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>,
        Matthew Wilcox <willy@...radead.org>,
        Paul Durrant <paul.durrant@...rix.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Subject: Re: [PATCH] xen: avoid link error on ARM

On 04/03/2019 21:47, Arnd Bergmann wrote:
> Building the privcmd code as a loadable module on ARM, we get
> a link error due to the private cache management functions:
> 
> ERROR: "__sync_icache_dcache" [drivers/xen/xen-privcmd.ko] undefined!
> 
> Move the code into a new file that is built along with privcmd.o
> but is always built-in, even when the latter is a loadable module.
> 
> xen_remap_vma_range() may not be the best name here, if someone
> comes up with a better one, let me know.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/xen/Makefile  |  3 +++
>  drivers/xen/mm.c      | 41 +++++++++++++++++++++++++++++++++++++++++
>  drivers/xen/privcmd.c | 30 +-----------------------------
>  include/xen/xen-ops.h |  3 +++
>  4 files changed, 48 insertions(+), 29 deletions(-)
>  create mode 100644 drivers/xen/mm.c
> 
> diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> index ad3844d9f876..7124f9e749b4 100644
> --- a/drivers/xen/Makefile
> +++ b/drivers/xen/Makefile
> @@ -29,6 +29,9 @@ obj-$(CONFIG_SWIOTLB_XEN)		+= swiotlb-xen.o
>  obj-$(CONFIG_XEN_MCE_LOG)		+= mcelog.o
>  obj-$(CONFIG_XEN_PCIDEV_BACKEND)	+= xen-pciback/
>  obj-$(CONFIG_XEN_PRIVCMD)		+= xen-privcmd.o
> +ifdef CONFIG_XEN_PRIVCMD
> +obj-y					+= mm.o
> +endif

Can we avoid that ifdef in the Makefile?

I'd rather have an architecture independant builtin driver added which
is always included for CONFIG_XEN. This would allow to move redundant
stuff from arch/*/xen/ into it (e.g. xen_vcpu_id).

So: rename mm.c to xen-builtin.c, use:

obj-$(CONFIG_XEN) += xen-builtin.o


Juergen