Re: [PATCH] irqchip/gic-v3-its: Don't confuse get_vlpi_map() by writing DB config

[Marc Zyngier]

On 2020-01-22 11:29, Zenghui Yu wrote:
> Hi Marc,
>
> On 2020/1/22 18:44, Marc Zyngier wrote:
> > Hi Zenghui,
> >
> > Thanks for this.
> >
> > On 2020-01-22 08:56, Zenghui Yu wrote:
> > > When we're writing config for the doorbell interrupt, get_vlpi_map() 
> > > will
> > > get confused by doorbell's d->parent_data hack and find the wrong 
> > > its_dev
> > > as chip data and the wrong event.
> > >
> > > Fix this issue by making sure no doorbells will be involved before 
> > > invoking
> > > get_vlpi_map(), which restore some of the logic in 
> > > lpi_write_config().
> > >
> > > Fixes: c1d4d5cd203c ("irqchip/gic-v3-its: Add its_vlpi_map helpers")
> > > Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
> > > ---
> > >
> > > This is based on mainline and can't be directly applied to the 
> > > current
> > > irqchip-next.
> > >
> > > Âdrivers/irqchip/irq-gic-v3-its.c | 5 +++--
> > > Â1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> > > b/drivers/irqchip/irq-gic-v3-its.c
> > > index e05673bcd52b..cc8a4fcbd6d6 100644
> > > --- a/drivers/irqchip/irq-gic-v3-its.c
> > > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > > @@ -1181,12 +1181,13 @@ static struct its_vlpi_map
> > > *get_vlpi_map(struct irq_data *d)
> > >
> > > Âstatic void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
> > > Â{
> > > -ÂÂÂ struct its_vlpi_map *map = get_vlpi_map(d);
> > > ÂÂÂÂ irq_hw_number_t hwirq;
> > > ÂÂÂÂ void *va;
> > > ÂÂÂÂ u8 *cfg;
> > >
> > > -ÂÂÂ if (map) {
> > > +ÂÂÂ if (irqd_is_forwarded_to_vcpu(d)) {
> > > +ÂÂÂÂÂÂÂ struct its_vlpi_map *map = get_vlpi_map(d);
> > > +
> > > ÂÂÂÂÂÂÂÂ va = page_address(map->vm->vprop_page);
> > > ÂÂÂÂÂÂÂÂ hwirq = map->vintid;
> >
> > Shouldn't we fix get_vlpi_map() instead? Something like (untested):
> >
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> > b/drivers/irqchip/irq-gic-v3-its.c
> > index e05673bcd52b..b704214390c0 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -1170,13 +1170,14 @@ static void its_send_vclear(struct its_device 
> > *dev, u32 event_id)
> >  Â */
> >  Âstatic struct its_vlpi_map *get_vlpi_map(struct irq_data *d)
> >  Â{
> > -ÂÂÂ struct its_device *its_dev = irq_data_get_irq_chip_data(d);
> > -ÂÂÂ u32 event = its_get_event_id(d);
> > +ÂÂÂ if (irqd_is_forwarded_to_vcpu(d)) {
> > +ÂÂÂÂÂÂÂ struct its_device *its_dev = irq_data_get_irq_chip_data(d);
> > +ÂÂÂÂÂÂÂ u32 event = its_get_event_id(d);
> >
> > -ÂÂÂ if (!irqd_is_forwarded_to_vcpu(d))
> > -ÂÂÂÂÂÂÂ return NULL;
> > +ÂÂÂÂÂÂÂ return dev_event_to_vlpi_map(its_dev, event);
> > +ÂÂÂ }
> >
> > -ÂÂÂ return dev_event_to_vlpi_map(its_dev, event);
> > +ÂÂÂ return NULL;
> >  Â}
> >
> >  Âstatic void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
> >
> >
> > Or am I missing the actual problem?
>
> No. I also thought about fixing the issue by this way and I'm OK with
> both approaches.

OK, thanks. I've added this to irqchip-next[1], and rebased the v4.1
series on top of it. That way, the fix will trickle down to stable
without conflicts.

I've also given it a go on D05 with GICv4 enabled, and nothing caught 
fire.

        M.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/irqchip-next&id=093bf439fee0d40ade7e309c1288b409cdc3b38f
--
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