linux-kernel - Re: [PATCH] openrisc: tlb miss handler optimizations

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Message-ID: <20131206102828.GA1369@chokladfabriken.org>
Date:	Fri, 6 Dec 2013 12:28:29 +0200
From:	Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
To:	linux-kernel@...r.kernel.org, linux@...ts.openrisc.net
Cc:	jonas@...thpole.se
Subject: Re: [PATCH] openrisc: tlb miss handler optimizations

Hi Jonas,

I realised that this haven't been picked up nor commented on (and that I missed
CC you on it).
Could you take a look at it?

Stefan

On Thu, Aug 01, 2013 at 10:46:10AM +0300, Stefan Kristiansson wrote:
> By slightly reorganizing the code, the number of registers
> used in the tlb miss handlers can be reduced by two,
> thus removing the need to save them to memory.
> 
> Also, some dead and commented out code is removed.
> 
> No functional change.
> 
> Signed-off-by: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
> ---
>  arch/openrisc/kernel/head.S | 141 +++++++++++++++-----------------------------
>  1 file changed, 46 insertions(+), 95 deletions(-)
> 
> diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
> index 1d3c9c2..eecc8df 100644
> --- a/arch/openrisc/kernel/head.S
> +++ b/arch/openrisc/kernel/head.S
> @@ -976,8 +976,6 @@ ENTRY(dtlb_miss_handler)
>  	EXCEPTION_STORE_GPR2
>  	EXCEPTION_STORE_GPR3
>  	EXCEPTION_STORE_GPR4
> -	EXCEPTION_STORE_GPR5
> -	EXCEPTION_STORE_GPR6
>  	/*
>  	 * get EA of the miss
>  	 */
> @@ -985,91 +983,70 @@ ENTRY(dtlb_miss_handler)
>  	/*
>  	 * pmd = (pmd_t *)(current_pgd + pgd_index(daddr));
>  	 */
> -	GET_CURRENT_PGD(r3,r5)		// r3 is current_pgd, r5 is temp
> +	GET_CURRENT_PGD(r3,r4)		// r3 is current_pgd, r4 is temp
>  	l.srli	r4,r2,0x18		// >> PAGE_SHIFT + (PAGE_SHIFT - 2)
>  	l.slli	r4,r4,0x2		// to get address << 2
> -	l.add	r5,r4,r3		// r4 is pgd_index(daddr)
> +	l.add	r3,r4,r3		// r4 is pgd_index(daddr)
>  	/*
>  	 * if (pmd_none(*pmd))
>  	 *   goto pmd_none:
>  	 */
> -	tophys	(r4,r5)
> +	tophys	(r4,r3)
>  	l.lwz	r3,0x0(r4)		// get *pmd value
>  	l.sfne	r3,r0
>  	l.bnf	d_pmd_none
> -	 l.andi	r3,r3,~PAGE_MASK //0x1fff		// ~PAGE_MASK
> -	/*
> -	 * if (pmd_bad(*pmd))
> -	 *   pmd_clear(pmd)
> -	 *   goto pmd_bad:
> -	 */
> -//	l.sfeq	r3,r0			// check *pmd value
> -//	l.bf	d_pmd_good
> -	l.addi	r3,r0,0xffffe000	// PAGE_MASK
> -//	l.j	d_pmd_bad
> -//	l.sw	0x0(r4),r0		// clear pmd
