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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Keith Busch <keith.busch@intel.com>, Jens Axboe <axboe@fb.com>,
	linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH 2/2] nvme pci: try to allocate multiple irq vectors again in case of -EINVAL
Date: Thu, 27 Dec 2018 14:08:34 +0100	[thread overview]
Message-ID: <20181227130834.GA22967@lst.de> (raw)
In-Reply-To: <20181227082136.GA14423@ming.t460p>

On Thu, Dec 27, 2018 at 04:21:38PM +0800, Ming Lei wrote:
> On Wed, Dec 26, 2018 at 07:20:27PM +0100, Christoph Hellwig wrote:
> > On Wed, Dec 26, 2018 at 06:37:55PM +0800, Ming Lei wrote:
> > > It is observed on QEMU that pci_alloc_irq_vectors_affinity() may
> > > returns -EINVAL when the requested number is too big(such as 64).
> > 
> > Which is not how this API is supposed to work and documented to work.
> > 
> > We need to fix pci_alloc_irq_vectors_affinity to not return a spurious
> > error and just return the allocated number of vectors instead of
> > hacking around that in drivers.
> 
> Yeah, you are right.
> 
> The issue is that QEMU nvme-pci is MSIX-capable only, and hasn't MSI
> capability.
> 
> __pci_enable_msix_range() actually returns -ENOSPC, but __pci_enable_msi_range()
> returns -EINVAL because dev->msi_cap is zero.
> 
> Maybe we need the following fix?

Should it matter?  We still get a negative vecs back, and still fall
back to the next option.  Unless ther are no irqs available at all
for the selected types pci_alloc_irq_vectors_affinity should never
return an error.

  reply	other threads:[~2018-12-27 13:08 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20181226103755.2101-1-ming.lei@redhat.com>
     [not found] ` <20181226103755.2101-3-ming.lei@redhat.com>
     [not found]   ` <20181226182027.GA5866@lst.de>
2018-12-27  8:21     ` [PATCH 2/2] nvme pci: try to allocate multiple irq vectors again in case of -EINVAL Ming Lei
2018-12-27 13:08       ` Christoph Hellwig [this message]
2018-12-27 22:16         ` Ming Lei
2018-12-31 21:51         ` Bjorn Helgaas

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