Re: Dropped/disabled NVME support in qemu

[Guenter Roeck]

Hi Klaus,

On 12/21/20 7:17 AM, Klaus Jensen wrote:
> On Dec 21 15:11, Philippe Mathieu-Daudé wrote:
>> Cc'ing NVMe emulation maintainers.
>>
>> On 12/21/20 6:12 AM, Guenter Roeck wrote:
>>> Hi all,
>>>
>>> since qemu v5.1, nvme support has been dropped from several architectures.
>>> Well, it was not exactly dropped, but disabled.
>>>
>>> On those architectures, trying to boot from an nvme drive now results
>>> in the following or a similar error message.
>>>
>>> qemu-system-alpha: -device nvme,serial=foo,drive=d0: MSI-X is not supported 
>>> by interrupt controller
>>>
>>> This is the result of the following two commits.
>>>
>>> fbf2e5375e ("hw/block/nvme: Verify msix_vector_use() returned value")
>>> 1c0c2163aa ("hw/block/nvme: verify msix_init_exclusive_bar() return value")
>>>
>>> Affected architectures are alpha, parisc, ppc, sh, and sparc, and every 
>>> other
>>> architecture/platform where the interrupt controller does not support MSI-X.
>>> After reverting above patches, I can boot from nvme again.
>>>
>>> This does not really matter for me - I run my own versions of qemu anyway,
>>> and don't mind carrying reverts if I have to. However, for my education,
>>> I would like to understand why nvme support was disabled, especially since
>>> it seemed to work for me just fine for years. Can someone please explain ?
>>>
>>> Thanks,
>>> Guenter
>>>
>>
> 
> Hi Guenter,
> 
> Thanks for reporting this. My apologies - this is an unintended
> regression. I'll get a revert staged.
> 
> I'll of course also look into why this was not picked up doing testing.
> There is an nvme QTest that should have picked this up, but it obviously
> was not run for these architectures.
> 

Ah, that explains a lot. Just a thought: instead of reverting the patches,
it might possibly make sense to handle lack of MSI-X support explicitly.

Thanks,
Guenter

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