Messages in this thread | | | Date | Tue, 16 Nov 2021 08:33:42 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH 16/39] irqdomain: Make normal and nomap irqdomains exclusive |
| |
On Mon, 15 Nov 2021 19:05:17 +0000, Cédric Le Goater <clg@kaod.org> wrote: > > Hello Mark,
s/k/c/
> > On 5/20/21 18:37, Marc Zyngier wrote: > > Direct mappings are completely exclusive of normal mappings, meaning > > that we can refactor the code slightly so that we can get rid of > > the revmap_direct_max_irq field and use the revmap_size field > > instead, reducing the size of the irqdomain structure. > > > > Signed-off-by: Marc Zyngier <maz@kernel.org> > > > This patch is breaking the POWER9/POWER10 XIVE driver (these are not > old PPC systems :) on machines sharing the same LSI HW IRQ. For instance, > a linux KVM guest with a virtio-rng and a virtio-balloon device. In that > case, Linux creates two distinct IRQ mappings which can lead to some > unexpected behavior.
Either the irq domain translates, or it doesn't. If the driver creates a nomap domain, and yet expects some sort of translation to happen, then the driver is fundamentally broken. And even without that: how do you end-up with a single HW interrupt having two mappings?
> A fix to go forward would be to change the XIVE IRQ domain to use a > 'Tree' domain for reverse mapping and not the 'No Map' domain mapping. > I will keep you updated for XIVE.
I bet there is a bit more to it. From what you are saying above, something rather ungodly is happening in the XIVE code.
M.
-- Without deviation from the norm, progress is not possible.
| |