Re: [RFC PATCH v5 1/1] KVM: s390: Clarify SIGP orders versus STOP/RESTART

Christian Borntraeger
2021-12-15T13:57:41Z

Am 15.12.21 um 14:24 schrieb David Hildenbrand:
> On 13.12.21 22:05, Eric Farman wrote:
>> With KVM_CAP_S390_USER_SIGP, there are only five Signal Processor
>> orders (CONDITIONAL EMERGENCY SIGNAL, EMERGENCY SIGNAL, EXTERNAL CALL,
>> SENSE, and SENSE RUNNING STATUS) which are intended for frequent use
>> and thus are processed in-kernel. The remainder are sent to userspace
>> with the KVM_CAP_S390_USER_SIGP capability. Of those, three orders
>> (RESTART, STOP, and STOP AND STORE STATUS) have the potential to
>> inject work back into the kernel, and thus are asynchronous.
>>
>> Let's look for those pending IRQs when processing one of the in-kernel
>> SIGP orders, and return BUSY (CC2) if one is in process. This is in
>> agreement with the Principles of Operation, which states that only one
>> order can be "active" on a CPU at a time.
>>
>> Suggested-by: David Hildenbrand <david@redhat.com>
>> Signed-off-by: Eric Farman <farman@linux.ibm.com>
>> ---
>
> In general, LGTM. As raised, with SIGP RESTART there are other cases we
> could fix in the kernel, but they are of very low priority IMHO.

Does that qualify as an RB, assuming that we can fix the other cases later on?