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

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Message-ID: <04d6d0cb-8e60-88a0-061e-62c7c70024c5@gmail.com>
Date:   Mon, 12 Nov 2018 16:52:37 -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>,
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        "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 4:40 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? 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.

One possible caveat is if __va() and __phys_to_virt() behave differently
(e.g: because of CONFIG_DEBUG_VIRTUAL or other things).
-- 
Florian