Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH] ARM: xen: unexport HYPERVISOR_platform_op function | From | Julien Grall <> | Date | Sat, 7 Sep 2019 11:05:45 +0100 |
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Hi Andrew,
On 9/6/19 6:20 PM, Andrew Cooper wrote: > On 06/09/2019 17:00, Arnd Bergmann wrote: >> On Fri, Sep 6, 2019 at 5:55 PM Andrew Cooper <andrew.cooper3@citrix.com> wrote: >>> On 06/09/2019 16:39, Arnd Bergmann wrote: >>>> HYPERVISOR_platform_op() is an inline function and should not >>>> be exported. Since commit 15bfc2348d54 ("modpost: check for >>>> static EXPORT_SYMBOL* functions"), this causes a warning: >>>> >>>> WARNING: "HYPERVISOR_platform_op" [vmlinux] is a static EXPORT_SYMBOL_GPL >>>> >>>> Remove the extraneous export. >>>> >>>> Fixes: 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions") >>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de> >>> Something is wonky. That symbol is (/ really ought to be) in the >>> hypercall page and most definitely not inline. >>> >>> Which tree is that changeset from? I can't find the SHA. >> This is from linux-next, I think from the kbuild tree. > > Thanks. > > Julien/Stefano: Why are any of these hypercalls out-of-line? ARM > doesn't use the hypercall page, and there is no argument translation > (not even in arm32 as there are no 5-argument hypercalls declared).
I am not sure how the hypercall page makes things different. You still have to store the arguments in the correct register so...
> > They'd surely be easier to implement with a few static inlines and some > common code, than to try and replicate the x86 side hypercall_page > interface ?
... I don't think they will be easier to implement with a few static inlines. The implementation will likely end up to be similar to arch/x86/asm/xen/hypercall.h.
Furthermore, one of the downside of per-arch static inline is it is more difficult to ensure the prototype match for all the architectures. Although, it might be possible to make them common by only requesting per-arch to implement HYPERCALL_N(...).
So I think the code is better as it is.
While looking at the code, I also realized that the implementation of HYPERCALL_dm_op might be incorrect for Arm32. Similarly do privcmd call, I think dm_op call should enable user access as they will be used by userspace.
We don't use dm_op on Arm so far, hence why I think this was unnoticed. I will see if I can reproduce it and send a patch.
Cheers,
-- Julien Grall
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