> +	 l.addi	r3,r0,0xffffe000	// PAGE_MASK
> +
>  d_pmd_good:
>  	/*
>  	 * pte = *pte_offset(pmd, daddr);
>  	 */
>  	l.lwz	r4,0x0(r4)		// get **pmd value
>  	l.and	r4,r4,r3		// & PAGE_MASK
> -	l.srli	r5,r2,0xd		// >> PAGE_SHIFT, r2 == EEAR
> -	l.andi	r3,r5,0x7ff		// (1UL << PAGE_SHIFT - 2) - 1
> +	l.srli	r2,r2,0xd		// >> PAGE_SHIFT, r2 == EEAR
> +	l.andi	r3,r2,0x7ff		// (1UL << PAGE_SHIFT - 2) - 1
>  	l.slli	r3,r3,0x2		// to get address << 2
>  	l.add	r3,r3,r4
> -	l.lwz	r2,0x0(r3)		// this is pte at last
> +	l.lwz	r3,0x0(r3)		// this is pte at last
>  	/*
>  	 * if (!pte_present(pte))
>  	 */
> -	l.andi	r4,r2,0x1
> +	l.andi	r4,r3,0x1
>  	l.sfne	r4,r0			// is pte present
>  	l.bnf	d_pte_not_present
> -	l.addi	r3,r0,0xffffe3fa	// PAGE_MASK | DTLB_UP_CONVERT_MASK
> +	l.addi	r4,r0,0xffffe3fa	// PAGE_MASK | DTLB_UP_CONVERT_MASK
>  	/*
>  	 * fill DTLB TR register
>  	 */
> -	l.and	r4,r2,r3		// apply the mask
> +	l.and	r4,r3,r4		// apply the mask
>  	// Determine number of DMMU sets
> -	l.mfspr r6, r0, SPR_DMMUCFGR
> -	l.andi	r6, r6, SPR_DMMUCFGR_NTS
> -	l.srli	r6, r6, SPR_DMMUCFGR_NTS_OFF
> +	l.mfspr r2, r0, SPR_DMMUCFGR
> +	l.andi	r2, r2, SPR_DMMUCFGR_NTS
> +	l.srli	r2, r2, SPR_DMMUCFGR_NTS_OFF
>  	l.ori	r3, r0, 0x1
> -	l.sll	r3, r3, r6 	// r3 = number DMMU sets DMMUCFGR
> -	l.addi	r6, r3, -1  	// r6 = nsets mask
> -	l.and	r5, r5, r6	// calc offset:	 & (NUM_TLB_ENTRIES-1)
> +	l.sll	r3, r3, r2 	// r3 = number DMMU sets DMMUCFGR
> +	l.addi	r2, r3, -1  	// r2 = nsets mask
> +	l.mfspr	r3, r0, SPR_EEAR_BASE
> +	l.srli	r3, r3, 0xd	// >> PAGE_SHIFT
> +	l.and	r2, r3, r2	// calc offset:	 & (NUM_TLB_ENTRIES-1)
>  	                                                   //NUM_TLB_ENTRIES
> -	l.mtspr	r5,r4,SPR_DTLBTR_BASE(0)
> +	l.mtspr	r2,r4,SPR_DTLBTR_BASE(0)
>  	/*
>  	 * fill DTLB MR register
>  	 */
> -	l.mfspr	r2,r0,SPR_EEAR_BASE
> -	l.addi	r3,r0,0xffffe000	// PAGE_MASK
> -	l.and	r4,r2,r3		// apply PAGE_MASK to EA (__PHX__ do we really need this?)
> -	l.ori	r4,r4,0x1		// set hardware valid bit: DTBL_MR entry
> -	l.mtspr	r5,r4,SPR_DTLBMR_BASE(0)
> +	l.slli	r3, r3, 0xd		/* << PAGE_SHIFT => EA & PAGE_MASK */
> +	l.ori	r4,r3,0x1		// set hardware valid bit: DTBL_MR entry
> +	l.mtspr	r2,r4,SPR_DTLBMR_BASE(0)
>  
>  	EXCEPTION_LOAD_GPR2
>  	EXCEPTION_LOAD_GPR3
>  	EXCEPTION_LOAD_GPR4
> -	EXCEPTION_LOAD_GPR5
> -	EXCEPTION_LOAD_GPR6
> -	l.rfe
> -d_pmd_bad:
> -	l.nop	1
> -	EXCEPTION_LOAD_GPR2
