On 06.11.2024 13:26, Mykyta Poturai wrote:
> On 06.11.2024 10:07, Roger Pau Monné wrote:>
>> Wait - how can msi->vectors ever be 0? AFAICT there's no way in the
>> MSI logic to configure 0 vectors, there will always be at least 1 vector
>> enabled.
>>
>> Maybe what you want, if this fix is for compliance reasons, is an
>> assert unreachable that msi->vectors > 0?
>
> I did some investigation and figured out that the value of 0 is being
> set by guest writing to msi_control_reg. As far as I understand, the
> control_write() function only checks that vectors are not greater than
> the maximum allowed value, but does not check for 0.
How that? How could it even check for 0, when 0 isn't possible? Quoting
the code there:
unsigned int vectors = min_t(uint8_t,
1u << MASK_EXTR(val, PCI_MSI_FLAGS_QSIZE),
pdev->msi_maxvec);
"val" in the guest written value. As that's used as a shift count, how
could 0 result there? The only way I can see 0 ending up in vectors is
when pdev->msi_maxvec was still zero. Yet that's then a bug in device
initialization.
Jan
