s390: KVM guest: virtio device support, and kvm hypercalls

This patch implements kvm guest kernel support for paravirtualized devices
and contains two parts:
o a basic virtio stub using virtio_ring and external interrupts and hypercalls
o full hypercall implementation in kvm_para.h

Currently we dont have PCI on s390. Making virtio_pci usable for s390 seems
more complicated that providing an own stub. This virtio stub is similar to
the lguest one, the memory for the descriptors and the device detection is made
via additional mapped memory on top of the guest storage. We use an external
interrupt with extint code 0x2603 for host->guest notification.

The hypercall definition uses the diag instruction for issuing a hypercall. The
parameters are written in R2-R7, the hypercall number is written in R1. This is
similar to the system call ABI (svc) which can use R1 for the number and R2-R6
for the parameters.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 122 insertions, 2 deletions

diff --git a/include/asm-s390/kvm_para.h b/include/asm-s390/kvm_para.h
index e9bd3fbe878c..2c503796b619 100644
--- a/include/asm-s390/kvm_para.h
+++ b/include/asm-s390/kvm_para.h
@@ -14,14 +14,134 @@
 #define __S390_KVM_PARA_H
 
 /*
- * No hypercalls for KVM on s390
+ * Hypercalls for KVM on s390. The calling convention is similar to the
+ * s390 ABI, so we use R2-R6 for parameters 1-5. In addition we use R1
+ * as hypercall number and R7 as parameter 6. The return value is
+ * written to R2. We use the diagnose instruction as hypercall. To avoid
+ * conflicts with existing diagnoses for LPAR and z/VM, we do not use
+ * the instruction encoded number, but specify the number in R1 and
+ * use 0x500 as KVM hypercall
+ *
+ * Copyright IBM Corp. 2007,2008
+ * Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
  */
 
+static inline long kvm_hypercall0(unsigned long nr)
+{
+        register unsigned long __nr asm("1") = nr;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr): "memory", "cc");
+        return __rc;
+}
+
+static inline long kvm_hypercall1(unsigned long nr, unsigned long p1)
+{
+        register unsigned long __nr asm("1") = nr;
+        register unsigned long __p1 asm("2") = p1;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr), "0" (__p1) : "memory", "cc");
+        return __rc;
+}
+
+static inline long kvm_hypercall2(unsigned long nr, unsigned long p1,
+                               unsigned long p2)
+{
+        register unsigned long __nr asm("1") = nr;
+        register unsigned long __p1 asm("2") = p1;
+        register unsigned long __p2 asm("3") = p2;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2)
+                      : "memory", "cc");
+        return __rc;
+}
+
+static inline long kvm_hypercall3(unsigned long nr, unsigned long p1,
+                               unsigned long p2, unsigned long p3)
+{
+        register unsigned long __nr asm("1") = nr;
+        register unsigned long __p1 asm("2") = p1;
+        register unsigned long __p2 asm("3") = p2;
+        register unsigned long __p3 asm("4") = p3;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
+                        "d" (__p3) : "memory", "cc");
+        return __rc;
+}
+
+
+static inline long kvm_hypercall4(unsigned long nr, unsigned long p1,
+                               unsigned long p2, unsigned long p3,
+                               unsigned long p4)
+{
+        register unsigned long __nr asm("1") = nr;
+        register unsigned long __p1 asm("2") = p1;
+        register unsigned long __p2 asm("3") = p2;
+        register unsigned long __p3 asm("4") = p3;
+        register unsigned long __p4 asm("5") = p4;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
+                        "d" (__p3), "d" (__p4) : "memory", "cc");
+        return __rc;
+}
+
+static inline long kvm_hypercall5(unsigned long nr, unsigned long p1,
+                               unsigned long p2, unsigned long p3,
+                               unsigned long p4, unsigned long p5)
+{
+        register unsigned long __nr asm("1") = nr;
+        register unsigned long __p1 asm("2") = p1;
+        register unsigned long __p2 asm("3") = p2;
+        register unsigned long __p3 asm("4") = p3;
+        register unsigned long __p4 asm("5") = p4;
+        register unsigned long __p5 asm("6") = p5;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
+                        "d" (__p3), "d" (__p4), "d" (__p5)  : "memory", "cc");
+        return __rc;
+}
+
+static inline long kvm_hypercall6(unsigned long nr, unsigned long p1,
+                               unsigned long p2, unsigned long p3,
+                               unsigned long p4, unsigned long p5,
+                               unsigned long p6)
+{
+        register unsigned long __nr asm("1") = nr;
+        register unsigned long __p1 asm("2") = p1;
+        register unsigned long __p2 asm("3") = p2;
+        register unsigned long __p3 asm("4") = p3;
+        register unsigned long __p4 asm("5") = p4;
+        register unsigned long __p5 asm("6") = p5;
+        register unsigned long __p6 asm("7") = p6;
+        register long __rc asm("2");
+
+        asm volatile ("diag 2,4,0x500\n"
+                      : "=d" (__rc) : "d" (__nr), "0" (__p1), "d" (__p2),
+                        "d" (__p3), "d" (__p4), "d" (__p5), "d" (__p6)
+                      : "memory", "cc");
+        return __rc;
+}
+
+/* kvm on s390 is always paravirtualization enabled */
 static inline int kvm_para_available(void)
 {
-        return 0;
+        return 1;
 }
 
+/* No feature bits are currently assigned for kvm on s390 */
 static inline unsigned int kvm_arch_para_features(void)
 {
         return 0;