> -	EXCEPTION_LOAD_GPR3
> -	EXCEPTION_LOAD_GPR4
> -	EXCEPTION_LOAD_GPR5
> -	EXCEPTION_LOAD_GPR6
>  	l.rfe
>  d_pmd_none:
>  d_pte_not_present:
>  	EXCEPTION_LOAD_GPR2
>  	EXCEPTION_LOAD_GPR3
>  	EXCEPTION_LOAD_GPR4
> -	EXCEPTION_LOAD_GPR5
> -	EXCEPTION_LOAD_GPR6
>  	EXCEPTION_HANDLE(_dtlb_miss_page_fault_handler)
>  
>  /* ==============================================[ ITLB miss handler ]=== */
> @@ -1077,8 +1054,6 @@ ENTRY(itlb_miss_handler)
>  	EXCEPTION_STORE_GPR2
>  	EXCEPTION_STORE_GPR3
>  	EXCEPTION_STORE_GPR4
> -	EXCEPTION_STORE_GPR5
> -	EXCEPTION_STORE_GPR6
>  	/*
>  	 * get EA of the miss
>  	 */
> @@ -1088,30 +1063,19 @@ ENTRY(itlb_miss_handler)
>  	 * pmd = (pmd_t *)(current_pgd + pgd_index(daddr));
>  	 *
>  	 */
> -	GET_CURRENT_PGD(r3,r5)		// r3 is current_pgd, r5 is temp
> +	GET_CURRENT_PGD(r3,r4)		// r3 is current_pgd, r5 is temp
>  	l.srli	r4,r2,0x18		// >> PAGE_SHIFT + (PAGE_SHIFT - 2)
>  	l.slli	r4,r4,0x2		// to get address << 2
> -	l.add	r5,r4,r3		// r4 is pgd_index(daddr)
> +	l.add	r3,r4,r3		// r4 is pgd_index(daddr)
>  	/*
>  	 * if (pmd_none(*pmd))
>  	 *   goto pmd_none:
>  	 */
> -	tophys	(r4,r5)
> +	tophys	(r4,r3)
>  	l.lwz	r3,0x0(r4)		// get *pmd value
>  	l.sfne	r3,r0
>  	l.bnf	i_pmd_none
> -	l.andi	r3,r3,0x1fff		// ~PAGE_MASK
> -	/*
> -	 * if (pmd_bad(*pmd))
> -	 *   pmd_clear(pmd)
> -	 *   goto pmd_bad:
> -	 */
> -
> -//	l.sfeq	r3,r0			// check *pmd value
> -//	l.bf	i_pmd_good
> -	l.addi	r3,r0,0xffffe000	// PAGE_MASK
> -//	l.j	i_pmd_bad
> -//	l.sw	0x0(r4),r0		// clear pmd
> +	 l.addi	r3,r0,0xffffe000	// PAGE_MASK
>  
>  i_pmd_good:
>  	/*
> @@ -1120,35 +1084,36 @@ i_pmd_good:
>  	 */
>  	l.lwz	r4,0x0(r4)		// get **pmd value
>  	l.and	r4,r4,r3		// & PAGE_MASK
> -	l.srli	r5,r2,0xd		// >> PAGE_SHIFT, r2 == EEAR
> -	l.andi	r3,r5,0x7ff		// (1UL << PAGE_SHIFT - 2) - 1
> +	l.srli	r2,r2,0xd		// >> PAGE_SHIFT, r2 == EEAR
> +	l.andi	r3,r2,0x7ff		// (1UL << PAGE_SHIFT - 2) - 1
>  	l.slli	r3,r3,0x2		// to get address << 2
>  	l.add	r3,r3,r4
> -	l.lwz	r2,0x0(r3)		// this is pte at last
> +	l.lwz	r3,0x0(r3)		// this is pte at last
>  	/*
>  	 * if (!pte_present(pte))
>  	 *
>  	 */
> -	l.andi	r4,r2,0x1
> +	l.andi	r4,r3,0x1
>  	l.sfne	r4,r0			// is pte present
>  	l.bnf	i_pte_not_present
> -	l.addi	r3,r0,0xffffe03a	// PAGE_MASK | ITLB_UP_CONVERT_MASK
> +	 l.addi	r4,r0,0xffffe03a	// PAGE_MASK | ITLB_UP_CONVERT_MASK
>  	/*
