[PATCH] powerpc/rtas: fix early boot failure.

[PATCH] powerpc/rtas: fix early boot failure.

[Christophe Leroy]

Commit 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing
stack pointer while in RTAS") changes the code to use a field in
thread struct to store the stack pointer while in RTAS instead of
using SPRN_SPRG2. It therefore converts all places which were
manipulating SPRN_SPRG2 to use that field. During early startup,
the zeroing of SPRN_SPRG2 has been replaced by a zeroing of that
field in thread struct. But at least in start_here, that's done
wrongly because it used the physical address of the fields while
MMU is on at that time.

So the virtual address of the field should be used instead, but in
the meantime, thread struct has already been zeroised and initialised
so we can just drop this initialisation.

Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Fixes: 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/head_32.S | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 48051c8977c5..e25b615e9f9e 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -851,10 +851,6 @@ __secondary_start:
 	tophys(r4,r2)
 	addi	r4,r4,THREAD	/* phys address of our thread_struct */
 	mtspr	SPRN_SPRG_THREAD,r4
-#ifdef CONFIG_PPC_RTAS
-	li	r3,0
-	stw	r3, RTAS_SP(r4)		/* 0 => not in RTAS */
-#endif
 	lis	r4, (swapper_pg_dir - PAGE_OFFSET)@h
 	ori	r4, r4, (swapper_pg_dir - PAGE_OFFSET)@l
 	mtspr	SPRN_SPRG_PGDIR, r4
@@ -941,10 +937,6 @@ start_here:
 	tophys(r4,r2)
 	addi	r4,r4,THREAD	/* init task's THREAD */
 	mtspr	SPRN_SPRG_THREAD,r4
-#ifdef CONFIG_PPC_RTAS
-	li	r3,0
-	stw	r3, RTAS_SP(r4)		/* 0 => not in RTAS */
-#endif
 	lis	r4, (swapper_pg_dir - PAGE_OFFSET)@h
 	ori	r4, r4, (swapper_pg_dir - PAGE_OFFSET)@l
 	mtspr	SPRN_SPRG_PGDIR, r4
-- 
2.13.3

Re: [PATCH] powerpc/rtas: fix early boot failure.

[Larry Finger]

On 3/25/19 3:43 AM, Christophe Leroy wrote:
> Commit 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing
> stack pointer while in RTAS") changes the code to use a field in
> thread struct to store the stack pointer while in RTAS instead of
> using SPRN_SPRG2. It therefore converts all places which were
> manipulating SPRN_SPRG2 to use that field. During early startup,
> the zeroing of SPRN_SPRG2 has been replaced by a zeroing of that
> field in thread struct. But at least in start_here, that's done
> wrongly because it used the physical address of the fields while
> MMU is on at that time.
> 
> So the virtual address of the field should be used instead, but in
> the meantime, thread struct has already been zeroised and initialised
> so we can just drop this initialisation.
> 
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Fixes: 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Tested-by: Larry Finger <Larry.Finger@lwfinger.net>

My PPC box now boots OK.

Larry

Re: [PATCH] powerpc/rtas: fix early boot failure.

[Christophe Leroy]

Michael,

Looks like you missed this fix for rc3.

Christophe

Le 25/03/2019 à 09:43, Christophe Leroy a écrit :
> Commit 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing
> stack pointer while in RTAS") changes the code to use a field in
> thread struct to store the stack pointer while in RTAS instead of
> using SPRN_SPRG2. It therefore converts all places which were
> manipulating SPRN_SPRG2 to use that field. During early startup,
> the zeroing of SPRN_SPRG2 has been replaced by a zeroing of that
> field in thread struct. But at least in start_here, that's done
> wrongly because it used the physical address of the fields while
> MMU is on at that time.
> 
> So the virtual address of the field should be used instead, but in
> the meantime, thread struct has already been zeroised and initialised
> so we can just drop this initialisation.
> 
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Fixes: 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>   arch/powerpc/kernel/head_32.S | 8 --------
>   1 file changed, 8 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
> index 48051c8977c5..e25b615e9f9e 100644
> --- a/arch/powerpc/kernel/head_32.S
> +++ b/arch/powerpc/kernel/head_32.S
> @@ -851,10 +851,6 @@ __secondary_start:
>   	tophys(r4,r2)
>   	addi	r4,r4,THREAD	/* phys address of our thread_struct */
>   	mtspr	SPRN_SPRG_THREAD,r4
> -#ifdef CONFIG_PPC_RTAS
> -	li	r3,0
> -	stw	r3, RTAS_SP(r4)		/* 0 => not in RTAS */
> -#endif
>   	lis	r4, (swapper_pg_dir - PAGE_OFFSET)@h
>   	ori	r4, r4, (swapper_pg_dir - PAGE_OFFSET)@l
>   	mtspr	SPRN_SPRG_PGDIR, r4
> @@ -941,10 +937,6 @@ start_here:
>   	tophys(r4,r2)
>   	addi	r4,r4,THREAD	/* init task's THREAD */
>   	mtspr	SPRN_SPRG_THREAD,r4
> -#ifdef CONFIG_PPC_RTAS
> -	li	r3,0
> -	stw	r3, RTAS_SP(r4)		/* 0 => not in RTAS */
> -#endif
>   	lis	r4, (swapper_pg_dir - PAGE_OFFSET)@h
>   	ori	r4, r4, (swapper_pg_dir - PAGE_OFFSET)@l
>   	mtspr	SPRN_SPRG_PGDIR, r4
> 

Re: powerpc/rtas: fix early boot failure.

[Michael Ellerman]

On Mon, 2019-03-25 at 08:43:33 UTC, Christophe Leroy wrote:
> Commit 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing
> stack pointer while in RTAS") changes the code to use a field in
> thread struct to store the stack pointer while in RTAS instead of
> using SPRN_SPRG2. It therefore converts all places which were
> manipulating SPRN_SPRG2 to use that field. During early startup,
> the zeroing of SPRN_SPRG2 has been replaced by a zeroing of that
> field in thread struct. But at least in start_here, that's done
> wrongly because it used the physical address of the fields while
> MMU is on at that time.
> 
> So the virtual address of the field should be used instead, but in
> the meantime, thread struct has already been zeroised and initialised
> so we can just drop this initialisation.
> 
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Fixes: 0df977eafc79 ("powerpc/6xx: Don't use SPRN_SPRG2 for storing stack pointer while in RTAS")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Tested-by: Larry Finger <Larry.Finger@lwfinger.net>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/fd427103e8dfcb4b438269afd710b63e

cheers