Re: [Qemu-devel] [PATCH 2/7] megasas: Enable MSI-X support

[Hannes Reinecke]

On 04/17/2014 02:07 PM, Andreas Färber wrote:
> Am 17.04.2014 08:20, schrieb Hannes Reinecke:
>> On 04/16/2014 07:52 PM, Michael S. Tsirkin wrote:
>>> On Wed, Apr 16, 2014 at 07:47:37PM +0200, Andreas Färber wrote:
>>>> Am 16.04.2014 19:40, schrieb Michael S. Tsirkin:
>>>>> On Wed, Apr 16, 2014 at 06:48:08PM +0200, Andreas Färber wrote:
>>>>>> Am 16.04.2014 18:32, schrieb Alexander Graf:
>>>>>>>
>>>>>>> On 16.04.14 16:44, Hannes Reinecke wrote:
>>>>>>>> MSI-X support has been fixed in qemu, so we can enable it again.
>>>>>>>>
>>>>>>>> Signed-off-by: Hannes Reinecke <address@hidden>
>>>>>>>> ---
>>>>>>>>   hw/scsi/megasas.c | 19 ++++++-------------
>>>>>>>>   1 file changed, 6 insertions(+), 13 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
>>>>>>>> index 1781525..df45286 100644
>>>>>>>> --- a/hw/scsi/megasas.c
>>>>>>>> +++ b/hw/scsi/megasas.c
>>>>>>>> @@ -2084,7 +2084,8 @@ static const VMStateDescription vmstate_megasas 
>>>>>>>> = {
>>>>>>>>       .minimum_version_id = 0,
>>>>>>>>       .minimum_version_id_old = 0,
>>>>>>>>       .fields      = (VMStateField[]) {
>>>>>>>> -        VMSTATE_PCI_DEVICE(parent_obj, MegasasState),
>>>>>>>> +        VMSTATE_PCIE_DEVICE(parent_obj, MegasasState),
>>>>>>>> +        VMSTATE_MSIX(parent_obj, MegasasState),
>>>>>>>
>>>>>>> This requires a version change for vmstate, no?
>>>>>>
>>>>>> The PCI -> PCIE change yes. mst might have objections for bumping an x86
>>>>>> PCI device?
>>>>>
>>>>> Yes.
>>>>> It should be possible to make this conditional on having a pcie
>>>>> capability, and disable pcie capability for old pc versions.
>>>>
>>>> I did have a patch merging their vmstate_ structs based on some test in
>>>> the series I ping'ed, unfortunately the difference was mostly config
>>>> space size, so not immediately obvious how to set via compat_props, but
>>>> likely solvable somehow.
>>>
>>> Check pci_is_express ?
>>>
>>>>>> The MSIX addition should be safe AFAICT since old versions would not
>>>>>> enable MSI-X.
>>>>>
>>>>> Yes but I don't see a code like this - where's code in PC
>>>>> disabling msix for old versions?
>>>>
>>>> The default value for use_msix (use-msix?) in v2 is already false, so no
>>>> need to set it to false again in compat_props?
>>>>
>>>> Andreas
>>>
>>> Ah, I didn't notice that. Sure, if it's off by default there's
>>> no need for compat code.
>>>
>> And the net result is ... what?
>> Do I need to change the code?
> 
> Yes, NAK for this patch as is.
> 
> Why are you changing VMSTATE_PCI_DEVICE() to VMSTATE_PCIE_DEVICE()? Was
> it always a PCIe device and you're fixing that now? Then put it into its
> own patch with proper explanation, setting pdc->is_express = 1 *and*
> assure there via some compatibility property (?) that migration from
> 2.0.0-rc3 to the patched version succeeds (which would probably still
> break backwards migration that mst was interested in though).
> 
The thing was always PCIe; it's just that at the time I've
originally implemented it MSI-X support was broken, and PCIe even
more so. So I figured to take the easy way out and implement it as a
normal PCI device.

I'm happy to continue with having the original implementation at
PCI, and only moving to PCIe with the gen2 emulation.

Would that be okay?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                   zSeries & Storage
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