linux-kernel - Re: [PATCH] irq/gic-its: gicv4: set VPENDING table as inner-shareable

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Date:   Mon, 2 Dec 2019 19:07:58 +0800
From:   Guoheyi <guoheyi@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <wanghaibin.wang@...wei.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH] irq/gic-its: gicv4: set VPENDING table as inner-shareable


在 2019/12/2 2:04, Marc Zyngier 写道:
> On Sat, 30 Nov 2019 15:38:49 +0800
> Heyi Guo <guoheyi@...wei.com> wrote:
>
>> There is no special reason to set virtual LPI pending table as
>> non-shareable. If we choose to hard code the shareability without
>> probing, inner-shareable will be a better choice, for all the other
>> ITS/GICR tables prefer to be inner-shareable.
> One of the issues is that we have strictly no idea what the caches are
> Inner Shareable with (I've been asking for such clarification for years
> without getting anywhere). You can have as many disconnected inner
> shareable domains as you want!

Hisilicon HIP07 and HIP08 are compliant with ARM SBSA and have only one 
inner shareable domain in the whole system.

What will happen if a system has multiple inner shareable domains? Will 
Linux still work on such system? Can we declare that Linux only supports 
one single inner shareable domain?

>
> I suspect that in the grand scheme of things, the redistributors
> ought to be in the same inner shareable domain, and that with a bit of
> luck, the CPUs are there as well. Still, that's a massive guess.
>
>> What's more, on Hisilicon hip08 it will trigger some kind of bus
>> warning when mixing use of different shareabilities.
> Do you have more information about what the bus is complaining about?
> Is that because the CPUs have these pages mapped as inner shareable?

Actually HIP08 L3 Cache will complain on any non-shareable cache entry, 
for the data coherence cannot be guarenteed for such configuration. This 
also implies VPENDING table will be allocated and snooped in L3 cache.

>
> I'll give it a go on D05 (HIP07) to find out what changes there.

Thanks,

HG

>
> Thanks,
>
> 	M.
>
>> Signed-off-by: Heyi Guo <guoheyi@...wei.com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Jason Cooper <jason@...edaemon.net>
>> Cc: Marc Zyngier <maz@...nel.org>
>> ---
>>   drivers/irqchip/irq-gic-v3-its.c   | 2 +-
>>   include/linux/irqchip/arm-gic-v3.h | 3 +++
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
>> index 787e8eec9a7f..d31e863bc9ef 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -2831,7 +2831,7 @@ static void its_vpe_schedule(struct its_vpe *vpe)
>>   	val  = virt_to_phys(page_address(vpe->vpt_page)) &
>>   		GENMASK_ULL(51, 16);
>>   	val |= GICR_VPENDBASER_RaWaWb;
>> -	val |= GICR_VPENDBASER_NonShareable;
>> +	val |= GICR_VPENDBASER_InnerShareable;
>>   	/*
>>   	 * There is no good way of finding out if the pending table is
>>   	 * empty as we can race against the doorbell interrupt very
>> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
>> index 5cc10cf7cb3e..a184f875e451 100644
>> --- a/include/linux/irqchip/arm-gic-v3.h
>> +++ b/include/linux/irqchip/arm-gic-v3.h
>> @@ -289,6 +289,9 @@
>>   #define GICR_VPENDBASER_NonShareable					\
>>   	GIC_BASER_SHAREABILITY(GICR_VPENDBASER, NonShareable)
>>   
>> +#define GICR_VPENDBASER_InnerShareable					\
>> +	GIC_BASER_SHAREABILITY(GICR_VPENDBASER, InnerShareable)
>> +
>>   #define GICR_VPENDBASER_nCnB	GIC_BASER_CACHEABILITY(GICR_VPENDBASER, INNER, nCnB)
>>   #define GICR_VPENDBASER_nC 	GIC_BASER_CACHEABILITY(GICR_VPENDBASER, INNER, nC)
>>   #define GICR_VPENDBASER_RaWt	GIC_BASER_CACHEABILITY(GICR_VPENDBASER, INNER, RaWt)
>
>