[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] xen/mem-reservation API and out-of-tree kernel modules
On 2/1/19 11:14 AM, Juergen Gross wrote: > On 01/02/2019 09:39, Oleksandr Andrushchenko wrote: >> On 1/31/19 11:44 PM, Stefano Stabellini wrote: >>> On Thu, 31 Jan 2019, Oleksandr Andrushchenko wrote: >>>> Hello, >>>> >>>> I am working on porting an out-of-tree kernel driver to the kernel >>>> 5.0 and that driver uses functionality provided by >>>> drivers/xen/mem-reservation.c >>>> module. Since commit [1] it is not possible to build a kernel module >>>> which uses mem-reservation API as xen_scrub_pages variable, which is >>>> checked in >>>> xenmem_reservation_scrub_page, became a kernel module parameter and is >>>> now only >>>> accessible for built-in modules: >>>> >>>> static inline void xenmem_reservation_scrub_page(struct page *page) >>>> ^^^^^^^^^^^^^ >>>> { >>>> if (xen_scrub_pages) >>>> ^^^^^^^^^^^^^^^ >>>> clear_highpage(page); >>>> } >>>> >>>> This results in link-time warning: >>>> >>>> WARNING: "xen_scrub_pages" [yourmodule.ko] undefined! >>>> >>>> and thus not allowing the module to run. At the moment I can only see a >>>> possible fix >>>> for this by making the following change: >>>> >>>> diff --git a/drivers/xen/mem-reservation.c b/drivers/xen/mem-reservation.c >>>> index 3782cf070338..85fecfec50e1 100644 >>>> --- a/drivers/xen/mem-reservation.c >>>> +++ b/drivers/xen/mem-reservation.c >>>> @@ -18,6 +18,7 @@ >>>> >>>> bool __read_mostly xen_scrub_pages = >>>> IS_ENABLED(CONFIG_XEN_SCRUB_PAGES_DEFAULT); >>>> core_param(xen_scrub_pages, xen_scrub_pages, bool, 0); >>>> +EXPORT_SYMBOL(xen_scrub_pages); >>>> >>>> but this looks a bit unusual for the kernel? >>>> >>>> I am looking for community advice here and help >>>> >>>> Thank you, >>>> Oleksandr >>>> >>>> [1] >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=197ecb3802c04499d8ff4f8cb28f6efa008067db >>> The alternative would be to turn xenmem_reservation_scrub_page into a >>> regular function (not a static inline)? >> Yes, it seems there is no other reasonable solution to this, but >> a regular function. I'll send a patch for that > What would you gain? This function would need to be exported. Yes, this is true, the function should be exported then > So its either the variable or the function. I am a bit confused with this because I'll have to export module parameter in this case, e.g. core_param(xen_scrub_pages, xen_scrub_pages, bool, 0); EXPORT_SYMBOL(xen_scrub_pages); which looks a bit unusual to me > > Juergen _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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