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Subject: Re: [PATCH] irqchip/gic-v3-its: cap lpi_id_bits to reduce memory
 footprint
To:     Marc Zyngier <marc.zyngier@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Jason Cooper <jason@lakedaemon.net>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        Jia He <jia.he@hxt-semitech.com>
References: <1535432006-2304-1-git-send-email-jia.he@hxt-semitech.com>
 <865zzuyijp.wl-marc.zyngier@arm.com>
From:   Jia He <hejianet@gmail.com>
Message-ID: <a28b854e-3bc9-0c10-2faf-63e4d44ec14b@gmail.com>
Date:   Tue, 28 Aug 2018 20:08:04 +0800
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On 8/28/2018 4:58 PM, Marc Zyngier Wrote:
> On Tue, 28 Aug 2018 05:53:26 +0100,
> Jia He <hejianet@gmail.com> wrote:
>>
>> In commit fe8e93504ce8 ("irqchip/gic-v3-its: Use full range of LPIs"),
>> it removes the cap for lpi_id_bits. But it will cause more pointless
>> memory footprint.
>>
>> There is a WARN_ON when my QDF2400 server boots up (pagesize is 4k)
>> ============begin===============
> 
> [trimming not-so-useful trace]
> 
>> ============end============
>>
>> In its_alloc_lpi_tables, lpi_id_bits is 24 in QDF2400. Then
>> its_allocate_prop_table will try to allocate 16M(order 12 if
>> pagesize=4k). Thus it causes the WARN_ON.
>>
>> As said by Marc,
>> Capping lpi_id_bits at 16 (which is what we had before) is plenty,
>> will save a some memory, and gives some margin before we need to push
>> it up again.
>>
>> This patch re-caps the lpi_id_bits.
>>
>> Fixes: fe8e93504ce8 ("irqchip/gic-v3-its: Use full range of LPIs")
>> Signed-off-by: Jia He <jia.he@hxt-semitech.com>
>> Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
> 
> Thanks for doing this. Small problem with this patch:
> 
> The email comes from hejianet@gmail.com, while the sign off is by
> jia.he@hxt-semitech.com. Your email should start with a:
> 
> 	From: Jia He <jia.he@hxt-semitech.com>
> 

Thanks for the pointing. And sorry for that problem.

---
Cheers,
Jia
> Other than that:
> 
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> 
> Thomas, would you mind picking this up so that it gets into the next
> convenient -rc?
> 
> Thanks,
> 
> 	M. (/me goes back hiking...)
> 	
>