lkml.org 
[lkml]   [2019]   [Sep]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 10/35] irqchip/gic-v4.1: VPE table (aka GICR_VPROPBASER) allocation
From
Date
On 2019/9/27 0:27, Marc Zyngier wrote:
> On 26/09/2019 16:57, Marc Zyngier wrote:
>> On 26/09/2019 16:19, Zenghui Yu wrote:
>>> Hi Marc,
>>>
>>> Two more questions below.
>>>
>>> On 2019/9/25 22:41, Marc Zyngier wrote:
>>>> On 25/09/2019 14:04, Zenghui Yu wrote:
>>>>> Hi Marc,
>>>>>
>>>>> Some questions about this patch, mostly to confirm that I would
>>>>> understand things here correctly.
>>>>>
>>>>> On 2019/9/24 2:25, Marc Zyngier wrote:
>>>>>> GICv4.1 defines a new VPE table that is potentially shared between
>>>>>> both the ITSs and the redistributors, following complicated affinity
>>>>>> rules.
>>>>>>
>>>>>> To make things more confusing, the programming of this table at
>>>>>> the redistributor level is reusing the GICv4.0 GICR_VPROPBASER register
>>>>>> for something completely different.
>>>>>>
>>>>>> The code flow is somewhat complexified by the need to respect the
>>>>>> affinities required by the HW, meaning that tables can either be
>>>>>> inherited from a previously discovered ITS or redistributor.
>>>>>>
>>>>>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>>>>>> ---
>>>>>
>>>>> [...]
>>>>>
>>>>>> @@ -1962,6 +1965,65 @@ static bool its_parse_indirect_baser(struct its_node *its,
>>>>>> return indirect;
>>>>>> }
>>>>>>
>>>>>> +static u32 compute_common_aff(u64 val)
>>>>>> +{
>>>>>> + u32 aff, clpiaff;
>>>>>> +
>>>>>> + aff = FIELD_GET(GICR_TYPER_AFFINITY, val);
>>>>>> + clpiaff = FIELD_GET(GICR_TYPER_COMMON_LPI_AFF, val);
>>>>>> +
>>>>>> + return aff & ~(GENMASK(31, 0) >> (clpiaff * 8));
>>>>>> +}
>>>>>> +
>>>>>> +static u32 compute_its_aff(struct its_node *its)
>>>>>> +{
>>>>>> + u64 val;
>>>>>> + u32 svpet;
>>>>>> +
>>>>>> + /*
>>>>>> + * Reencode the ITS SVPET and MPIDR as a GICR_TYPER, and compute
>>>>>> + * the resulting affinity. We then use that to see if this match
>>>>>> + * our own affinity.
>>>>>> + */
>>>>>> + svpet = FIELD_GET(GITS_TYPER_SVPET, its->typer);
>>>
>>> The spec says, ITS does not share vPE table with Redistributors when
>>> SVPET==0. It seems that we miss this rule and simply regard SVPET as
>>> GICR_TYPER_COMMON_LPI_AFF here. Am I wrong?
>>
>> Correct. I missed the case where the ITS doesn't share anything. That's
>> pretty unlikely though (you loose all the benefit of v4.1, and I don't
>> really see how you'd make it work reliably).
>
> Actually, this is already handled...
>
>>
>>>
>>>>>> + val = FIELD_PREP(GICR_TYPER_COMMON_LPI_AFF, svpet);
>>>>>> + val |= FIELD_PREP(GICR_TYPER_AFFINITY, its->mpidr);
>>>>>> + return compute_common_aff(val);
>>>>>> +}
>>>>>> +
>>>>>> +static struct its_node *find_sibbling_its(struct its_node *cur_its)
>>>>>> +{
>>>>>> + struct its_node *its;
>>>>>> + u32 aff;
>>>>>> +
>>>>>> + if (!FIELD_GET(GITS_TYPER_SVPET, cur_its->typer))
>>>>>> + return NULL;
>
> ... here. If SVPET is 0, there is no sibling, and we'll allocate a VPE
> table as usual.

Yes, I see. So we can safely encode the non-zero SVPET as
COMMON_LPI_AFF in a GICR_TYPER when computing the affinity.


Thanks,
zenghui

\
 
 \ /
  Last update: 2019-09-27 04:04    [W:0.059 / U:2.564 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site