Re: [PATCH 20/35] irqchip/gic-v4.1: Allow direct invalidation of VLPIs

[Zenghui Yu]

On 2019/9/30 17:20, Marc Zyngier wrote:
> On 2019-09-28 03:02, Zenghui Yu wrote:
> > On 2019/9/24 2:25, Marc Zyngier wrote:
> > > Just like for INVALL, GICv4.1 has grown a VPE-aware INVLPI register.
> > > Let's plumb it in and make use of the DirectLPI code in that case.
> > > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > > ---
> > > Â drivers/irqchip/irq-gic-v3-its.cÂÂ | 19 +++++++++++++++++--
> > > Â include/linux/irqchip/arm-gic-v3.h |Â 1 +
> > > Â 2 files changed, 18 insertions(+), 2 deletions(-)
> > > diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> > > b/drivers/irqchip/irq-gic-v3-its.c
> > > index b791c9beddf2..34595a7fcccb 100644
> > > --- a/drivers/irqchip/irq-gic-v3-its.c
> > > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > > @@ -1200,13 +1200,27 @@ static void wait_for_syncr(void __iomem *rdbase)
> > > Â static void direct_lpi_inv(struct irq_data *d)
> > > Â {
> > > +ÂÂÂ struct its_vlpi_map *map = get_vlpi_map(d);
> > > ÂÂÂÂÂ struct its_collection *col;
> > > ÂÂÂÂÂ void __iomem *rdbase;
> > > +ÂÂÂ u64 val;
> > > +
> > > +ÂÂÂ if (map) {
> > > +ÂÂÂÂÂÂÂ struct its_device *its_dev = irq_data_get_irq_chip_data(d);
> > > +
> > > +ÂÂÂÂÂÂÂ WARN_ON(!is_v4_1(its_dev->its));
> > > +
> > > + val = GICR_INVLPIR_V;
> > > +ÂÂÂÂÂÂÂ val |= FIELD_PREP(GICR_INVLPIR_VPEID, map->vpe->vpe_id);
> > > +ÂÂÂÂÂÂÂ val |= FIELD_PREP(GICR_INVLPIR_INTID, map->vintid);
> > > +ÂÂÂ } else {
> > > +ÂÂÂÂÂÂÂ val = d->hwirq;
> > > +ÂÂÂ }
> > >
> > > ÂÂÂÂÂ /* Target the redistributor this LPI is currently routed to */
> > > ÂÂÂÂÂ col = irq_to_col(d);
> >
> > I think irq_to_col() may not work when GICv4.1 VLPIs are involved in.
> >
> > irq_to_col() gives us col_map[event] as the target redistributor,
> > but the correct one for VLPIs should be vlpi_maps[event]->vpe->col_idx.
> > These two are not always pointing to the same physical RD.
> > For example, if guest issues a MOVI against a VLPI, we will update the
> > corresponding vlpi_map->vpe and issue a VMOVI on ITS... but leave the
> > col_map[event] unchanged.
> >
> > col_map[event] usually describes the physical LPI's CPU affinity, but
> > when this physical LPI serves as something which the VLPI is backed by,
> > we take really little care of it. Did I miss something here?
>
> You didn't miss anything, and this is indeed another pretty bad bug.
> The collection mapping is completely unused when the LPI becomes a
> VLPI, and it is only the vpe->col_id that matters (which gets updated
> on VMOVP).
>
> This shows that irq_to_col() is the wrong abstraction, and what we're
> interested is something that is more like 'irq to cpuid', allowing us
> to directly point to the right distributor.
>
> Please see the patch I just pushed[1], which does that.
>
> Thanks,
>
>  ÂÂÂÂÂÂÂ M.
>
> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/gic-v4.1-devel&id=aff363113eb26b6840136b69c2c7db2ea691db20 

Yes, I think this makes sense.


Thanks,
zenghui