linux-kernel - Re: linux-next: build failure after merge of the bitmap tree

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Message-ID: <YynS8Z7BLy0/Vu1j@yury-laptop>
Date:   Tue, 20 Sep 2022 07:49:21 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the bitmap tree

On Tue, Sep 20, 2022 at 06:08:39PM +1000, Stephen Rothwell wrote:
> Hi all,
> 
> After merging the bitmap tree, today's linux-next build (powerpc
> allyesconfig) failed like this:
> 
> ld: arch/powerpc/kernel/head_64.o: in function `generic_secondary_common_init':
> (.text+0x545e): undefined reference to `nr_cpu_ids'
> 
> Caused by commit
> 
>   c90c5bd9f2d6 ("lib/cpumask: add FORCE_NR_CPUS config option")
> 
> This build has CONFIG_FORCE_NR_CPUS set but the (assembler) code expects
> nr_cpu_ids to be a variable ...
> 
> I have reverted that commit for today.

Thanks for report, Stephen.

I did PPC build for bitmap-for-next, and it was OK on top of
v6-rc4. On today's -next I can reproduce the failure. It's weird
because the code in trouble was added at 2011 in 768d18ad6d5e6
("powerpc: Don't search for paca in freed memory").

Anyways, the fix is straightforward. I updated the bitmap-for-next
with it, and will send it for review shortly.
--

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index cf2c08902c05..7cb97881635e 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -400,7 +400,11 @@ generic_secondary_common_init:
 #else
        LOAD_REG_ADDR(r8, paca_ptrs)    /* Load paca_ptrs pointe         */
        ld      r8,0(r8)                /* Get base vaddr of array       */
+#if (NR_CPUS == 1) || defined(CONFIG_FORCE_NR_CPUS)
+       LOAD_REG_IMMEDIATE(r7, NR_CPUS)
+#else
        LOAD_REG_ADDR(r7, nr_cpu_ids)   /* Load nr_cpu_ids address       */
+#endif
        lwz     r7,0(r7)                /* also the max paca allocated   */
        li      r5,0                    /* logical cpu id                */
 1: