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SubjectRe: [PATCH] irqchip/gicv3-its: Avoid cache flush beyond ITS_BASERn memory size
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Hi Marc,

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

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