Re: [PATCH v4 1/4] PCI/MSI: Conservatively generalize no_64bit_msi into msi_addr_mask

Vivian Wang
2026-02-27T05:25:45Z

On 2/27/26 02:25, Mark Bloch wrote:

> On 29/01/2026 3:56, Vivian Wang wrote:
>> Some PCI devices have PCI_MSI_FLAGS_64BIT in the MSI capability, but
>> implement less than 64 address bits. This breaks on platforms where such
>> a device is assigned an MSI address higher than what's reachable.
>>
>> Currently, the no_64bit_msi bit is set for these devices, meaning that
>> only 32-bit MSI addresses are allowed for them. However, on some
>> platforms the MSI doorbell address is above the 32-bit limit but within
>> the addressable range of the device.
>>
>> As a first step to enabling MSI on those combinations of devices and
>> platforms, conservatively generalize the single-bit flag no_64bit_msi
>> into msi_addr_mask. (The name msi_addr_mask is chosen to avoid confusion
>> with msi_mask.)
>>
>> The translation is essentially:
>>
>> - no_64bit_msi = 1 -> msi_addr_mask = DMA_BIT_MASK(32)
>> - no_64bit_msi = 0 -> msi_addr_mask = DMA_BIT_MASK(64)
>> - if (no_64bit_msi) -> if (msi_addr_mask < DMA_BIT_MASK(64))
>>
> Hey Vivian,
>
> We are seeing issues while reloading mlx5 on a PPC64 platform.

Mea culpa. There's a fix on the list [1] since last Friday. I'm not sure
why it hasn't moved yet, but please take a look.

Vivian "dramforever" Wang

[1]: https://lore.kernel.org/all/20260220070239.1693303-1-nilay@linux.ibm.com/