>  	 * fill ITLB TR register
>  	 */
> -	l.and	r4,r2,r3		// apply the mask
> -	l.andi	r3,r2,0x7c0		// _PAGE_EXEC | _PAGE_SRE | _PAGE_SWE |  _PAGE_URE | _PAGE_UWE
> -//	l.andi	r3,r2,0x400		// _PAGE_EXEC
> +	l.and	r4,r3,r4		// apply the mask
> +	l.andi	r3,r3,0x7c0		// _PAGE_EXEC | _PAGE_SRE | _PAGE_SWE |  _PAGE_URE | _PAGE_UWE
>  	l.sfeq	r3,r0
>  	l.bf	itlb_tr_fill //_workaround
>  	// Determine number of IMMU sets
> -	l.mfspr r6, r0, SPR_IMMUCFGR
> -	l.andi	r6, r6, SPR_IMMUCFGR_NTS
> -	l.srli	r6, r6, SPR_IMMUCFGR_NTS_OFF
> +	l.mfspr r2, r0, SPR_IMMUCFGR
> +	l.andi	r2, r2, SPR_IMMUCFGR_NTS
> +	l.srli	r2, r2, SPR_IMMUCFGR_NTS_OFF
>  	l.ori	r3, r0, 0x1
> -	l.sll	r3, r3, r6 	// r3 = number IMMU sets IMMUCFGR
> -	l.addi	r6, r3, -1  	// r6 = nsets mask
> -	l.and	r5, r5, r6	// calc offset:	 & (NUM_TLB_ENTRIES-1)
> +	l.sll	r3, r3, r2 	// r3 = number IMMU sets IMMUCFGR
> +	l.addi	r2, r3, -1  	// r2 = nsets mask
> +	l.mfspr	r3, r0, SPR_EEAR_BASE
> +	l.srli	r3, r3, 0xd	// >> PAGE_SHIFT
> +	l.and	r2, r3, r2	// calc offset:	 & (NUM_TLB_ENTRIES-1)
>  
>  /*
>   * __PHX__ :: fixme
> @@ -1160,38 +1125,24 @@ i_pmd_good:
>  itlb_tr_fill_workaround:
>  	l.ori	r4,r4,0xc0		// | (SPR_ITLBTR_UXE | ITLBTR_SXE)
>  itlb_tr_fill:
> -	l.mtspr	r5,r4,SPR_ITLBTR_BASE(0)
> +	l.mtspr	r2,r4,SPR_ITLBTR_BASE(0)
>  	/*
>  	 * fill DTLB MR register
>  	 */
> -	l.mfspr	r2,r0,SPR_EEAR_BASE
> -	l.addi	r3,r0,0xffffe000	// PAGE_MASK
> -	l.and	r4,r2,r3		// apply PAGE_MASK to EA (__PHX__ do we really need this?)
> -	l.ori	r4,r4,0x1		// set hardware valid bit: DTBL_MR entry
> -	l.mtspr	r5,r4,SPR_ITLBMR_BASE(0)
> +	l.slli	r3, r3, 0xd		/* << PAGE_SHIFT => EA & PAGE_MASK */
> +	l.ori	r4,r3,0x1		// set hardware valid bit: ITBL_MR entry
> +	l.mtspr	r2,r4,SPR_ITLBMR_BASE(0)
>  
>  	EXCEPTION_LOAD_GPR2
>  	EXCEPTION_LOAD_GPR3
>  	EXCEPTION_LOAD_GPR4
> -	EXCEPTION_LOAD_GPR5
> -	EXCEPTION_LOAD_GPR6
>  	l.rfe
>  
> -i_pmd_bad:
> -	l.nop	1
> -	EXCEPTION_LOAD_GPR2
> -	EXCEPTION_LOAD_GPR3
> -	EXCEPTION_LOAD_GPR4
> -	EXCEPTION_LOAD_GPR5
> -	EXCEPTION_LOAD_GPR6
> -	l.rfe
>  i_pmd_none:
>  i_pte_not_present:
>  	EXCEPTION_LOAD_GPR2
>  	EXCEPTION_LOAD_GPR3
>  	EXCEPTION_LOAD_GPR4
> -	EXCEPTION_LOAD_GPR5
> -	EXCEPTION_LOAD_GPR6
>  	EXCEPTION_HANDLE(_itlb_miss_page_fault_handler)
>  
>  /* ==============================================[ boot tlb handlers ]=== */
> -- 
> 1.8.1.2
> 
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