Re: [PATCH v2] KVM: Implement support for the RH bit

Jan Kiszka
2011-09-02T11:37:02Z

On 2011-09-02 13:27, Jan Kiszka wrote:
> On 2011-09-02 09:48, Sasha Levin wrote:
>> The RH bit exists in the message address register (lower 32 bits of
>> the address).
>>
>> The bit indicates whether the message should go to the processor which was
>> indicated in the destination ID bits, or whether it should go to the
>> processor running at the lowest priority.
>>
>> Cc: Avi Kivity <avi@redhat.com>
>> Cc: Marcelo Tosatti <mtosatti@redhat.com>
>> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
>> ---
>> virt/kvm/irq_comm.c | 17 ++++++++++++++++-
>> 1 files changed, 16 insertions(+), 1 deletions(-)
>>
>> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
>> index 9f614b4..0ba3a3d 100644
>> --- a/virt/kvm/irq_comm.c
>> +++ b/virt/kvm/irq_comm.c
>> @@ -134,7 +134,22 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
>> irq.level = 1;
>> irq.shorthand = 0;
>>
>> - /* TODO Deal with RH bit of MSI message address */
>> + /*
>> + * If the RH bit is set, we'll deliver to the processor running
>> + * at the lowest priority.
>> + */
>> + if (e->msi.address_lo & MSI_ADDR_REDIRECTION_LOWPRI) {
>> + irq.delivery_mode = MSI_DATA_DELIVERY_LOWPRI;
>> + } else {
>> + /*
>> + * If the RH bit is not set, we'll deliver to the specific
>> + * processor mentioned in destination ID, and ignore the DM
>> + * bit.
>> + */
>> + irq.dest_mode = MSI_ADDR_DEST_MODE_PHYSICAL;
>> + irq.delivery_mode = MSI_DATA_DELIVERY_FIXED;
>> + }
>> +
>> return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
>> }
>>
>
> Do you happen have a kvm unit test for this? Or how did you validate the
> change? It doesn't look incorrect to me, I'd just like to check it QEMU
> as well which apparently already has the logic above but also some
> contradictory comment.

Err, no, QEMU does not have this logic, it also ignores RH.

But the above bits make "irq.delivery_mode = e->msi.data & 0x700"
pointless. And that strongly suggests something is still wrong.