linux-kernel - Re: [PATCH] msi-x: let drivers retry when not enough vectors

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Date:	Thu, 7 May 2009 03:27:31 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Sheng Yang <sheng@...ux.intel.com>
Cc:	kvm@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
	jbarnes@...tuousgeek.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, Matthew Wilcox <willy@...ux.intel.com>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] msi-x: let drivers retry when not enough vectors

On Thu, May 07, 2009 at 04:51:24PM +0800, Sheng Yang wrote:
> On Thursday 07 May 2009 16:28:41 Michael S. Tsirkin wrote:
> > pci_enable_msix currently returns -EINVAL if you ask
> > for more vectors than supported by the device, which would
> > typically cause fallback to regular interrupts.
> >
> > It's better to return the table size, making the driver retry
> > MSI-X with less vectors.
> 
> Hi Michael
> 
> I think driver should read from capability list to know how many vector 
> supported by this device before enable MSI-X for device, as 
> pci_msix_table_size() did...

I think Michael's patch makes sense.  It reduces the amount of work the
driver has to do without requiring any additional work in the core.  I
don't see the disadvantage to it.

Reviewed-by: Matthew Wilcox <willy@...ux.intel.com>

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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