linux-kernel - Re: [PATCH 09/12] MIPS: mm: Pass scratch register through to iPTE

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Date:	Fri, 15 Apr 2016 23:28:54 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	Paul Burton <paul.burton@...tec.com>
CC:	<linux-mips@...ux-mips.org>, Ralf Baechle <ralf@...ux-mips.org>,
	"Adam Buchbinder" <adam.buchbinder@...il.com>,
	Huacai Chen <chenhc@...ote.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	<linux-kernel@...r.kernel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH 09/12] MIPS: mm: Pass scratch register through to iPTE_SW

On Fri, Apr 15, 2016 at 11:36:57AM +0100, Paul Burton wrote:
> Rather than hardcode a scratch register for the XPA case in iPTE_SW,
> pass one through from the work registers allocated by the caller. This
> allows for the XPA path to function correctly regardless of the work
> registers in use.

Looks good to me, although probably worth mentioning that the current
behaviour uses the $1 register, so this fixes another case of $1
clobbering.

Reviewed-by: James Hogan <james.hogan@...tec.com>

Cheers
James

> 
> Signed-off-by: Paul Burton <paul.burton@...tec.com>
> ---
> 
>  arch/mips/mm/tlbex.c | 24 +++++++++++-------------
>  1 file changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
> index 004cd9f..d7a7b3d 100644
> --- a/arch/mips/mm/tlbex.c
> +++ b/arch/mips/mm/tlbex.c
> @@ -1526,14 +1526,12 @@ iPTE_LW(u32 **p, unsigned int pte, unsigned int ptr)
>  
>  static void
>  iPTE_SW(u32 **p, struct uasm_reloc **r, unsigned int pte, unsigned int ptr,
> -	unsigned int mode)
> +	unsigned int mode, unsigned int scratch)
>  {
>  #ifdef CONFIG_PHYS_ADDR_T_64BIT
>  	unsigned int hwmode = mode & (_PAGE_VALID | _PAGE_DIRTY);
>  
>  	if (config_enabled(CONFIG_XPA) && !cpu_has_64bits) {
> -		const int scratch = 1; /* Our extra working register */
> -
>  		uasm_i_lui(p, scratch, (mode >> 16));
>  		uasm_i_or(p, pte, pte, scratch);
>  	} else
> @@ -1630,11 +1628,11 @@ build_pte_present(u32 **p, struct uasm_reloc **r,
>  /* Make PTE valid, store result in PTR. */
>  static void
>  build_make_valid(u32 **p, struct uasm_reloc **r, unsigned int pte,
> -		 unsigned int ptr)
> +		 unsigned int ptr, unsigned int scratch)
>  {
>  	unsigned int mode = _PAGE_VALID | _PAGE_ACCESSED;
>  
> -	iPTE_SW(p, r, pte, ptr, mode);
> +	iPTE_SW(p, r, pte, ptr, mode, scratch);
>  }
>  
>  /*
> @@ -1670,12 +1668,12 @@ build_pte_writable(u32 **p, struct uasm_reloc **r,
>   */
>  static void
>  build_make_write(u32 **p, struct uasm_reloc **r, unsigned int pte,
> -		 unsigned int ptr)
> +		 unsigned int ptr, unsigned int scratch)
>  {
>  	unsigned int mode = (_PAGE_ACCESSED | _PAGE_MODIFIED | _PAGE_VALID
>  			     | _PAGE_DIRTY);
>  
> -	iPTE_SW(p, r, pte, ptr, mode);
> +	iPTE_SW(p, r, pte, ptr, mode, scratch);
>  }
>  
>  /*
> @@ -1780,7 +1778,7 @@ static void build_r3000_tlb_load_handler(void)
>  	build_r3000_tlbchange_handler_head(&p, K0, K1);
>  	build_pte_present(&p, &r, K0, K1, -1, label_nopage_tlbl);
>  	uasm_i_nop(&p); /* load delay */
> -	build_make_valid(&p, &r, K0, K1);
> +	build_make_valid(&p, &r, K0, K1, -1);
>  	build_r3000_tlb_reload_write(&p, &l, &r, K0, K1);
>  
>  	uasm_l_nopage_tlbl(&l, p);
> @@ -1811,7 +1809,7 @@ static void build_r3000_tlb_store_handler(void)
>  	build_r3000_tlbchange_handler_head(&p, K0, K1);
>  	build_pte_writable(&p, &r, K0, K1, -1, label_nopage_tlbs);
>  	uasm_i_nop(&p); /* load delay */
> -	build_make_write(&p, &r, K0, K1);
> +	build_make_write(&p, &r, K0, K1, -1);
>  	build_r3000_tlb_reload_write(&p, &l, &r, K0, K1);
>  
>  	uasm_l_nopage_tlbs(&l, p);
> @@ -1842,7 +1840,7 @@ static void build_r3000_tlb_modify_handler(void)
>  	build_r3000_tlbchange_handler_head(&p, K0, K1);
>  	build_pte_modifiable(&p, &r, K0, K1,  -1, label_nopage_tlbm);
>  	uasm_i_nop(&p); /* load delay */
> -	build_make_write(&p, &r, K0, K1);
> +	build_make_write(&p, &r, K0, K1, -1);
>  	build_r3000_pte_reload_tlbwi(&p, K0, K1);
>  
>  	uasm_l_nopage_tlbm(&l, p);
> @@ -2010,7 +2008,7 @@ static void build_r4000_tlb_load_handler(void)
>  		}
>  		uasm_l_tlbl_goaround1(&l, p);
>  	}
> -	build_make_valid(&p, &r, wr.r1, wr.r2);
> +	build_make_valid(&p, &r, wr.r1, wr.r2, wr.r3);
>  	build_r4000_tlbchange_handler_tail(&p, &l, &r, wr.r1, wr.r2);
>  
>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
> @@ -2124,7 +2122,7 @@ static void build_r4000_tlb_store_handler(void)
>  	build_pte_writable(&p, &r, wr.r1, wr.r2, wr.r3, label_nopage_tlbs);
>  	if (m4kc_tlbp_war())
>  		build_tlb_probe_entry(&p);
> -	build_make_write(&p, &r, wr.r1, wr.r2);
> +	build_make_write(&p, &r, wr.r1, wr.r2, wr.r3);
>  	build_r4000_tlbchange_handler_tail(&p, &l, &r, wr.r1, wr.r2);
>  
>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
> @@ -2180,7 +2178,7 @@ static void build_r4000_tlb_modify_handler(void)
>  	if (m4kc_tlbp_war())
>  		build_tlb_probe_entry(&p);
>  	/* Present and writable bits set, set accessed and dirty bits. */
> -	build_make_write(&p, &r, wr.r1, wr.r2);
> +	build_make_write(&p, &r, wr.r1, wr.r2, wr.r3);
>  	build_r4000_tlbchange_handler_tail(&p, &l, &r, wr.r1, wr.r2);
>  
>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
> -- 
> 2.8.0
> 

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