From: Julien Grall <julien.grall@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Emil Velikov <emil.l.velikov@gmail.com>,
Russell King <linux@armlinux.org.uk>,
Denis Efremov <efremov@linux.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [Xen-devel] [PATCH] ARM: xen: unexport HYPERVISOR_platform_op function
Date: Tue, 1 Oct 2019 15:39:41 +0100 [thread overview]
Message-ID: <9e04485f-2d4a-81a2-c7e1-e50dd888930f@arm.com> (raw)
In-Reply-To: <20191001143334.GA46651@lakrids.cambridge.arm.com>
On 01/10/2019 15:33, Mark Rutland wrote:
> Hi Julien,
Hi Mark,
>
> On Sat, Sep 07, 2019 at 11:05:45AM +0100, Julien Grall wrote:
>> 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.
>
> I'm seeing this when building arm64 defconfig v5.4-rc1:
>
> | [mark@lakrids:~/src/linux]% usekorg 8.1.0 make ARCH=arm64 CROSS_COMPILE=aarch64-linux- -j56 -s
> | arch/arm64/Makefile:62: CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will not be built
> | WARNING: "HYPERVISOR_platform_op" [vmlinux] is a static EXPORT_SYMBOL_GPL
> | WARNING: "HYPERVISOR_platform_op" [vmlinux] is a static EXPORT_SYMBOL_GPL
>
> I couldn't see a follow-up; do you have a patch for this?
The first e-mail of the thread should contain a patch to address the warning
(see [1]). But it is still waiting on an Ack from Stefano so it can get merged.
Cheers,
[1] https://patchwork.kernel.org/patch/11135601/
--
Julien Grall
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next prev parent reply other threads:[~2019-10-01 14:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-06 15:39 [PATCH] ARM: xen: unexport HYPERVISOR_platform_op function Arnd Bergmann
2019-09-06 15:55 ` [Xen-devel] " Andrew Cooper
2019-09-06 15:59 ` Jan Beulich
2019-09-06 16:00 ` Arnd Bergmann
2019-09-06 17:20 ` Andrew Cooper
2019-09-07 10:05 ` Julien Grall
2019-10-01 14:33 ` Mark Rutland
2019-10-01 14:39 ` Julien Grall [this message]
2019-10-01 14:46 ` Mark Rutland
2019-10-01 17:38 ` Stefano Stabellini
2019-10-01 18:57 ` Arnd Bergmann
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