Re: [Qemu-devel] [PATCH v5 2/2] arm_gicv3_kvm: kvm_dist_get/put: skip the registers banked by GICR

[Shannon Zhao <shannon.zhaosl@gmail.com>]

2018-05-31 21:50 GMT+08:00 Peter Maydell <peter.maydell@linaro.org>:

> On 31 May 2018 at 04:15, Shannon Zhao <zhaoshenglong@huawei.com> wrote:
> > While we skip the GIC_INTERNAL irqs, we don't change the register offset
> > accordingly. This will overlap the GICR registers value and leave the
> > last GIC_INTERNAL irq's registers out of update.
> >
> > Fix this by skipping the registers banked by GICR.
> >
> > Also for migration compatibility if the migration source (old version
> > qemu) doesn't send gicd_no_migration_shift_bug = 1 to destination, then
> > we shift the data of PPI to get the right data for SPI.
> >
> > Fixes: 367b9f527becdd20ddf116e17a3c0c2bbc486920
> > Cc: qemu-stable@nongnu.org
> > Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
>
> > +    /*
> > +     * While this new version QEMU doesn't have this kind of bug as we
> fix it,
> > +     * so it's need to set the flag to true to indicate that and it's
> neccessary
> > +     * for next migration to work from this new version QEMU.
> > +     */
> > +    cs->gicd_no_migration_shift_bug = true;
>
> Nice catch; I would have forgotten that we needed to do this...
>
>
> >
> > +    /* For the KVM GICv3, affinity routing is always enabled, and the
> > +     * GICD_IGROUPR0/GICD_IGRPMODR0/GICD_ISENABLER0/GICD_ISPENDR0/
> > +     * GICD_ISACTIVER0 registers are always RAZ/WI. The corresponding
> > +     * functionality is replaced by the GICR registers. It doesn't need
> to sync
> > +     * them. So it should increase the offset to skip GIC_INTERNAL irqs.
> > +     * This matches the for_each_dist_irq_reg() macro which also skips
> the
> > +     * first GIC_INTERNAL irqs.
> > +     */
> > +    offset += (GIC_INTERNAL * 1) / 8;
> > +    if (clroffset != 0) {
> > +        clroffset += (1 * sizeof(uint32_t));
> > +    }
> > +
>
> Shouldn't we be adding the same thing to clroffset that we add to offset ?
>
> Yeah, right. It should like this

  clroffset += (GIC_INTERNAL * 1) / 8;

I don't remember why I didn't write this way. Anyway, Could you please fix
this when you apply this patch or I send a new version?

Thanks,
--
Shannon