linux-kernel - Re: [PATCH] powerpc/mm: fix early initialization failure for MMUs with no hash table

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Message-ID: <20211127154854.lnu3blrsjm6wfkni@skbuf>
Date:   Sat, 27 Nov 2021 15:48:55 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
CC:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] powerpc/mm: fix early initialization failure for MMUs
 with no hash table

On Sat, Nov 27, 2021 at 04:04:48AM +0200, Vladimir Oltean wrote:
> The blamed patch attempted to do a trivial conversion of
> map_mem_in_cams() by adding an extra "bool init" argument, but by
> mistake, changed the way in which two call sites pass the other boolean
> argument, "bool dry_run".
> 
> As a result, early_init_this_mmu() now calls map_mem_in_cams() with
> dry_run=true, and setup_initial_memory_limit() calls with dry_run=false,
> both of which are unintended changes.
> 
> This makes the kernel boot process hang here:
> 
> [    0.045211] e500 family performance monitor hardware support registered
> [    0.051891] rcu: Hierarchical SRCU implementation.
> [    0.057791] smp: Bringing up secondary CPUs ...
> 
> Issue noticed on a Freescale T1040.
> 
> Fixes: 52bda69ae8b5 ("powerpc/fsl_booke: Tell map_mem_in_cams() if init is done")
> Cc: stable@...r.kernel.org
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---
>  arch/powerpc/mm/nohash/tlb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/mm/nohash/tlb.c b/arch/powerpc/mm/nohash/tlb.c
> index 89353d4f5604..647bf454a0fa 100644
> --- a/arch/powerpc/mm/nohash/tlb.c
> +++ b/arch/powerpc/mm/nohash/tlb.c
> @@ -645,7 +645,7 @@ static void early_init_this_mmu(void)
>  
>  		if (map)
>  			linear_map_top = map_mem_in_cams(linear_map_top,
> -							 num_cams, true, true);
> +							 num_cams, false, true);
>  	}
>  #endif
>  
> @@ -766,7 +766,7 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
>  		num_cams = (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) / 4;
>  
>  		linear_sz = map_mem_in_cams(first_memblock_size, num_cams,
> -					    false, true);
> +					    true, true);
>  
>  		ppc64_rma_size = min_t(u64, linear_sz, 0x40000000);
>  	} else
> -- 
> 2.25.1
>

This is a duplicate of commit 5b54860943dc ("powerpc/book3e: Fix TLBCAM preset at boot"),
looks like I'm late to the party. That commit unbricks my board, so
please drop this patch.