linux-kernel - Re: [PATCH v4 6/6] arch: Move initrd= parsing into do_mounts

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Date:   Thu, 15 Nov 2018 11:35:22 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vineet Gupta <vineet.gupta1@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Robin Murphy <robin.murphy@....com>,
        Laura Abbott <labbott@...hat.com>,
        Stefan Agner <stefan@...er.ch>,
        Johannes Weiner <hannes@...xchg.org>,
        Greg Hackmann <ghackmann@...roid.com>,
        Kristina Martsenko <kristina.martsenko@....com>,
        CHANDAN VN <chandan.vn@...sung.com>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>,
        "rppt@...ux.ibm.com" <rppt@...ux.ibm.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "green.hu@...il.com" <green.hu@...il.com>,
        "deanbo422@...il.com" <deanbo422@...il.com>,
        "gxt@....edu.cn" <gxt@....edu.cn>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH v4 6/6] arch: Move initrd= parsing into do_mounts_initrd.c

On 11/12/18 4:57 PM, Vineet Gupta wrote:
> On 11/12/18 4:52 PM, Florian Fainelli wrote:
>> On 11/12/18 4:40 PM, Vineet Gupta wrote:
>>> On 11/12/18 4:38 PM, Florian Fainelli wrote:
>>>>>>  #ifdef CONFIG_BLK_DEV_INITRD
>>>>>> -	if (initrd_start)
>>>>>> -		memblock_reserve(__pa(initrd_start), initrd_end - initrd_start);
>>>>>> +	if (phys_initrd_size) {
>>>>>> +		memblock_reserve(phys_initrd_start, phys_initrd_size);
>>>>>> +		initrd_start = (unsigned long)__va(phys_initrd_start);
>>>>>> +		initrd_end = initrd_start + phys_initrd_size;
>>>>>> +	}
>>>>>>  #endif
>>>>> The common code now uses phys_initrd*, and you also use the same in ARC code, do
>>>>> we still need the initrd_* setting here ?
>>>>> ARC semantics was using them as PA anyways.
>>>> Yes, the generic initrd code expects initrd_start/end to be virtual
>>>> addresses, which we now directly derive from phys_initrd_start, that
>>>> should really be equivalent.
>>> So we can skip this explicit setting above - ARC arch code doesn't access the virt
>>> initrd_start
>> OK, you are saying we could just have the generic initrd code do this
>> assignment instead of having each architecture do it, is that a correct
>> understanding? 
> 
> Correct !
> 
>> If so, I suppose it could be done, whether as of this
>> patch series or as a follow-up, either way is fine with me.
> 
> If it is not too much trouble, I'd prefer this now. I should have chimed earlier.
> 
>> One possible caveat is if __va() and __phys_to_virt() behave differently
>> (e.g: because of CONFIG_DEBUG_VIRTUAL or other things).
> 
> 
> Thing is, after your patches, we don't use the vanilla initrd_xxx in arch code any
> longer. So this becomes just an implementation detail, which core code may or
> maynot need and if it does, this needs to work already w/o having to set anything
> in arch code. Agree ?

If you do not mind, I would prefer this series to go in, as-is, and
clean up the initrd_start/initrd_end assignment as a follow up patch
series. The reason is mostly that I am not yet clear on the timing of
these operations between the architecture resolving the virtual address
and the initrd code starting to use it.

Would that sound reasonable to you?
-- 
Florian