On 12/7/20 3:09 PM, Christian Borntraeger wrote: > > > On 07.12.20 21:06, Collin Walling wrote: >> On 12/7/20 2:32 PM, Christian Borntraeger wrote: >>> On 07.12.20 16:41, Collin Walling wrote: >>>> The DIAGNOSE 0x0318 instruction, unique to s390x, is a privileged call >>>> that must be intercepted via SIE, handled in userspace, and the >>>> information set by the instruction is communicated back to KVM. >>>> >>>> To test the instruction interception, an ad-hoc handler is defined which >>>> simply has a VM execute the instruction and then userspace will extract >>>> the necessary info. The handler is defined such that the instruction >>>> invocation occurs only once. It is up to the caller to determine how the >>>> info returned by this handler should be used. >>>> >>>> The diag318 info is communicated from userspace to KVM via a sync_regs >>>> call. This is tested During a sync_regs test, where the diag318 info is >>>> requested via the handler, then the info is stored in the appropriate >>>> register in KVM via a sync registers call. >>>> >>>> If KVM does not support diag318, then the tests will print a message >>>> stating that diag318 was skipped, and the asserts will simply test >>>> against a value of 0. >>>> >>>> Signed-off-by: Collin Walling <walling@xxxxxxxxxxxxx> >>> >>> Interestingly enough, this testcase actually trigger a bug: >>> While we gracefully handle this (no crash) >>> debugfs: Directory 'kvm-200206' with parent 's390dbf' already present! >>> is certainly not ideal.... >>> >> >> Odd... I wonder what triggered this behavior? >> >> I run my tests with a simple command: >> >> make summary=0 TARGETS=kvm kselftest >> >> This must have something to do with spinning up another VM to get the >> diag318 data. I think if I have the sync_regs test call the diag handler >> first, and then have the sync regs create a VM, that might solve that >> issue... > > Yes, the s390dbf code will try to create a file named kvm-%pid. With > 2 VMs the 2nd one fails. Luckily the kvm will be created anyway and > also the shutdown seems to be fine, still.... > >> >> May I ask how you encountered this bug so I may replicate in on my end? > > I just did > make TARGETS=kvm selftests > > and then the error is on dmesg. > Thanks. v5 with fix incoming. -- Regards, Collin Stay safe and stay healthy
