linux-kernel - Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern

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Message-ID: <20131008073301.GC10669@dhcp-26-207.brq.redhat.com>
Date:	Tue, 8 Oct 2013 09:33:02 +0200
From:	Alexander Gordeev <agordeev@...hat.com>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Andy King <acking@...are.com>, Jon Mason <jon.mason@...el.com>,
	Matt Porter <mporter@...nel.crashing.org>,
	linux-pci@...r.kernel.org, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux390@...ibm.com,
	linux-s390@...r.kernel.org, x86@...nel.org,
	linux-ide@...r.kernel.org, iss_storagedev@...com,
	linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	linux-driver@...gic.com,
	Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
	"VMware, Inc." <pv-drivers@...are.com>, linux-scsi@...r.kernel.org
Subject: Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement
 pattern

On Tue, Oct 08, 2013 at 03:33:30PM +1100, Michael Ellerman wrote:
> On Wed, Oct 02, 2013 at 12:29:04PM +0200, Alexander Gordeev wrote:
> > This technique proved to be confusing and error-prone. Vast share
> > of device drivers simply fail to follow the described guidelines.
> 
> To clarify "Vast share of device drivers":
> 
>  - 58 drivers call pci_enable_msix()
>  - 24 try a single allocation and then fallback to MSI/LSI
>  - 19 use the loop style allocation as above
>  - 14 try an allocation, and if it fails retry once
>  - 1  incorrectly continues when pci_enable_msix() returns > 0
> 
> So 33 drivers (> 50%) successfully make use of the "confusing and
> error-prone" return value.

Ok, you caught me - 'vast share' is incorrect and is a subject to
rewording. But out of 19/58 how many drivers tested fallbacks on the
real hardware? IOW, which drivers are affected by the pSeries quota?

> And yes, one is buggy, so obviously the interface is too complex. Thanks
> drivers/ntb/ntb_hw.c

vmxnet3 would be the best example.

> cheers

-- 
Regards,
Alexander Gordeev
agordeev@...hat.com
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