Re: [PATCH] powerpc/xive: Change IRQ domain to a tree domain

[Greg Kurz <groug@kaod.org>]

On Tue, 16 Nov 2021 15:49:13 +0100
Cédric Le Goater <clg@kaod.org> wrote:

> On 11/16/21 15:23, Greg Kurz wrote:
> > On Tue, 16 Nov 2021 14:40:22 +0100
> > Cédric Le Goater <clg@kaod.org> wrote:
> > 
> >> Commit 4f86a06e2d6e ("irqdomain: Make normal and nomap irqdomains
> >> exclusive") introduced an IRQ_DOMAIN_FLAG_NO_MAP flag to isolate the
> >> 'nomap' domains still in use under the powerpc arch. With this new
> >> flag, the revmap_tree of the IRQ domain is not used anymore. This
> >> change broke the support of shared LSIs [1] in the XIVE driver because
> >> it was relying on a lookup in the revmap_tree to query previously
> >> mapped interrupts. Linux now creates two distinct IRQ mappings on the
> >> same HW IRQ which can lead to unexpected behavior in the drivers.
> >>
> >> The XIVE IRQ domain is not a direct mapping domain and its HW IRQ
> >> interrupt number space is rather large : 1M/socket on POWER9 and
> >> POWER10, change the XIVE driver to use a 'tree' domain type instead.
> >>
> >> [1] For instance, a linux KVM guest with virtio-rng and virtio-balloon
> >>      devices.
> >>
> >> Cc: Marc Zyngier <maz@kernel.org>
> >> Cc: stable@vger.kernel.org # v5.14+
> >> Fixes: 4f86a06e2d6e ("irqdomain: Make normal and nomap irqdomains exclusive")
> >> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> >> ---
> >>
> > 
> > Tested-by: Greg Kurz <groug@kaod.org>
> > 
> > with a KVM guest + virtio-rng + virtio-balloon on a POWER9 host.
> 
> Did you test on a 5.14 backport or mainline ?
> 

I've tested on a 5.14 backport only.

> I am asking because a large change adding support for MSI domains
> to XIVE was merged in 5.15.
> 
> Thanks,
> 
> C.
> 
> 
> > 
> >>   Marc,
> >>
> >>   The Fixes tag is there because the patch in question revealed that
> >>   something was broken in XIVE. genirq is not in cause. However, I
> >>   don't know for PS3 and Cell. May be less critical for now.
> >>   
> >>   arch/powerpc/sysdev/xive/common.c | 3 +--
> >>   arch/powerpc/sysdev/xive/Kconfig  | 1 -
> >>   2 files changed, 1 insertion(+), 3 deletions(-)
> >>
> >> diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
> >> index fed6fd16c8f4..9d0f0fe25598 100644
> >> --- a/arch/powerpc/sysdev/xive/common.c
> >> +++ b/arch/powerpc/sysdev/xive/common.c
> >> @@ -1536,8 +1536,7 @@ static const struct irq_domain_ops xive_irq_domain_ops = {
> >>   
> >>   static void __init xive_init_host(struct device_node *np)
> >>   {
> >> -	xive_irq_domain = irq_domain_add_nomap(np, XIVE_MAX_IRQ,
> >> -					       &xive_irq_domain_ops, NULL);
> >> +	xive_irq_domain = irq_domain_add_tree(np, &xive_irq_domain_ops, NULL);
> >>   	if (WARN_ON(xive_irq_domain == NULL))
> >>   		return;
> >>   	irq_set_default_host(xive_irq_domain);
> >> diff --git a/arch/powerpc/sysdev/xive/Kconfig b/arch/powerpc/sysdev/xive/Kconfig
> >> index 97796c6b63f0..785c292d104b 100644
> >> --- a/arch/powerpc/sysdev/xive/Kconfig
> >> +++ b/arch/powerpc/sysdev/xive/Kconfig
> >> @@ -3,7 +3,6 @@ config PPC_XIVE
> >>   	bool
> >>   	select PPC_SMP_MUXED_IPI
> >>   	select HARDIRQS_SW_RESEND
> >> -	select IRQ_DOMAIN_NOMAP
> >>   
> >>   config PPC_XIVE_NATIVE
> >>   	bool
> > 
>