On 09/02/2021 17.14, Janosch Frank wrote:
On 2/9/21 5:08 PM, Claudio Imbrenda wrote:
On Tue, 9 Feb 2021 09:15:54 -0500
Janosch Frank <frankja@xxxxxxxxxxxxx> wrote:
KVM and QEMU handle a SIGP stop and store status in two steps:
1) Stop the CPU by injecting a stop request
2) Store when the CPU has left SIE because of the stop request
The problem is that the SIGP order is already considered completed by
KVM/QEMU when step 1 has been performed and not once both have
completed. In addition we currently don't implement the busy CC so a
kernel has no way of knowing that the store has finished other than
checking the location for the store.
This workaround is based on the fact that for a new SIE entry (via the
added smp restart) a stop with the store status has to be finished
first.
Correct handling of this in KVM/QEMU will need some thought and time.
do I understand correctly that you are here "fixing" the test by not
triggering the KVM bug? Shouldn't we try to trigger as many bugs as
possible instead?
This is not a bug, it's missing code :-)
We trigger a higher number of bugs by running tests and this workaround
does exactly that by letting Thomas use the smp test in the CI again.
Alternatively, we could use report_xfail here to make the test pass, but
still have the problem reported so that we do not forget to fix it later.
Thomas
