linux-kernel - Re: [RFC v2 07/12] powerpc: Macro the mask used for checking DSI exception

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Message-Id: <87r2ydajk9.fsf@skywalker.in.ibm.com>
Date:   Wed, 21 Jun 2017 12:55:42 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     Ram Pai <linuxram@...ibm.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, bsingharora@...il.com,
        dave.hansen@...el.com, hbabu@...ibm.com, linuxram@...ibm.com
Subject: Re: [RFC v2 07/12] powerpc: Macro the mask used for checking DSI exception

Ram Pai <linuxram@...ibm.com> writes:

> Replace the magic number used to check for DSI exception
> with a meaningful value.
>
> Signed-off-by: Ram Pai <linuxram@...ibm.com>
> ---
>  arch/powerpc/include/asm/reg.h       | 9 ++++++++-
>  arch/powerpc/kernel/exceptions-64s.S | 2 +-
>  2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
> index 7e50e47..2dcb8a1 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -272,16 +272,23 @@
>  #define SPRN_DAR	0x013	/* Data Address Register */
>  #define SPRN_DBCR	0x136	/* e300 Data Breakpoint Control Reg */
>  #define SPRN_DSISR	0x012	/* Data Storage Interrupt Status Register */
> +#define   DSISR_BIT32		0x80000000	/* not defined */
>  #define   DSISR_NOHPTE		0x40000000	/* no translation found */
> +#define   DSISR_PAGEATTR_CONFLT	0x20000000	/* page attribute conflict */
> +#define   DSISR_BIT35		0x10000000	/* not defined */
>  #define   DSISR_PROTFAULT	0x08000000	/* protection fault */
>  #define   DSISR_BADACCESS	0x04000000	/* bad access to CI or G */
>  #define   DSISR_ISSTORE		0x02000000	/* access was a store */
>  #define   DSISR_DABRMATCH	0x00400000	/* hit data breakpoint */
> -#define   DSISR_NOSEGMENT	0x00200000	/* SLB miss */
>  #define   DSISR_KEYFAULT	0x00200000	/* Key fault */
> +#define   DSISR_BIT43		0x00100000	/* not defined */
>  #define   DSISR_UNSUPP_MMU	0x00080000	/* Unsupported MMU config */
>  #define   DSISR_SET_RC		0x00040000	/* Failed setting of R/C bits */
>  #define   DSISR_PGDIRFAULT      0x00020000      /* Fault on page directory */
> +#define   DSISR_PAGE_FAULT_MASK (DSISR_BIT32 | \
> +				DSISR_PAGEATTR_CONFLT | \
> +				DSISR_BADACCESS |       \
> +				DSISR_BIT43)
>  #define SPRN_TBRL	0x10C	/* Time Base Read Lower Register (user, R/O) */
>  #define SPRN_TBRU	0x10D	/* Time Base Read Upper Register (user, R/O) */
>  #define SPRN_CIR	0x11B	/* Chip Information Register (hyper, R/0) */
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index ae418b8..3fd0528 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -1411,7 +1411,7 @@ USE_TEXT_SECTION()
>  	.balign	IFETCH_ALIGN_BYTES
>  do_hash_page:
>  #ifdef CONFIG_PPC_STD_MMU_64
> -	andis.	r0,r4,0xa410		/* weird error? */
> +	andis.	r0,r4,DSISR_PAGE_FAULT_MASK@h
>  	bne-	handle_page_fault	/* if not, try to insert a HPTE */
>  	andis.  r0,r4,DSISR_DABRMATCH@h
>  	bne-    handle_dabr_fault


Thanks for doing this. I always wondered what that 0xa410 indicates. Now
tha it is documented, I am wondering are those the only DSISR values
that we want to check early ? You also added few bit positions that is
expected to carry value 0 ? But then excluded BIT35. Any reason ?

-aneesh