linux-kernel - Re: [PATCH v2 13/13] MIPS: mm: Panic if an XPA kernel is run without RIXI

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Message-ID: <20160418100446.GN7859@jhogan-linux.le.imgtec.org>
Date:	Mon, 18 Apr 2016 11:04:47 +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>,
	"Paul Gortmaker" <paul.gortmaker@...driver.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 13/13] MIPS: mm: Panic if an XPA kernel is run without
 RIXI

On Mon, Apr 18, 2016 at 10:35:33AM +0100, Paul Burton wrote:
> XPA kernels hardcode for the presence of RIXI - the PTE format & its
> handling presume RI & XI bits. Make this dependence explicit by panicing
> if we run on a system that violates it.
> 
> Signed-off-by: Paul Burton <paul.burton@...tec.com>
> 
> ---
> 
> Changes in v2:
> - New patch, in response to clarification on patch 5.
> 
>  arch/mips/mm/tlbex.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
> index 3f1a8a2..9c39c66 100644
> --- a/arch/mips/mm/tlbex.c
> +++ b/arch/mips/mm/tlbex.c
> @@ -2395,6 +2395,9 @@ void build_tlb_refill_handler(void)
>  	 */
>  	static int run_once = 0;
>  
> +	if (config_enabled(CONFIG_XPA) && !cpu_has_rixi)
> +		panic("Kernels supporting XPA currently require CPUs with RIXI\n");

Don't think you need the newline.

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

In the future we can hopefully drop that requirement so that XPA kernels
can run on non-XPA, non-RIXI hardware.

Cheers
James

> +
>  	output_pgtable_bits_defines();
>  	check_pabits();
>  
> -- 
> 2.8.0
> 

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