linux-kernel - Re: [PATCH] mm/vmalloc: track which page-table levels were modified

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Message-ID: <d7dbd2e2-5547-01e5-296d-23d4e982b2cc@roeck-us.net>
Date:   Tue, 9 Jun 2020 10:07:43 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/vmalloc: track which page-table levels were modified

On 6/9/20 9:23 AM, Joerg Roedel wrote:
> Hi Guenter,
> 
> On Tue, Jun 09, 2020 at 07:15:42AM -0700, Guenter Roeck wrote:
>> To build csky images, you have to disable CONFIG_FRAME_POINTER or use a
>> non-upstream compiler. To build any images reliably, you have to disable
>> CONFIG_GCC_PLUGIN_RANDSTRUCT or use a version of gcc old enough to not
>> support it (gcc 6.x is fine). For mips, you have to specify ARCH and
>> CROSS_COMPILE as environment variables.
> 
> My test setup builds defconfigs for all architectures using the gcc-9.3
> based cross-compilers from kernel.org (except the ones I have no
> compiler for). That used to work for CSky and MIPS(64) when working on
> my vmalloc changes.
> 
> On MIPS the build failure looks like some Makefile breakage, but I
> didn't dive deeper into that.
> 

Yes, that was discussed elsewhere. A fix has been submitted and should
hopefully find its way into the kernel sometime soon.

> For CSky the compiler complains about not supporting '-mbacktrace'.
> 

Yes, that is why you have to disable CONFIG_FRAME_POINTER.
'-mbacktrace' is not supported in upstream versions of gcc for csky;
it is only supported in the out-of-tree csky toolchain.

>> alpha is a lost case. The offending commit is 0f1c9688a19 ("tty/sysrq:
>> alpha: export and use __sysrq_get_key_op()"); it looks like that wasn't
>> build tested. It can not be reverted easily because of subsequent changes.
> 
> The below diff fixed the alpha build for me, but I am sure another fix
> is already queued somewhere.
> 

Let's hope it is.

Thanks,
Guenter

> diff --git a/arch/alpha/kernel/setup.c b/arch/alpha/kernel/setup.c
> index 6fa802c495b4..8f4ad63a3a9a 100644
> --- a/arch/alpha/kernel/setup.c
> +++ b/arch/alpha/kernel/setup.c
> @@ -431,8 +431,13 @@ register_cpus(void)
>  arch_initcall(register_cpus);
>  
>  #ifdef CONFIG_MAGIC_SYSRQ
> +static void sysrq_reboot_handler(int unused)
> +{
> +	machine_halt();
> +}
> +
>  static const struct sysrq_key_op srm_sysrq_reboot_op = {
> -	.handler	= machine_halt,
> +	.handler	= sysrq_reboot_handler,
>  	.help_msg       = "reboot(b)",
>  	.action_msg     = "Resetting",
>  	.enable_mask    = SYSRQ_ENABLE_BOOT,
>