On 29.01.19 14:09, Cornelia Huck wrote:
On Thu, 24 Jan 2019 13:59:37 +0100
Michael Mueller <m...@linux.ibm.com> wrote:
Add the Interruption Alert Mask (IAM) to the architecture specific
kvm struct. This mask in the GISA is used to define for which ISC
a GIB alert will be issued.
The functions kvm_s390_gisc_register() and kvm_s390_gisc_unregister()
are used to (un)register a GISC (guest ISC) with a virtual machine and
its GISA.
Upon successful completion, kvm_s390_gisc_register() returns the
ISC to be used for GIB alert interruptions. A negative return code
indicates an error during registration.
Theses functions will be used by other adapter types like AP and PCI to
request pass-through interruption support.
Signed-off-by: Michael Mueller <m...@linux.ibm.com>
---
arch/s390/include/asm/kvm_host.h | 13 +++++
arch/s390/kvm/interrupt.c | 117 +++++++++++++++++++++++++++++++++++++++
2 files changed, 130 insertions(+)
+int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc)
+{
+ struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
+ u8 alert_mask;
+
+ if (!gi->origin)
+ return -ENODEV;
+ if (gisc > MAX_ISC)
+ return -ERANGE;
+
+ spin_lock(&gi->alert.ref_lock);
+ if (gi->alert.ref_count[gisc] == 0) {
If the ref_count is 0 here...
+ alert_mask = gi->alert.mask | 0x80 >> gisc;
+ WRITE_ONCE(gi->alert.mask, alert_mask);
+ }
+ gi->alert.ref_count[gisc]++;
+ if (gi->alert.ref_count[gisc] == 1)
...it will certainly be 1 here, won't it?
Sure, the increment is unconditional and can be done right away.
Thus it is logically the same and now symmetric to the unregister
function:
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index ba314da746b7..f37dfb01c63c 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -2976,11 +2976,11 @@ int kvm_s390_gisc_register(struct kvm *kvm, u32
gisc)
return -ERANGE;
spin_lock(&gi->alert.ref_lock);
- if (gi->alert.ref_count[gisc] == 0)
- gi->alert.mask |= 0x80 >> gisc;
gi->alert.ref_count[gisc]++;
- if (gi->alert.ref_count[gisc] == 1)
+ if (gi->alert.ref_count[gisc] == 1) {
+ gi->alert.mask |= 0x80 >> gisc;
gisa_set_iam(gi->origin, gi->alert.mask);
+ }
spin_unlock(&gi->alert.ref_lock);
return gib->nisc;
Can you do all of the manipulations in a single if branch?
+ gisa_set_iam(gi->origin, alert_mask);
+ spin_unlock(&gi->alert.ref_lock);
+
+ return gib->nisc;
+}
Thanks,
Michael
