On 03/10/2015 08:47 AM, Radim Krčmář wrote:
...
>> + /*
>> + * Set dest_mode to logical just in case both the RH and DM
>> + * bits are set, otherwise default to physical.
>> + */
>> + phys = ((e->msi.address_lo & (MSI_ADDR_REDIRECTION_LOWPRI |
>> + MSI_ADDR_DEST_MODE_LOGICAL)) !=
>> + (MSI_ADDR_REDIRECTION_LOWPRI |
>> + MSI_ADDR_DEST_MODE_LOGICAL));
>> + irq->dest_mode = phys ? 0 : (MSI_ADDR_DEST_MODE_LOGICAL);
>
> (Should be APIC_DEST_LOGICAL. All works because it is a boolean and we
> only checked for APIC_DEST_PHYSICAL, which is 0.)
>
Thank you, that should be as follows:
irq->dest_mode = phys ? (APIC_DEST_PHYSICAL) : (APIC_DEST_LOGICAL);
?
>> irq->trig_mode = (1 << MSI_DATA_TRIGGER_SHIFT) & e->msi.data;
>> irq->delivery_mode = e->msi.data & 0x700;
>> irq->level = 1;
>> irq->shorthand = 0;
>> - /* TODO Deal with RH bit of MSI message address */
>
> RH bit still isn't deal with -- we do not use lowest-priority-like
> delivery in logical destination mode ...
Just want to make sure I understand this comment-
Isn't low-pri delivery mode used in kvm_irq_delivery_to_apic_fast
when irq->dest_mode > APIC_DEST_PHYSICAL (ie, logical)? (See below.)
Do you mean that this patch will interfere with this? As long as
irq->dest_mode is still APIC_DEST_LOGICAL this shouldn't change.
bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq, int *r, unsigned long *dest_map)
{
.....
if (irq->dest_mode == APIC_DEST_PHYSICAL) {
if (irq->dest_id >= ARRAY_SIZE(map->phys_map))
goto out;
dst = &map->phys_map[irq->dest_id];
} else {
u32 mda = irq->dest_id << (32 - map->ldr_bits);
u16 cid = apic_cluster_id(map, mda);
if (cid >= ARRAY_SIZE(map->logical_map))
goto out;
dst = map->logical_map[cid];
bitmap = apic_logical_id(map, mda);
if (irq->delivery_mode == APIC_DM_LOWEST) {
int l = -1;
for_each_set_bit(i, &bitmap, 16) {
if (!dst[i])
continue;
if (l < 0)
l = i;
else if (kvm_apic_compare_prio(dst[i]->vcpu,
dst[l]->vcpu) < 0)
l = i;
}
bitmap = (l >= 0) ? 1 << l : 0;
}
}
.....
}
> How does DM=1/RH=1 work on real hardware?
> (There seem to be interesting corner cases with irq->delivery_mode like
> APIC_DM_NMI.)
>
The IA32 manual says that if DM=1/RH=1, we operate in logical destination mode
similarly to other IPIs. I don't believe this patch introduces any invalid
settings listed in section 10-21, Vol. 3, so this shouldn't create any
weirdness.
Thanks
-James
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