Re: [PATCH] irqchip/gicv3-its: Avoid cache flush beyond ITS_BASERn memory size

[Shanker Donthineni]

Hi Marc,

On 02/16/2016 02:35 AM, Marc Zyngier wrote:
> On Mon, 15 Feb 2016 21:41:52 -0600
> Shanker Donthineni <shankerd@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
> > ---
> >   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.

I will change to PAGE_ORDER_TO_SIZE in v2 patch.

> >   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...

Sure, I will keep it on the same line in v2 patch.

> >   			}
> >   			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.