On 18.01.18 15:33, David Hildenbrand wrote:
On 18.01.2018 15:29, Michael Mueller wrote:
On 17.01.18 15:35, David Hildenbrand wrote:
On 16.01.2018 21:02, Christian Borntraeger wrote:
From: Michael Mueller <mimu@xxxxxxxxxxxxxxxxxx>
The patch implements routines to access the GISA to test and modify
its Interruption Pending Mask (IPM) from the host side.
Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
arch/s390/kvm/interrupt.c | 23 +++++++++++++++++++++++
arch/s390/kvm/kvm-s390.h | 4 ++++
2 files changed, 27 insertions(+)
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index b94173560dcf..dfdecff302d2 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -2682,3 +2682,26 @@ int kvm_s390_get_irq_state(struct kvm_vcpu *vcpu, __u8 __user *buf, int len)
return n;
}
+
+#define IPM_BIT_OFFSET (offsetof(struct kvm_s390_gisa, ipm) * 8)
8 -> BITS_PER_BYTE, but ...
Am I wrong or can we only modify the 8 ipm bits this way? But we
want/have to do it in an atomic fashion?
Using an unsigned long seems wrong, because we "rewrite" more than we
should. Esp. everything beyond ipm. oi / ni and friends are not
available on older machines.
What about something as simple as the following
+void kvm_s390_gisa_set_ipm_gisc(struct kvm_s390_gisa *gisa, u8 gisc)
+{
+ u8 value = (0x80 >> gisc);
+
+ __sync_fetch_and_or(&gisa->ipm, value);
+}
+
Nobody is using this compiler build-in in the kernel and a quick compile
shows that it produces an ORK and CS instead of a LAOG beside a lot of
supporting instructions. Unfortunately it's not saving what you promise
... ;) Will not change.
Using unsigned long * bitmap operations to modify an u8 type atomically
just seems very very wrong >
I have to reconsider this...
--
To unsubscribe from this list: send the line "unsubscribe linux-s390" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
