linux-kernel - Re: [PATCH RESEND] mips: switch to NO

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Date:   Thu, 6 Sep 2018 08:30:11 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     "Fancer's opinion" <fancer.lancer@...il.com>
Cc:     Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Huacai Chen <chenhc@...ote.com>,
        Michal Hocko <mhocko@...nel.org>,
        Linux-MIPS <linux-mips@...ux-mips.org>, linux-mm@...ck.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] mips: switch to NO_BOOTMEM

Hi Sergey,

On Wed, Sep 05, 2018 at 11:09:13PM +0300, Fancer's opinion wrote:
> Hello, Mike
> Could you CC me next time you send that larger patchset?

The larger patchset is here:

https://lore.kernel.org/lkml/1536163184-26356-1-git-send-email-rppt@linux.vnet.ibm.com/
 
> -Sergey
> 
> 
> On Wed, Sep 5, 2018 at 9:38 PM Mike Rapoport <rppt@...ux.vnet.ibm.com> wrote:
> 
>     On Wed, Sep 05, 2018 at 10:47:10AM -0700, Paul Burton wrote:
>     > Hi Mike,
>     >
>     > On Sat, Sep 01, 2018 at 12:17:48AM +0300, Mike Rapoport wrote:
>     > > On Thu, Aug 30, 2018 at 02:48:57PM -0700, Paul Burton wrote:
>     > > > On Mon, Aug 27, 2018 at 10:59:35AM +0300, Mike Rapoport wrote:
>     > > > > MIPS already has memblock support and all the memory is already
>     registered
>     > > > > with it.
>     > > > >
>     > > > > This patch replaces bootmem memory reservations with memblock ones
>     and
>     > > > > removes the bootmem initialization.
>     > > > >
>     > > > > Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
>     > > > > ---
>     > > > >
>     > > > >  arch/mips/Kconfig                      |  1 +
>     > > > >  arch/mips/kernel/setup.c               | 89
>     +++++-----------------------------
>     > > > >  arch/mips/loongson64/loongson-3/numa.c | 34 ++++++-------
>     > > > >  arch/mips/sgi-ip27/ip27-memory.c       | 11 ++---
>     > > > >  4 files changed, 33 insertions(+), 102 deletions(-)
>     > > >
>     > > > Thanks for working on this. Unfortunately it breaks boot for at least
>     a
>     > > > 32r6el_defconfig kernel on QEMU:
>     > > >
>     > > >   $ qemu-system-mips64el \
>     > > >     -M boston \
>     > > >     -kernel arch/mips/boot/vmlinux.gz.itb \
>     > > >     -serial stdio \
>     > > >     -append "earlycon=uart8250,mmio32,0x17ffe000,115200 console=
>     ttyS0,115200 debug memblock=debug mminit_loglevel=4"
>     > > >   [    0.000000] Linux version 4.19.0-rc1-00008-g82d0f342eecd
>     (pburton@...rton-laptop) (gcc version 8.1.0 (GCC)) #23 SMP Thu Aug 30
>     14:38:06 PDT 2018
>     > > >   [    0.000000] CPU0 revision is: 0001a900 (MIPS I6400)
>     > > >   [    0.000000] FPU revision is: 20f30300
>     > > >   [    0.000000] MSA revision is: 00000300
>     > > >   [    0.000000] MIPS: machine is img,boston
>     > > >   [    0.000000] Determined physical RAM map:
>     > > >   [    0.000000]  memory: 10000000 @ 00000000 (usable)
>     > > >   [    0.000000]  memory: 30000000 @ 90000000 (usable)
>     > > >   [    0.000000] earlycon: uart8250 at MMIO32 0x17ffe000 (options
>     '115200')
>     > > >   [    0.000000] bootconsole [uart8250] enabled
>     > > >   [    0.000000] memblock_reserve: [0x00000000-0x009a8fff]
>     setup_arch+0x224/0x718
>     > > >   [    0.000000] memblock_reserve: [0x01360000-0x01361ca7]
>     setup_arch+0x3d8/0x718
>     > > >   [    0.000000] Initrd not found or empty - disabling initrd
>     > > >   [    0.000000] memblock_virt_alloc_try_nid: 7336 bytes align=0x40
>     nid=-1 from=0x00000000 max_addr=0x00000000
>     early_init_dt_alloc_memory_arch+0x20/0x2c
>     > > >   [    0.000000] memblock_reserve: [0xbfffe340-0xbfffffe7]
>     memblock_virt_alloc_internal+0x120/0x1ec
>     > > >   <hang>
>     > > >
>     > > > It looks like we took a TLB store exception after calling memset()
>     with
>     > > > a bogus address from memblock_virt_alloc_try_nid() or something
>     inlined
>     > > > into it.
>     > >
>     > > Memblock tries to allocate from the top and the resulting address ends
>     up
>     > > in the high memory.
>     > >
>     > > With the hunk below I was able to get to "VFS: Cannot open root device"
>     > >
>     > > diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
>     > > index 4114d3c..4a9b0f7 100644
>     > > --- a/arch/mips/kernel/setup.c
>     > > +++ b/arch/mips/kernel/setup.c
>     > > @@ -577,6 +577,8 @@ static void __init bootmem_init(void)
>     > >          * Reserve initrd memory if needed.
>     > >          */
>     > >         finalize_initrd();
>     > > +
>     > > +       memblock_set_bottom_up(true);
>     > >  }
>     >
>     > That does seem to fix it, and some basic tests are looking good.
> 
>     The bottom up mode has the downside of allocating memory below
>     MAX_DMA_ADDRESS.
> 
>     I'd like to check if memblock_set_current_limit(max_low_pfn) will also fix
>     the issue, at least with the limited tests I can do with qemu.
> 
>     > I notice you submitted this as part of your larger series to remove
>     > bootmem - are you still happy for me to take this one through mips-next?
> 
>     Sure, I've just posted it as the part of the larger series for
>     completeness.
> 
>     I believe that in the next few days I'll be able to verify whether
>     memblock_set_current_limit() can be used instead of
>     memblock_set_bottom_up() and I'll resend the patch then.
> 
>     > Thanks,
>     >     Paul
>     >
> 
>     --
>     Sincerely yours,
>     Mike.
> 
> 

-- 
Sincerely yours,
Mike.