On Tue, 16 Nov 2021 14:40:22 +0100
Cédric Le Goater <clg@xxxxxxxx> 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@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v5.14+
> Fixes: 4f86a06e2d6e ("irqdomain: Make normal and nomap irqdomains exclusive")
> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
> ---
>
Tested-by: Greg Kurz <groug@xxxxxxxx>
with a KVM guest + virtio-rng + virtio-balloon on a POWER9 host.
> 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
