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Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between p
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev |
Date: |
Thu, 6 Nov 2014 11:26:05 +0200 |
On Thu, Nov 06, 2014 at 10:20:32AM +0100, Markus Armbruster wrote:
> SeokYeon Hwang <address@hidden> writes:
>
> >> -----Original Message-----
> >> From: Paolo Bonzini [mailto:address@hidden On Behalf Of Paolo
> >> Bonzini
> >> Sent: Wednesday, November 05, 2014 11:55 PM
> >> To: Michael S. Tsirkin
> >> Cc: Markus Armbruster; SeokYeon Hwang; address@hidden
> >> Subject: Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling
> >> between pci_qdev_init() and qdev
> >>
> >>
> >>
> >> On 05/11/2014 14:28, Michael S. Tsirkin wrote:
> >> > > I think bypassing the question by converting to realize makes the
> >> > > most sense...
> >> >
> >> > I'm fine with doing that but Markus's patches wouldn't yet have solved
> >> > the problem by themselves since init is still around, right?
> >> >
> >> > This probably means fixing this bug can't justify merging the realize
> >> > patchset after freeze.
> >>
> >> Yes, I agree. I meant that the API is not very well defined. I would
> >> handle everything else on a case-by-case basis, by reviewing each init
> >> function that is converted to realize.
> >>
> >> Since the patch was for an out-of-tree device, it can wait for 2.3 anyway.
> >>
> >> Paolo
> >
> > I cannot fully understand your conversation.
>
> You appear to have a PCIDeviceClass method init() returning a positive
> value. Doesn't work. Only values <= 0 do.
>
> Your proposed fix is to make its caller treat a positive value like a
> negative one.
>
> Paolo points out that init()'s contract is unclear. His preferred way
> of clarifying it is to convert PCI from init() to realize(), which has a
> sufficiently clear contract.
>
> Doesn't help you now. My "pci: Partial conversion to realize" series,
> will help you once it lands, but only if you convert your device.
>
> You obviously want a solution earlier. The one you proposed implicitly
> clarifies the PCIDeviceClass init() contract to "zero means success,
> anything else failure". I don't think that's a good idea, because it
> makes PCIDeviceClass's init() differ from DeviceClass's. There,
> non-negative value means success, negative means failure (see
> device_realize()).
>
> Fix your device not to return positive values instead.
>
> You could additionally fix pci_qdev_init() to treat positive numbers as
> success, for consistency with device_realize(), but that requires
> auditing all existing PCIDeviceClass init() methods. Waste of your
> time, because they all go away when we convert to realize().
>
> > But, I think this patch is still worth before all 'init()' convert to
> > 'realize()'.
> > Moreover, It has no side effect at all.
>
> I don't like it, because it makes PCIDeviceClass's init() inconsistent
> with DeviceClass's.
I agree with Markus here. A positive return value should not indicate an
error.
--
MST
- [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, SeokYeon Hwang, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Paolo Bonzini, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Michael S. Tsirkin, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Markus Armbruster, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Paolo Bonzini, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Michael S. Tsirkin, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Paolo Bonzini, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, SeokYeon Hwang, 2014/11/05
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Markus Armbruster, 2014/11/06
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, SeokYeon Hwang, 2014/11/06
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Michael S. Tsirkin, 2014/11/06
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, SeokYeon Hwang, 2014/11/06
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Markus Armbruster, 2014/11/07
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, SeokYeon Hwang, 2014/11/10
- Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, Markus Armbruster, 2014/11/10
Re: [Qemu-devel] [PATCH] pci: fixed mismatch of error-handling between pci_qdev_init() and qdev, SeokYeon Hwang, 2014/11/05