linux-kernel - Re: [PATCH v3 4/6] arm64: Utilize phys_initrd_start/phys_initrd

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Date:   Mon, 5 Nov 2018 12:51:23 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        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,
        Russell King <linux@...linux.org.uk>, green.hu@...il.com,
        deanbo422@...il.com, gxt@....edu.cn,
        linux-snps-arc@...ts.infradead.org, vgupta@...opsys.com
Subject: Re: [PATCH v3 4/6] arm64: Utilize phys_initrd_start/phys_initrd_size

On 11/5/18 12:44 PM, Ard Biesheuvel wrote:
> On 5 November 2018 at 21:41, Florian Fainelli <f.fainelli@...il.com> wrote:
>> On 11/5/18 12:39 PM, Ard Biesheuvel wrote:
>>> Hi Florian,
>>>
>>> On 31 October 2018 at 20:28, Florian Fainelli <f.fainelli@...il.com> wrote:
>>>> ARM64 is the only architecture that re-defines
>>>> __early_init_dt_declare_initrd() in order for that function to populate
>>>> initrd_start/initrd_end with physical addresses instead of virtual
>>>> addresses. Instead of having an override we can leverage
>>>> drivers/of/fdt.c populating phys_initrd_start/phys_initrd_size to
>>>> populate those variables for us.
>>>>
>>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>>> ---
>>>>  arch/arm64/mm/init.c | 19 +++++++++----------
>>>>  1 file changed, 9 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>>>> index 3cf87341859f..00ef2166bb73 100644
>>>> --- a/arch/arm64/mm/init.c
>>>> +++ b/arch/arm64/mm/init.c
>>>> @@ -72,8 +72,8 @@ static int __init early_initrd(char *p)
>>>>         if (*endp == ',') {
>>>>                 size = memparse(endp + 1, NULL);
>>>>
>>>> -               initrd_start = start;
>>>> -               initrd_end = start + size;
>>>> +               phys_initrd_start = start;
>>>> +               phys_initrd_size = size;
>>>>         }
>>>>         return 0;
>>>>  }
>>>> @@ -408,14 +408,14 @@ void __init arm64_memblock_init(void)
>>>>                 memblock_add(__pa_symbol(_text), (u64)(_end - _text));
>>>>         }
>>>>
>>>> -       if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_start) {
>>>> +       if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
>>>>                 /*
>>>>                  * Add back the memory we just removed if it results in the
>>>>                  * initrd to become inaccessible via the linear mapping.
>>>>                  * Otherwise, this is a no-op
>>>>                  */
>>>> -               u64 base = initrd_start & PAGE_MASK;
>>>> -               u64 size = PAGE_ALIGN(initrd_end) - base;
>>>> +               u64 base = phys_initrd_start & PAGE_MASK;
>>>> +               u64 size = PAGE_ALIGN(phys_initrd_size);
>>>>
>>>>                 /*
>>>>                  * We can only add back the initrd memory if we don't end up
>>>> @@ -460,12 +460,11 @@ void __init arm64_memblock_init(void)
>>>>          */
>>>>         memblock_reserve(__pa_symbol(_text), _end - _text);
>>>>  #ifdef CONFIG_BLK_DEV_INITRD
>>>> -       if (initrd_start) {
>>>> -               memblock_reserve(initrd_start, initrd_end - initrd_start);
>>>> -
>>>> +       if (phys_initrd_size) {
>>>>                 /* the generic initrd code expects virtual addresses */
>>>> -               initrd_start = __phys_to_virt(initrd_start);
>>>> -               initrd_end = __phys_to_virt(initrd_end);
>>>> +               initrd_start = __phys_to_virt(phys_initrd_start);
>>>> +               initrd_end = initrd_start + phys_initrd_size;
>>>> +               initrd_below_start_ok = 0;
>>>
>>> Where is this assignment coming from?
>>
>> __early_init_dt_declare_initrd() sets initrd_below_start_ok to 1 though
>> after patch #5 this is not necessary any more.
> 
> Yes, but why? The original arm64 version of
> __early_init_dt_declare_initrd() does not set it but now you set to 1
> in the IS_ENABLED(CONFIG_ARM64) section in the generic code and set it
> back to 0 here.

Humm, it is an if (!IS_ENABLED(CONFIG_ARM64)) condition, so we would not
be taking that branch on an ARM64 kernel.

If you are saying the assignment is not necessary anymore after patch #5
, that is true, though this can only be done a part of part #5, not as
part of patch #4 in order not to break initrd functionality in-between
patches.

> 
> Or am I missing something?
> 

Not sure, I could be too, it's Monday after all :)
-- 
Florian