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Subject: Re: [PATCH] riscv: Drop setup_initrd
To:     Palmer Dabbelt <palmer@sifive.com>
Cc:     schwab@linux-m68k.org, aou@eecs.berkeley.edu,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
References: <mhng-fadb4889-1082-4cef-a4a6-8faf828c4528@palmer-si-x1c4>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <eee9cb69-6a3f-6a99-4e83-dbab3a8f5984@roeck-us.net>
Date:   Tue, 28 Aug 2018 17:36:28 -0700
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On 08/28/2018 05:09 PM, Palmer Dabbelt wrote:
> On Tue, 28 Aug 2018 15:12:38 PDT (-0700), linux@roeck-us.net wrote:
>> On Tue, Aug 28, 2018 at 03:03:00PM -0700, Palmer Dabbelt wrote:
>>> On Tue, 28 Aug 2018 14:59:59 PDT (-0700), linux@roeck-us.net wrote:
>>> >On Tue, Aug 28, 2018 at 11:46:09PM +0200, Andreas Schwab wrote:
>>> >>On Aug 28 2018, Guenter Roeck <linux@roeck-us.net> wrote:
>>> >>
>>> >>> On Tue, Aug 28, 2018 at 01:10:20PM -0700, Palmer Dabbelt wrote:
>>> >>>> On Thu, 09 Aug 2018 21:11:40 PDT (-0700), linux@roeck-us.net wrote:
>>> >>>> >setup_initrd() does not appear to serve a practical purpose other than
>>> >>>> >preventing qemu boots with "-initrd" parameter, so let's drop it.
>>> >>>> >
>>> >>>> >Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>>> >>>> >---
>>> >>>> > arch/riscv/kernel/setup.c | 39 ---------------------------------------
>>> >>>> > 1 file changed, 39 deletions(-)
>>> >>>> >
>>> >>>> >diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>>> >>>> >index 2e56af3281f8..579f58a42974 100644
>>> >>>> >--- a/arch/riscv/kernel/setup.c
>>> >>>> >+++ b/arch/riscv/kernel/setup.c
>>> >>>> >@@ -82,41 +82,6 @@ EXPORT_SYMBOL(empty_zero_page);
>>> >>>> > /* The lucky hart to first increment this variable will boot the other cores */
>>> >>>> > atomic_t hart_lottery;
>>> >>>> >
>>> >>>> >-#ifdef CONFIG_BLK_DEV_INITRD
>>> >>>> >-static void __init setup_initrd(void)
>>> >>>> >-{
>>> >>>> >-    extern char __initramfs_start[];
>>> >>>> >-    extern unsigned long __initramfs_size;
>>> >>>> >-    unsigned long size;
>>> >>>> >-
>>> >>>> >-    if (__initramfs_size > 0) {
>>> >>>> >-        initrd_start = (unsigned long)(&__initramfs_start);
>>> >>>> >-        initrd_end = initrd_start + __initramfs_size;
>>> >>>> >-    }
>>> >>>
>>> >>> The underlying problem is probably that __initramfs_size == 512 even
>>> >>> if there is no embedded initrd. Result is that initrd_start and initrd_end
>>> >>> are always overwritten, even if provided and even if there is no embedded
>>> >>> initrd. Result is that initrd_start and initrd_end are always overwritten,
>>> >>> and -initrd from the qemu command line is always ignored.
>>> >>>
>>> >>> A less invasive fix than mine would be
>>> >>>
>>> >>> -    if (__initramfs_size > 0) {
>>> >>> +    if (__initramfs_size > 0 && !initrd_start) {
>>> >>>
>>> >>> Any chance you can test that with your setup ?
>>> >>
>>> >>You should just delete the last four lines above.  They serve no purpose.
>>> >>
>>> >
>>> >You mean the entire if() statement plus the variable declarations ?
>>> >
>>> >That works for me, for both embedded initrd and initrd specified with
>>> >-initrd option, but we still need someone to test if it works for
>>> >Palmer's use case, ie with vmlinux (and possibly initrd) embedded in
>>> >bbl.
>>>
>>> This still boots my Fedora images
>>>
>>>    diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>>>    index db20dc630e7e..aee603123030 100644
>>>    --- a/arch/riscv/kernel/setup.c
>>>    +++ b/arch/riscv/kernel/setup.c
>>>    @@ -85,15 +85,8 @@ atomic_t hart_lottery;
>>>     #ifdef CONFIG_BLK_DEV_INITRD
>>>     static void __init setup_initrd(void)
>>>     {
>>>    -    extern char __initramfs_start[];
>>>    -    extern unsigned long __initramfs_size;
>>>         unsigned long size;
>>>    -    if (__initramfs_size > 0) {
>>>    -        initrd_start = (unsigned long)(&__initramfs_start);
>>>    -        initrd_end = initrd_start + __initramfs_size;
>>>    -    }
>>>    -
>>>         if (initrd_start >= initrd_end) {
>>>             printk(KERN_INFO "initrd not found or empty");
>>>             goto disable;
>>>
>>> but I have not tried an integrated initramfs.
>>
>> I tested the above both with external initrd and with integrated
>> initramfs; both work for me.
>>
>> Should I resend my patch, using the above, or do you want to create
>> a patch yourself ?
> 
> You should send one, then it'll go through my regular pre-PR testing flow to make sure it works on my end.  I just never trust these inline patches to be exact, even if it's unlikely there's any confusion on a patch this simple (at least, mechanically simple -- I'm afraid I still don't understand why the logic is incorrect).
> 

Done.

There is no need to override initrd_start and initrd_end; populate_rootfs()
uses __initramfs_start and __initramfs_size directly when loading a built-in
initramfs. initrd_start and initrd_end, on the other side, are for an external
initrd, loaded separately (and initialized in __early_init_dt_declare_initrd()).

Hope this helps,
Guenter