linux-kernel - Re: [PATCH] irqchip/gicv3-its: Avoid cache flush beyond ITS

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Message-ID: <20160216083549.5c889627@arm.com>
Date:	Tue, 16 Feb 2016 08:35:49 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Shanker Donthineni <shankerd@...eaurora.org>
Cc:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Vikram Sethi <vikrams@...eaurora.org>,
	Jason Cooper <jason@...edaemon.net>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] irqchip/gicv3-its: Avoid cache flush beyond ITS_BASERn
 memory size

On Mon, 15 Feb 2016 21:41:52 -0600
Shanker Donthineni <shankerd@...eaurora.org> wrote:

> Function its_alloc_tables() maintains two local variables, "order" and
> and "alloc_size", to hold memory size that has been allocated to
> ITS_BASEn. We don't always refresh the variable alloc_size whenever
> value of the variable order changes, causing the following two problems.
> 
>   - Cache flush operation with size more than required.
>   - Information reported by pr_info is not correct.
> 
> Use a helper macro that converts page order to size in bytes instead of
> variable "alloc_size" to fix both the problems.
> 
> Signed-off-by: Shanker Donthineni <shankerd@...eaurora.org>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 0a73632..6f717f7 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -78,6 +78,9 @@ struct its_node {
>  
>  #define ITS_ITT_ALIGN		SZ_256
>  
> +/* Convert page order to size in bytes */
> +#define PAGE_ORDER_TO_BYTES(o)	(PAGE_SIZE << (o))
> +

nit: PAGE_ORDER_TO_size() seems more appropriate.

>  struct event_lpi_map {
>  	unsigned long		*lpi_map;
>  	u16			*col_map;
> @@ -846,7 +849,6 @@ static int its_alloc_tables(const char *node_name, struct its_node *its)
>  		u64 type = GITS_BASER_TYPE(val);
>  		u64 entry_size = GITS_BASER_ENTRY_SIZE(val);
>  		int order = get_order(psz);
> -		int alloc_size;
>  		int alloc_pages;
>  		u64 tmp;
>  		void *base;
> @@ -878,9 +880,8 @@ static int its_alloc_tables(const char *node_name, struct its_node *its)
>  			}
>  		}
>  
> -		alloc_size = (1 << order) * PAGE_SIZE;
>  retry_alloc_baser:
> -		alloc_pages = (alloc_size / psz);
> +		alloc_pages = (PAGE_ORDER_TO_BYTES(order) / psz);
>  		if (alloc_pages > GITS_BASER_PAGES_MAX) {
>  			alloc_pages = GITS_BASER_PAGES_MAX;
>  			order = get_order(GITS_BASER_PAGES_MAX * psz);
> @@ -933,7 +934,8 @@ retry_baser:
>  			shr = tmp & GITS_BASER_SHAREABILITY_MASK;
>  			if (!shr) {
>  				cache = GITS_BASER_nC;
> -				__flush_dcache_area(base, alloc_size);
> +				__flush_dcache_area(base,
> +						    PAGE_ORDER_TO_BYTES(order));

Please keep it on the same line. It helps my random grepping...

>  			}
>  			goto retry_baser;
>  		}
> @@ -966,7 +968,7 @@ retry_baser:
>  		}
>  
>  		pr_info("ITS: allocated %d %s @%lx (psz %dK, shr %d)\n",
> -			(int)(alloc_size / entry_size),
> +			(int)(PAGE_ORDER_TO_BYTES(order) / entry_size),
>  			its_base_type_string[type],
>  			(unsigned long)virt_to_phys(base),
>  			psz / SZ_1K, (int)shr >> GITS_BASER_SHAREABILITY_SHIFT);


Otherwise looks good.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.