| Message ID | 87fwe68lt0.fsf@rustcorp.com.au |
|---|---|
| State | New |
| Headers | show |
On Sun, Feb 19, 2012 at 6:07 PM, Rusty Russell <rusty@rustcorp.com.au> wrote: > We currently assume that the number of interrupts (ITLinesNumber in > the architecture reference manual) is divisible by 32, since we > present it to the guest when it reads GICD_TYPER (in gic_dist_readb()) > as (N - 32) / 1. > > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> > > diff --git a/hw/arm_gic.c b/hw/arm_gic.c > index fa6a60a..6446800 100644 > --- a/hw/arm_gic.c > +++ b/hw/arm_gic.c > @@ -818,6 +818,15 @@ static void gic_init(gic_state *s, int num_irq) > hw_error("requested %u interrupt lines exceeds GIC maximum %d\n", > num_irq, GIC_MAXIRQ); > } > + /* ITLinesNumber is represented as (N - 32) / 1 (see > + * gic_dist_readb) so this is an implementation imposed > + * restriction, not an architectural one: > + */ What is this division by 1? Isn't (N - 32) / 1 == (N - 32) and how does that explain the division. Was it (N / 32) - 1? Or is this a cast? Or am I missing something completely? > + if (s->num_irq < 32 || (s->num_irq % 32)) { > + hw_error("%d interrupt lines unsupported: not divisible by 32\n", > + num_irq); > + } > + > qdev_init_gpio_in(&s->busdev.qdev, gic_set_irq, s->num_irq - GIC_INTERNAL); > for (i = 0; i < NUM_CPU(s); i++) { > sysbus_init_irq(&s->busdev, &s->parent_irq[i]); > _______________________________________________ > Android-virt mailing list > Android-virt@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/android-virt
On Sun, 19 Feb 2012 18:40:08 -0500, Christoffer Dall <c.dall@virtualopensystems.com> wrote: > On Sun, Feb 19, 2012 at 6:07 PM, Rusty Russell <rusty@rustcorp.com.au> wrote: > > We currently assume that the number of interrupts (ITLinesNumber in > > the architecture reference manual) is divisible by 32, since we > > present it to the guest when it reads GICD_TYPER (in gic_dist_readb()) > > as (N - 32) / 1. > > > > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> > > > > diff --git a/hw/arm_gic.c b/hw/arm_gic.c > > index fa6a60a..6446800 100644 > > --- a/hw/arm_gic.c > > +++ b/hw/arm_gic.c > > @@ -818,6 +818,15 @@ static void gic_init(gic_state *s, int num_irq) > > hw_error("requested %u interrupt lines exceeds GIC maximum %d\n", > > num_irq, GIC_MAXIRQ); > > } > > + /* ITLinesNumber is represented as (N - 32) / 1 (see > > + * gic_dist_readb) so this is an implementation imposed > > + * restriction, not an architectural one: > > + */ > > What is this division by 1? Isn't (N - 32) / 1 == (N - 32) and how > does that explain the division. Was it (N / 32) - 1? Or is this a > cast? Or am I missing something completely? That's hilarious; we were concentrating so hard on the wording of the comment, we didn't notice that I completely screwed the content :) It is, of course, (N / 32) - 1: static uint32_t gic_dist_readb(void *opaque, target_phys_addr_t offset) { ... if (offset == 4) return ((GIC_NIRQ / 32) - 1) | ((NUM_CPU(s) - 1) << 5); I'll fix it, thanks! Rusty.
diff --git a/hw/arm_gic.c b/hw/arm_gic.c index fa6a60a..6446800 100644 --- a/hw/arm_gic.c +++ b/hw/arm_gic.c @@ -818,6 +818,15 @@ static void gic_init(gic_state *s, int num_irq) hw_error("requested %u interrupt lines exceeds GIC maximum %d\n", num_irq, GIC_MAXIRQ); } + /* ITLinesNumber is represented as (N - 32) / 1 (see + * gic_dist_readb) so this is an implementation imposed + * restriction, not an architectural one: + */ + if (s->num_irq < 32 || (s->num_irq % 32)) { + hw_error("%d interrupt lines unsupported: not divisible by 32\n", + num_irq); + } + qdev_init_gpio_in(&s->busdev.qdev, gic_set_irq, s->num_irq - GIC_INTERNAL); for (i = 0; i < NUM_CPU(s); i++) { sysbus_init_irq(&s->busdev, &s->parent_irq[i]);
We currently assume that the number of interrupts (ITLinesNumber in the architecture reference manual) is divisible by 32, since we present it to the guest when it reads GICD_TYPER (in gic_dist_readb()) as (N - 32) / 1. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>