linux-kernel - Re: [PATCH] powerpc: add support for folded p4d page tables

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Message-ID: <87tv5728sw.fsf@mpe.ellerman.id.au>
Date:   Tue, 07 Jan 2020 15:24:15 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH] powerpc: add support for folded p4d page tables

Mike Rapoport <rppt@...nel.org> writes:
> On Mon, Jan 06, 2020 at 02:31:41PM +1100, Michael Ellerman wrote:
>> Mike Rapoport <rppt@...nel.org> writes:
>> > Any updates on this?
>> 
>> It's very ... big, and kind of intrusive.
>
> I've tried to split it to several smaller ones, but I couldn't find a way
> to do it without breaking bisectability.

Yeah I didn't necessarily mean splitting it, it's just a lot of churn.

It seems to break qemu mac99 booting pmac32 defconfig, haven't had time
to look any further:

  Loading compiled-in X.509 certificates
  rtc-generic rtc-generic: setting system clock to 2020-01-07T02:42:59 UTC (1578364979)
  BUG: Unable to handle kernel unaligned access at 0xf10af004
  Faulting instruction address: 0xc01cc6c4
  Vector: 600 (Alignment) at [ef0b5de0]
      pc: c01cc6c4: f_dupfd+0x6c/0xb8
      lr: c01cc698: f_dupfd+0x40/0xb8
      sp: ef0b5e98
     msr: 9032
     dar: f10af004
   dsisr: 40000140
    current = 0xef0b0000
      pid   = 1, comm = swapper
  Linux version 5.5.0-rc2+ (michael@...ine1-p1) (gcc version 9.2.1 20191127 (Ubuntu 9.2.1-20ubuntu3)) #8 Tue Jan 7 13:38:04 AEDT 2020
  enter ? for help
  [ef0b5eb8] c000550c console_on_rootfs+0x44/0x90
  [ef0b5ed8] c090d7c0 kernel_init_freeable+0x1a4/0x24c
  [ef0b5f18] c0005770 kernel_init+0x18/0x108
  [ef0b5f38] c0017274 ret_from_kernel_thread+0x14/0x1c
  FAIL! Booting BE pmac32


cheers