Re: MSIs not freed in GICv3 ITS driver

[Marc Zyngier <maz@kernel.org>]

On Wed, 01 Apr 2026 08:59:02 +0100,
Manivannan Sadhasivam <mani@kernel.org> wrote:
> 
> On Mon, Mar 30, 2026 at 09:17:10AM +0100, Marc Zyngier wrote:
> > On Tue, 03 Mar 2026 09:26:32 +0000,
> > Manivannan Sadhasivam <mani@kernel.org> wrote:
> > > 
> > > The above issue should be applicable to other MSI controller drivers as well,
> > > not just DWC.
> > 
> > The core issue is not with the irqchips, but with the MSI subsystem.
> > 
> > Multi-MSI devices should always result in a strict power-of-2
> > allocation, because that's all the HW supports. Yet, we let drivers
> > request a stupid number of interrupts.
> > 
> > I can see two outcomes: either we force the allocation to the next 2^
> > value, or we return an error to the caller. The first one costs memory
> > (extra irq descriptors), the latter forces people to fix their crap.
> > 
> > I'm tempted to propose the latter.
> > 
> 
> That might cause a lot of regressions I believe. IMO, safe bet would be to
> handle the power of 2 allocations inside the irqchip drivers.

What part of "this is a violation of the PCI spec" did you miss? I
didn't realise we were in the business of adding crap just because
endpoint drivers are broken.

In any case, I'm not touching the ITS driver.

	M.

-- 
Without deviation from the norm, progress is not possible.