linux-kernel - Re: [PATCH v12 02/11] genirq/msi: msi

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Date:	Wed, 10 Aug 2016 10:48:02 +0200
From:	Auger Eric <eric.auger@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	eric.auger.pro@...il.com, christoffer.dall@...aro.org,
	marc.zyngier@....com, robin.murphy@....com,
	alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
	jason@...edaemon.net, linux-arm-kernel@...ts.infradead.org,
	kvm@...r.kernel.org, drjones@...hat.com,
	linux-kernel@...r.kernel.org, Bharat.Bhushan@...escale.com,
	pranav.sawargaonkar@...il.com, p.fedin@...sung.com,
	iommu@...ts.linux-foundation.org, Jean-Philippe.Brucker@....com,
	yehuday@...vell.com, Manish.Jaggi@...iumnetworks.com,
	robert.richter@...iumnetworks.com, dennis.chen@....com
Subject: Re: [PATCH v12 02/11] genirq/msi: msi_compose wrapper

Hi Thomas,

On 09/08/2016 11:19, Thomas Gleixner wrote:
> On Tue, 2 Aug 2016, Eric Auger wrote:
> 
>> Currently the MSI message is composed by directly calling
>> irq_chip_compose_msi_msg and erased by setting the memory to zero.
>>
>> On some platforms, we will need to complexify this composition to
>> properly handle MSI emission through IOMMU. Also we will need to track
>> when the MSI message is erased.
> 
> I just can't find how you do that. After applying the series the
> 
>> +	if (erase)
>> +		memset(msg, 0, sizeof(*msg));
> 
> branch is still just a memset(). The wrapper is fine for the compose side, but
> having the extra argument just to wrap the memset() for no gain is silly.

Yes you're right: this was true in the first releases of the series
where the iommu mapping/unmapping were done at composition & erase time.
Now the mapping/unmapping is done on msi_domain_alloc/free_irqs, this is
not mandated anymore. I will keep the wrapper for the compose side and
remove the rest + update the commit message accordingly.

Thank you for your time.

Eric
> 
> Thanks,
> 
> 	tglx
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