Subject: Re: [PATCH] powerpc/mm: Fix hash computation function

From: Mike Qiu <[email-masked]>
Date: Wed, 30 Jan 2013 15:23:53 +0800

With the fix, the machine can boot up successfully

Tested-by: Mike Qiu <[email-masked]>

于 2013/1/30 13:40, Aneesh Kumar K.V 写道:
> From: "Aneesh Kumar K.V" <[email-masked]>
>
> The ASM version of hash computation function was truncating the upper bit.
> Make the ASM version similar to hpt_hash function. Remove masking vsid bits.
> Without this patch, we observed hang during bootup due to not satisfying page
> fault request correctly. The fault handler used wrong hash values to update
> the HPTE. Hence we kept looping with page fault.
>
> hash_page(ea=000001003e260008, access=203, trap=300 ip=3fff91787134 dsisr 42000000
> The computed value of hash 000000000f22f390
> update: avpnv=4003e46054003e00, hash=000000000722f390, f=80000006, psize: 2 ...
>
> Reported-by: Mike Qiu <[email-masked]>
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> ---
>  arch/powerpc/mm/hash_low_64.S |   62 +++++++++++++++++++++++------------------
>  1 file changed, 35 insertions(+), 27 deletions(-)
>
> diff --git a/arch/powerpc/mm/hash_low_64.S b/arch/powerpc/mm/hash_low_64.S
> index 5658508..7443481 100644
> --- a/arch/powerpc/mm/hash_low_64.S
> +++ b/arch/powerpc/mm/hash_low_64.S
> @@ -115,11 +115,13 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
>  	sldi	r29,r5,SID_SHIFT - VPN_SHIFT
>  	rldicl  r28,r3,64 - VPN_SHIFT,64 - (SID_SHIFT - VPN_SHIFT)
>  	or	r29,r28,r29
> -
> -	/* Calculate hash value for primary slot and store it in r28 */
> -	rldicl	r5,r5,0,25		/* vsid & 0x0000007fffffffff */
> -	rldicl	r0,r3,64-12,48		/* (ea >> 12) & 0xffff */
> -	xor	r28,r5,r0
> +	/*
> +	 * Calculate hash value for primary slot and store it in r28
> +	 * r3 = va, r5 = vsid
> +	 * r0 = (va >> 12) & ((1ul << (28 - 12)) -1)
> +	 */
> +	rldicl	r0,r3,64-12,48
> +	xor	r28,r5,r0		/* hash */
>  	b	4f
>
>  3:	/* Calc vpn and put it in r29 */
> @@ -130,11 +132,12 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
>  	/*
>  	 * calculate hash value for primary slot and
>  	 * store it in r28 for 1T segment
> +	 * r3 = va, r5 = vsid
>  	 */
> -	rldic	r28,r5,25,25		/* (vsid << 25) & 0x7fffffffff */
> -	clrldi	r5,r5,40		/* vsid & 0xffffff */
> -	rldicl	r0,r3,64-12,36		/* (ea >> 12) & 0xfffffff */
> -	xor	r28,r28,r5
> +	sldi	r28,r5,25		/* vsid << 25 */
> +	/* r0 =  (va >> 12) & ((1ul << (40 - 12)) -1) */
> +	rldicl	r0,r3,64-12,36
> +	xor	r28,r28,r5		/* vsid ^ ( vsid << 25) */
>  	xor	r28,r28,r0		/* hash */
>
>  	/* Convert linux PTE bits into HW equivalents */
> @@ -407,11 +410,13 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
>  	 */
>  	rldicl  r28,r3,64 - VPN_SHIFT,64 - (SID_SHIFT - VPN_SHIFT)
>  	or	r29,r28,r29
> -
> -	/* Calculate hash value for primary slot and store it in r28 */
> -	rldicl	r5,r5,0,25		/* vsid & 0x0000007fffffffff */
> -	rldicl	r0,r3,64-12,48		/* (ea >> 12) & 0xffff */
> -	xor	r28,r5,r0
> +	/*
> +	 * Calculate hash value for primary slot and store it in r28
> +	 * r3 = va, r5 = vsid
> +	 * r0 = (va >> 12) & ((1ul << (28 - 12)) -1)
> +	 */
> +	rldicl	r0,r3,64-12,48
> +	xor	r28,r5,r0		/* hash */
>  	b	4f
>
>  3:	/* Calc vpn and put it in r29 */
> @@ -426,11 +431,12 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
>  	/*
>  	 * Calculate hash value for primary slot and
>  	 * store it in r28  for 1T segment
> +	 * r3 = va, r5 = vsid
>  	 */
> -	rldic	r28,r5,25,25		/* (vsid << 25) & 0x7fffffffff */
> -	clrldi	r5,r5,40		/* vsid & 0xffffff */
> -	rldicl	r0,r3,64-12,36		/* (ea >> 12) & 0xfffffff */
> -	xor	r28,r28,r5
> +	sldi	r28,r5,25		/* vsid << 25 */
> +	/* r0 = (va >> 12) & ((1ul << (40 - 12)) -1) */
> +	rldicl	r0,r3,64-12,36
> +	xor	r28,r28,r5		/* vsid ^ ( vsid << 25) */
>  	xor	r28,r28,r0		/* hash */
>
>  	/* Convert linux PTE bits into HW equivalents */
> @@ -752,25 +758,27 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
>  	rldicl  r28,r3,64 - VPN_SHIFT,64 - (SID_SHIFT - VPN_SHIFT)
>  	or	r29,r28,r29
>
> -	/* Calculate hash value for primary slot and store it in r28 */
> -	rldicl	r5,r5,0,25		/* vsid & 0x0000007fffffffff */
> -	rldicl	r0,r3,64-16,52		/* (ea >> 16) & 0xfff */
> -	xor	r28,r5,r0
> +	/* Calculate hash value for primary slot and store it in r28
> +	 * r3 = va, r5 = vsid
> +	 * r0 = (va >> 16) & ((1ul << (28 - 16)) -1)
> +	 */
> +	rldicl	r0,r3,64-16,52
> +	xor	r28,r5,r0		/* hash */
>  	b	4f
>
>  3:	/* Calc vpn and put it in r29 */
>  	sldi	r29,r5,SID_SHIFT_1T - VPN_SHIFT
>  	rldicl  r28,r3,64 - VPN_SHIFT,64 - (SID_SHIFT_1T - VPN_SHIFT)
>  	or	r29,r28,r29
> -
>  	/*
>  	 * calculate hash value for primary slot and
>  	 * store it in r28 for 1T segment
> +	 * r3 = va, r5 = vsid
>  	 */
> -	rldic	r28,r5,25,25		/* (vsid << 25) & 0x7fffffffff */
> -	clrldi	r5,r5,40		/* vsid & 0xffffff */
> -	rldicl	r0,r3,64-16,40		/* (ea >> 16) & 0xffffff */
> -	xor	r28,r28,r5
> +	sldi	r28,r5,25		/* vsid << 25 */
> +	/* r0 = (va >> 16) & ((1ul << (40 - 16)) -1) */
> +	rldicl	r0,r3,64-16,40
> +	xor	r28,r28,r5		/* vsid ^ ( vsid << 25) */
>  	xor	r28,r28,r0		/* hash */
>
>  	/* Convert linux PTE bits into HW equivalents */