linux-kernel - Re: [PATCH v2 1/2] kexec: Introduce "/sys/kernel/kexec_crash_low_size"

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Date:   Wed, 24 Aug 2016 19:37:09 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Dave Young <dyoung@...hat.com>, Yinghai Lu <yinghai@...nel.org>
Cc:     Baoquan He <bhe@...hat.com>, Xunlei Pang <xlpang@...hat.com>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH v2 1/2] kexec: Introduce
 "/sys/kernel/kexec_crash_low_size"

On 2016/08/24 at 16:20, Dave Young wrote:
> On 08/23/16 at 06:11pm, Yinghai Lu wrote:
>> On Wed, Aug 17, 2016 at 1:20 AM, Dave Young <dyoung@...hat.com> wrote:
>>> On 08/17/16 at 09:50am, Xunlei Pang wrote:
>>>> "/sys/kernel/kexec_crash_size" only handles crashk_res, it
>>>> is fine in most cases, but sometimes we have crashk_low_res.
>>>> For example, when "crashkernel=size[KMG],high" combined with
>>>> "crashkernel=size[KMG],low" is used for 64-bit x86.
>>>>
>>>> Like crashk_res, we introduce the corresponding sysfs file
>>>> "/sys/kernel/kexec_crash_low_size" for crashk_low_res.
>>>>
>>>> So, the exact total reserved memory is the sum of the two.
>>>>
>>>> crashk_low_res can also be shrunk via this new interface,
>>>> and users should be aware of what they are doing.
>> ...
>>>> @@ -218,6 +238,7 @@ static struct attribute * kernel_attrs[] = {
>>>>  #ifdef CONFIG_KEXEC_CORE
>>>>       &kexec_loaded_attr.attr,
>>>>       &kexec_crash_loaded_attr.attr,
>>>> +     &kexec_crash_low_size_attr.attr,
>>>>       &kexec_crash_size_attr.attr,
>>>>       &vmcoreinfo_attr.attr,
>>>>  #endif
>> would be better if you can use attribute_group .is_visible to control showing of
>> crash_low_size only when the crash_base is above 4G.
> I have same feeling that it looks odd to show low in sysfs in case no
> crashkernel=,high being used. Even if crashkernel=,high is used only in
> x86 the resource crashk_low is in common code. What do you think to move
> it to x86?

If want to put some restriction on it, I'd prefer to move crashk_low to arch x86, to make
it x86-specific.

We can show the interface unconditionally. If it isn't used, its size is 0, it doesn't matter.

Regards,
Xunlei

>
> Thanks
> Dave
>
>> Thanks
>>
>> Yinghai
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec

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