On Fri, Feb 27, 2026 at 01:25:03PM +0800, Vivian Wang wrote:

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

quoted

On 29/01/2026 3:56, Vivian Wang wrote:

quoted

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.

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

We needed testing on powerpc and sparc, which has now been done,
thanks to Han Gao (SPARC Enterprise T5220), Nathaniel Roach (SPARC
T5-2), and Venkat Rao Bagalkote (IBM Power System LPAR (pseries)).

It would be ideal to have acks from the powerpc and sparc maintainers,
so I just solicited those.

Thomas merged 386ced19e9a3 ("PCI/MSI: Convert the boolean no_64bit_msi
flag to a DMA address mask"), and could merge the fixes.  Otherwise I
can merge via PCI.

Bjorn