On Fri, 06 Jun 2014 15:15:54 +0200
Alexander Graf <agraf@xxxxxxx> wrote:
>
> On 06.06.14 15:12, Cornelia Huck wrote:
> > On Fri, 6 Jun 2014 14:46:05 +0200
> > Alexander Graf <agraf@xxxxxxx> wrote:
> >
> >> KVM tells us the number of GSIs it can handle inside the kernel. That value is
> >> basically KVM_MAX_IRQ_ROUTES. However when we try to set the GSI mapping table,
> >> it checks for
> >>
> >> r = -EINVAL;
> >> if (routing.nr >= KVM_MAX_IRQ_ROUTES)
> >> goto out;
> >>
> >> erroring out even when we're only using all of the GSIs. To make sure we never
> >> hit that limit, let's reduce the number of GSIs we get from KVM by one.
> >>
> >> Signed-off-by: Alexander Graf <agraf@xxxxxxx>
> >> ---
> >> kvm-all.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/kvm-all.c b/kvm-all.c
> >> index 4e19eff..56a251b 100644
> >> --- a/kvm-all.c
> >> +++ b/kvm-all.c
> >> @@ -938,7 +938,7 @@ void kvm_init_irq_routing(KVMState *s)
> >> {
> >> int gsi_count, i;
> >>
> >> - gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING);
> >> + gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1;
> >> if (gsi_count > 0) {
> >> unsigned int gsi_bits, i;
> >>
> > But gsi_count is already marked as used further down in this function,
> > isn't it? Confused.
>
> gsi_bits = ALIGN(gsi_count, 32);
> [...]
> for (i = gsi_count; i < gsi_bits; i++) {
> set_gsi(s, i);
> }
>
> So if you take gsi_count = 1024, what happens?
>
> gsi_count = 1024;
> gsi_bits = 1024;
> for (i = 1024; i < 1024; i++) {
> set_gsi(s, i);
> }
>
> At least in my world of C that loop never runs, no?
>
But then kvm_irqchip_get_virq() should never return 1024, shouldn't it?
And:
void kvm_irqchip_add_irq_route(KVMState *s, int irq, int irqchip, int pin)
{
[...]
assert(pin < s->gsi_count);
would trigger too early with your change, wouldn't it?
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