linux-kernel - Re: [PATCH] arch/{mips,sparc,microblaze,powerpc}: Don't enable pagefault/preempt twice

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Date:   Thu, 21 May 2020 18:11:08 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     ira.weiny@...el.com, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, dri-devel@...ts.freedesktop.org,
        Christian Koenig <christian.koenig@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] arch/{mips,sparc,microblaze,powerpc}: Don't enable
 pagefault/preempt twice

On 5/21/20 5:46 PM, Al Viro wrote:
> On Thu, May 21, 2020 at 11:46:12PM +0100, Al Viro wrote:
>> On Thu, May 21, 2020 at 03:20:46PM -0700, Guenter Roeck wrote:
>>> On 5/21/20 10:27 AM, Al Viro wrote:
>>>> On Tue, May 19, 2020 at 09:54:22AM -0700, Guenter Roeck wrote:
>>>>> On Mon, May 18, 2020 at 11:48:43AM -0700, ira.weiny@...el.com wrote:
>>>>>> From: Ira Weiny <ira.weiny@...el.com>
>>>>>>
>>>>>> The kunmap_atomic clean up failed to remove one set of pagefault/preempt
>>>>>> enables when vaddr is not in the fixmap.
>>>>>>
>>>>>> Fixes: bee2128a09e6 ("arch/kunmap_atomic: consolidate duplicate code")
>>>>>> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
>>>>>
>>>>> microblazeel works with this patch, as do the nosmp sparc32 boot tests,
>>>>> but sparc32 boot tests with SMP enabled still fail with lots of messages
>>>>> such as:
>>>>
>>>> BTW, what's your setup for sparc32 boot tests?  IOW, how do you manage to
>>>> shrink the damn thing enough to have the loader cope with it?  I hadn't
>>>> been able to do that for the current mainline ;-/
>>>>
>>>
>>> defconfig seems to work just fine, even after enabling various debug
>>> and file system options.
>>
>> The hell?  How do you manage to get the kernel in?  sparc32_defconfig
>> ends up with 5316876 bytes unpacked...
> 
> Incidentally, trying to load it via -kernel/-initrd leads to
> Configuration device id QEMU version 1 machine id 64
> Probing SBus slot 0 offset 0
> Probing SBus slot 1 offset 0
> Probing SBus slot 2 offset 0
> Probing SBus slot 3 offset 0
> Probing SBus slot 15 offset 0
> Invalid FCode start byte
> CPUs: 1 x TI,TMS390Z55
> UUID: 00000000-0000-0000-0000-000000000000
> Welcome to OpenBIOS v1.1 built on Dec 27 2018 19:17
>   Type 'help' for detailed information
> [sparc] Kernel already loaded
> switching to new context:
> PROMLIB: obio_ranges 1
> PROMLIB: Sun Boot Prom Version 3 Revision 2
> Linux version 5.7.0-rc1-00002-gcf51e129b968 (al@...e) (gcc version 6.3.0 20170516 (Debian 6.3.0-18), GNU ld (GNU Binutils for Debian) 2.28) #32 Thu May 21 18:36:07 EDT 2020
> printk: bootconsole [earlyprom0] enabled
> ARCH: SUN4M
> TYPE: Sun4m SparcStation10/20
> Ethernet address: 52:54:00:12:34:56
> 303MB HIGHMEM available.
> OF stdout device is: /obio/zs@0,100000:a
> PROM: Built device tree with 30051 bytes of memory.
> Booting Linux...
> Power off control detected.
> Kernel panic - not syncing: Failed to allocate memory for percpu areas.
> CPU: 0 PID: 0 Comm: swapper Not tainted 5.7.0-rc1-00002-gcf51e129b968 #32
> [f04f92a8 : 
> setup_per_cpu_areas+0x58/0x90 ] 
> [f04edbf4 : 
> start_kernel+0xc0/0x4a0 ] 
> [f04ed43c : 
> continue_boot+0x324/0x334 ] 
> [00000000 : 
> 0x0 ] 
> 
> Press Stop-A (L1-A) from sun keyboard or send break
> twice on console to return to the boot prom
> ---[ end Kernel panic - not syncing: Failed to allocate memory for percpu areas. ]---
> 
> Giving guest more RAM doesn't change the outcome (well, the number HIGHMEM line is
> obviously higher, but that's it).
> 
> So which sparc32 kernel have you booted with defconfig and how have you done
> that?
> 

Mainline, with:

qemu-system-sparc -M SS-4 -kernel arch/sparc/boot/zImage -no-reboot \
	-snapshot -drive file=rootfs.ext2,format=raw,if=scsi \
	-append "panic=-1 slub_debug=FZPUA root=/dev/sda console=ttyS0"
	-nographic -monitor none

The machine doesn't really matter, though. The root file system is built
with buildroot.

Note that I carry two reverts in my qemu images.

Revert "tcx: switch to load_image_mr() and remove prom_addr hack"
Revert "cg3: switch to load_image_mr() and remove prom-addr hack"

I have been carrying those since ~2017. I didn't check recently
if they are still needed.

If sparc32 is no longer supported in the upstream kernel,
would it possibly make sense remove its support ?

Guenter