On 6/1/22 5:52 AM, David Hildenbrand wrote:
On 24.05.22 21:02, Matthew Rosato wrote:
The zpci-interp feature is used to specify whether zPCI interpretation is
to be used for this guest.
We have
DEF_FEAT(SIE_PFMFI, "pfmfi", SCLP_CONF_CHAR_EXT, 9, "SIE: PFMF
interpretation facility")
and
DEF_FEAT(SIE_SIGPIF, "sigpif", SCLP_CPU, 12, "SIE: SIGP interpretation
facility")
Should we call this simply "zpcii" or "zpciif" (if the official name
includes "Facility")
This actually controls the use of 2 facilities which really only make
sense together - Maybe just zpcii
Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
hw/s390x/s390-virtio-ccw.c | 1 +
target/s390x/cpu_features_def.h.inc | 1 +
target/s390x/gen-features.c | 2 ++
target/s390x/kvm/kvm.c | 1 +
4 files changed, 5 insertions(+)
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 047cca0487..b33310a135 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -806,6 +806,7 @@ static void ccw_machine_7_0_instance_options(MachineState *machine)
static const S390FeatInit qemu_cpu_feat = { S390_FEAT_LIST_QEMU_V7_0 };
ccw_machine_7_1_instance_options(machine);
+ s390_cpudef_featoff_greater(14, 1, S390_FEAT_ZPCI_INTERP);
s390_set_qemu_cpu_model(0x8561, 15, 1, qemu_cpu_feat);
}
diff --git a/target/s390x/cpu_features_def.h.inc b/target/s390x/cpu_features_def.h.inc
index e86662bb3b..4ade3182aa 100644
--- a/target/s390x/cpu_features_def.h.inc
+++ b/target/s390x/cpu_features_def.h.inc
@@ -146,6 +146,7 @@ DEF_FEAT(SIE_CEI, "cei", SCLP_CPU, 43, "SIE: Conditional-external-interception f
DEF_FEAT(DAT_ENH_2, "dateh2", MISC, 0, "DAT-enhancement facility 2")
DEF_FEAT(CMM, "cmm", MISC, 0, "Collaborative-memory-management facility")
DEF_FEAT(AP, "ap", MISC, 0, "AP instructions installed")
+DEF_FEAT(ZPCI_INTERP, "zpci-interp", MISC, 0, "zPCI interpretation")
How is this feature exposed to the guest, meaning, how can the guest
sense support?
Just a gut feeling: does this toggle enable the host to use
interpretation and the guest cannot really determine the difference
whether it's enabled or not? Then, it's not a guest CPU feature. But
let's hear first what this actually enables :)
This has changed a few times, but collectively we can determine on the
host kernel if it is allowable based upon the availability of certain
facility/sclp bits + the availability of an ioctl interface.
If all of these are available, the host kernel allows zPCI
interpretation, with userspace able to toggle it on/off for the guest
via this feature. When allowed and enabled, 2 ECB bits then get set for
each guest vcpu that enable the associated facilities. The guest
continues to use zPCI instructions in the same manner as before; the
function handles it receives from CLP instructions will look different
but are still used in the same manner.
We don't yet add vsie support of the facilities with this series, so the
corresponding facility and sclp bits aren't forwarded to the guest.
/* Features exposed via the PLO instruction. */
DEF_FEAT(PLO_CL, "plo-cl", PLO, 0, "PLO Compare and load (32 bit in general registers)")
diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c
index c03ec2c9a9..f991646c01 100644
--- a/target/s390x/gen-features.c
+++ b/target/s390x/gen-features.c
@@ -554,6 +554,7 @@ static uint16_t full_GEN14_GA1[] = {
S390_FEAT_HPMA2,
S390_FEAT_SIE_KSS,
S390_FEAT_GROUP_MULTIPLE_EPOCH_PTFF,
+ S390_FEAT_ZPCI_INTERP,
};
#define full_GEN14_GA2 EmptyFeat
@@ -650,6 +651,7 @@ static uint16_t default_GEN14_GA1[] = {
S390_FEAT_GROUP_MSA_EXT_8,
S390_FEAT_MULTIPLE_EPOCH,
S390_FEAT_GROUP_MULTIPLE_EPOCH_PTFF,
+ S390_FEAT_ZPCI_INTERP,
I'm curious, should we really add this to the default model?
This implies that on any setup where we don't have zpci interpretation
support (including missing kernel support), that a basic "-cpu z14" will
no longer work with the new machine type.
If, OTOH, we expect this feature to be around in any sane installation,
then it's good to include it in the
From a hardware perspective, everything will be available on z14 and
later so it's only a question of missing host kernel support (or, you
aren't running in a z14 LPAR). As far as host kernel support, the
expectation is that for a distro release where this QEMU support lands
the associated kernel support would also be backported. I guess that
leaves some awkwardness if one upgrades their distro qemu to a new
release version without picking up the kernel upgrade for some reason..
In that case, you're not totally stuck, you could still use -cpu
z14,zpcii=off (or better yet pick up the associated kernel upgrade...)
The intent is for exploitation of interpretation facilities to become
the default on z14 and later, with the ability to turn it off offered as
a fall-back / backwards compatibility.
If there's a better way to accomplish that, I'm open to suggestion.
