On Thu, Jul 15 2021, David Hildenbrand <david@xxxxxxxxxx> wrote:
On 14.07.21 17:25, 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.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
arch/s390/kvm/priv.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 9928f785c677..4ab5f8b7780e 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -856,7 +856,7 @@ 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) {
kvm_s390_set_psw_cc(vcpu, 3);
return 0;
}
@@ -893,6 +893,15 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
goto out_no_data;
handle_stsi_3_2_2(vcpu, (void *) mem);
break;
+ case 15:
+ if (sel1 != 1 || sel2 < 2 || sel2 > 6)
+ goto out_no_data;
+ if (vcpu->kvm->arch.user_stsi) {
+ insert_stsi_usr_data(vcpu, operand2, ar, fc, sel1, sel2);
+ return -EREMOTE;
This bypasses the trace event further down.
+ }
+ kvm_s390_set_psw_cc(vcpu, 3);
+ return 0;
}
if (kvm_s390_pv_cpu_is_protected(vcpu)) {
memcpy((void *)sida_origin(vcpu->arch.sie_block), (void *)mem,
1. Setting GPRS to 0
I was wondering why we have the "vcpu->run->s.regs.gprs[0] = 0;"
for existing fc 1,2,3 in case we set cc=0.
Looking at the doc, all I find is:
"CC 0: Requested configuration-level number placed in
general register 0 or requested SYSIB informa-
tion stored"
But I don't find where it states that we are supposed to set
general register 0 to 0. Wouldn't we also have to do it for
fc=15 or for none?
If fc 1,2,3 and 15 are to be handled equally, I suggest the following:
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 9928f785c677..6eb86fa58b0b 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -893,17 +893,23 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
goto out_no_data;
handle_stsi_3_2_2(vcpu, (void *) mem);
break;
+ case 15:
+ if (sel1 != 1 || sel2 < 2 || sel2 > 6)
+ goto out_no_data;
+ break;
}
- if (kvm_s390_pv_cpu_is_protected(vcpu)) {
- memcpy((void *)sida_origin(vcpu->arch.sie_block), (void *)mem,
- PAGE_SIZE);
- rc = 0;
- } else {
- rc = write_guest(vcpu, operand2, ar, (void *)mem, PAGE_SIZE);
- }
- if (rc) {
- rc = kvm_s390_inject_prog_cond(vcpu, rc);
- goto out;
+ if (mem) {
+ if (kvm_s390_pv_cpu_is_protected(vcpu)) {
+ memcpy((void *)sida_origin(vcpu->arch.sie_block),
+ (void *)mem, PAGE_SIZE);
+ } else {
+ rc = write_guest(vcpu, operand2, ar, (void *)mem,
+ PAGE_SIZE);
+ if (rc) {
+ rc = kvm_s390_inject_prog_cond(vcpu, rc);
+ goto out;
+ }
+ }
}
if (vcpu->kvm->arch.user_stsi) {
insert_stsi_usr_data(vcpu, operand2, ar, fc, sel1, sel2);
Something like that sounds good, the code is getting a bit convoluted.
2. maximum-MNest facility
"
1. If the maximum-MNest facility is installed and
selector 2 exceeds the nonzero model-depen-
dent maximum-selector-2 value."
2. If the maximum-MNest facility is not installed and
selector 2 is not specified as two.
"
We will we be handling the presence/absence of the maximum-MNest facility
(for our guest?) in QEMU, corect?
I do wonder if we should just let any fc=15 go to user space let the whole
sel1 / sel2 checking be handled there. I don't think it's a fast path after all.
But no strong opinion.
If that makes handling easier, I think it would be a good idea.
How do we identify availability of maximum-MNest facility?
3. User space awareness
How can user space identify that we actually forward these intercepts?
How can it enable them? The old KVM_CAP_S390_USER_STSI capability
is not sufficient.
Why do you think that it is not sufficient? USER_STSI basically says
"you may get an exit that tells you about a buffer to fill in some more
data for a stsi command, and we also tell you which call". If userspace
does not know what to add for a certain call, it is free to just do
nothing, and if it does not get some calls it would support, that should
not be a problem, either?
