s390/kvm: Provide a way to prevent reentering SIE

Lets provide functions to prevent KVM from reentering SIE and
to kick cpus out of SIE. We cannot use the common kvm_vcpu_kick code,
since we need to kick out guests in places that hold architecture
specific locks (e.g. pgste lock) which might be necessary on the
other cpus - so no waiting possible.

So lets provide a bit in a private field of the sie control block
that acts as a gate keeper, after we claimed we are in SIE.
Please note that we do not reuse prog0c, since we want to access
that bit without atomic ops.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 962b92e6cf00..9a809f935580 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -71,7 +71,10 @@ struct kvm_s390_sie_block {
         __u8    reserved08[4];          /* 0x0008 */
 #define PROG_IN_SIE (1<<0)
         __u32   prog0c;                 /* 0x000c */
-        __u8    reserved10[24];         /* 0x0010 */
+        __u8    reserved10[16];         /* 0x0010 */
+#define PROG_BLOCK_SIE 0x00000001
+        atomic_t prog20;                /* 0x0020 */
+        __u8    reserved24[4];          /* 0x0024 */
         __u64   cputm;                  /* 0x0028 */
         __u64   ckc;                    /* 0x0030 */
         __u64   epoch;                  /* 0x0038 */