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

[Jan Kiszka <jan.kiszka@siemens.com>]

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.

Jan

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