Re: [PATCH v3 1/3] s390x: KVM: accept STSI for CPU topology information

David Hildenbrand
2021-08-31T13:59:39Z

On 03.08.21 10:26, Pierre Morel wrote:
> STSI(15.1.x) gives information on the CPU configuration topology.
> Let's accept the interception of STSI with the function code 15 and
> let the userland part of the hypervisor handle it when userland
> support the CPU Topology facility.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
> arch/s390/kvm/priv.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 9928f785c677..8581b6881212 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -856,7 +856,8 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
> if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
>
> - if (fc > 3) {
> + if ((fc > 3 && fc != 15) ||
> + (fc == 15 && !test_kvm_facility(vcpu->kvm, 11))) {
> kvm_s390_set_psw_cc(vcpu, 3);
> return 0;
> }
> @@ -893,6 +894,10 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
> goto out_no_data;
> handle_stsi_3_2_2(vcpu, (void *) mem);
> break;
> + case 15:
> + trace_kvm_s390_handle_stsi(vcpu, fc, sel1, sel2, operand2);
> + insert_stsi_usr_data(vcpu, operand2, ar, fc, sel1, sel2);
> + return -EREMOTE;
> }
> if (kvm_s390_pv_cpu_is_protected(vcpu)) {
> memcpy((void *)sida_origin(vcpu->arch.sie_block), (void *)mem,
>

Sorry, I'm a bit rusty on s390x kvm facility handling.

For test_kvm_facility() to succeed, the facility has to be in both:

a) fac_mask: actually available on the HW and supported by KVM
(kvm_s390_fac_base via FACILITIES_KVM, kvm_s390_fac_ext via
FACILITIES_KVM_CPUMODEL)

b) fac_list: enabled for a VM

AFAIU, facility 11 is neither in FACILITIES_KVM nor
FACILITIES_KVM_CPUMODEL, and I remember it's a hypervisor-managed bit.

So unless we unlock facility 11 in FACILITIES_KVM_CPUMODEL, will
test_kvm_facility(vcpu->kvm, 11) ever successfully trigger here?

I'm pretty sure I am messing something up :)

--
Thanks,

David / dhildenb