2021-11-27 02:07:17

by Vladimir Oltean

[permalink] [raw]
Subject: [PATCH] powerpc/mm: fix early initialization failure for MMUs with no hash table

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: [email protected]
Signed-off-by: Vladimir Oltean <[email protected]>
---
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



2021-11-27 15:51:01

by Vladimir Oltean

[permalink] [raw]
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: [email protected]
> Signed-off-by: Vladimir Oltean <[email protected]>
> ---
> 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.

2021-11-27 19:54:10

by Christophe Leroy

[permalink] [raw]
Subject: Re: [PATCH] powerpc/mm: fix early initialization failure for MMUs with no hash table



Le 27/11/2021 à 03:04, Vladimir Oltean a écrit :
> 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: [email protected]
> Signed-off-by: Vladimir Oltean <[email protected]>

Thanks for you patch.

However, it should already be fixed in 5.16-rc2 with the following
commit :
https://github.com/torvalds/linux/commit/5b54860943dc4681be5de2fc287408c7ce274dfc

Christophe

> ---
> 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
>