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SubjectRe: [PATCH] irqchip/gic-v4: Fix non-stick page size error for setup GITS_BASER
Hi Shaokun,

On 2020-03-16 05:48, Shaokun Zhang wrote:
> Hi Marc,
>
> On 2020/3/13 20:00, Marc Zyngier wrote:
>> Shaokun, Nianyao,
>>
>> On 2020-03-13 08:46, Shaokun Zhang wrote:
>>> From: Nianyao Tang <tangnianyao@huawei.com>
>>>
>>> There is an error when ITS is probed if hw GITS_BASER<2>
>>> only supports psz=SZ_16K while GITS_BASER<1> only supports psz=SZ_4K.
>>> In its_alloc_tables, it has updated GITS_BASER<1>.psz and uses
>>> psz=SZ_4K for setup GITS_BASER<2>, and would fail in writing
>>> GITS_BASER<2>.psz=SZ_4K. 4K PAGE is the smallest and shall stop retry
>>> for other page sizes.
>>>
>>> That latter GITS_BASER<n>.psz is larger than former, will lead
>>> to similar error.
>>>
>>> [ 0.000000] ITS@0x0000000660000000: Virtual CPUs doesn't stick:
>>> ba1f0824404004ff ba1f0824404005ff
>>> [ 0.000000] ITS@0x0000000660000000: failed probing (-6)
>>> [ 0.000000] ITS: No ITS available, not enabling LPIs
>>>
>>> From GIC SPEC document, it's allowed for this implematation, the
>>> latter
>>> GITS_BASER<n>.psz is larger than the former.
>>
>> I was really hoping nobody would build an ITS with disjoint sets of
>> page sizes. Oh well...
>>
>>> Let's fix this error with following patch.
>>>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: Marc Zyngier <maz@kernel.org>
>>> Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
>>> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
>>> ---
>>> drivers/irqchip/irq-gic-v3-its.c | 1 -
>>> 1 file changed, 1 deletion(-)
>>>
>>> diff --git a/drivers/irqchip/irq-gic-v3-its.c
>>> b/drivers/irqchip/irq-gic-v3-its.c
>>> index 83b1186..59bf8d6 100644
>>> --- a/drivers/irqchip/irq-gic-v3-its.c
>>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>>> @@ -2341,7 +2341,6 @@ static int its_alloc_tables(struct its_node
>>> *its)
>>> }
>>>
>>> /* Update settings which will be used for next BASERn */
>>> - psz = baser->psz;
>>> cache = baser->val & GITS_BASER_CACHEABILITY_MASK;
>>> shr = baser->val & GITS_BASER_SHAREABILITY_MASK;
>>> }
>>
>> I think this just papers over the problem, and I'd rather tackle it
>> fully
>> by forcing the probe of the supported page sizes for each GITS_BASERn
>> register. See the patch below (which I've only boot-tested once on
>> pretty
>> standard HW as well as a guest).
>>
>> This, in turn, simplifies the way we perform the allocation (no nested
>> retry loop). This is of course a much more patch invasive, but at
>> least
>> it doesn't leave too much cruft behind.
>>
>> Please let me know whether this solves your issue.
>>
>
> Thanks your quick reply.
> With your following fixed patch, it can work for Nianyao, So:
> Tested-by: Nianyao Tang <tangnianyao@huawei.com>

Thanks for the quick feedback. I've now added this patch to the 5.7
queue.

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

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