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Subject: Re: [PATCH v6 1/1] xen/time: do not decrease steal time after live
 migration on xen
To:     Dongli Zhang <dongli.zhang@oracle.com>,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
References: <1509500793-9896-1-git-send-email-dongli.zhang@oracle.com>
 <cb9986c7-2b30-5d43-946e-400e5efc41b2@oracle.com>
 <f2812a77-3df0-d6e8-8846-ebcca9d48909@oracle.com>
Cc:     jgross@suse.com, joao.m.martins@oracle.com
From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <95598986-2888-2784-8737-0aaa6991c728@oracle.com>
Date:   Thu, 2 Nov 2017 16:28:31 -0400
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On 11/01/2017 09:19 PM, Dongli Zhang wrote:
> Hi Boris,
>
> I have received from lkp@intel.com that the prior version of patch hit issue
> during compilation with aarch64-linux-gnu-gcc. I think this patch reviewed by
> you would hit the same compiling issue on arm64 (there is no issue with x86_64).
>
> -------------------------------------------------------------
>
> 1st issue:
>
> Without including header <linux/slab.h> into driver/xen/time.c, compilation on
> x86_64 works well (without any warning or error) but arm64 would hit the
> following error:
>
> drivers/xen/time.c: In function �xen_manage_runstate_time�:
> drivers/xen/time.c:94:20: error: implicit declaration of function
> �kmalloc_array� [-Werror=implicit-function-declaration]
>    runstate_delta = kmalloc_array(num_possible_cpus(),
>                     ^
>
> drivers/xen/time.c:131:3: error: implicit declaration of function �kfree�
> [-Werror=implicit-function-declaration]
>    kfree(runstate_delta);
>    ^
> cc1: some warnings being treated as errors
>
> About the 1st issue, should I submit a new patch including <linux/slab.h> or
> just a incremental based on previous patch merged into your own branch
> /tree?
>
> -------------------------------------------------------------
>
> 2nd issue:
>
> aarch64-linux-gnu-gcc expects a cast for kmalloc_array(). Is this really
> necessary as I did find people casting the return type of
> kmalloc/kcalloc/kmalloc_array in linux source code (e.g.,
> drivers/block/virtio_blk.c). Can we just ignore this warning?
>
> drivers/xen/time.c:94:18: warning: assignment makes pointer from integer without
> a cast [-Wint-conversion]
>    runstate_delta = kmalloc_array(num_possible_cpus(),
>                   ^
> -------------------------------------------------------------

That's because you need to declare kmalloc_array(), otherwise the
compiler by default assumes that it returns an int. So including
linux/slab.h should take care of both warnings.

I can add it while committing.


-boris


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