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>

2 files changed, 175 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;
diff --git a/include/asm-s390/kvm_virtio.h b/include/asm-s390/kvm_virtio.h
new file mode 100644
index 000000000000..5c871a990c29
--- /dev/null
+++ b/include/asm-s390/kvm_virtio.h
@@ -0,0 +1,53 @@
+/*
+ * kvm_virtio.h - definition for virtio for kvm on s390
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ *
+ *    Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
+ */
+
+#ifndef __KVM_S390_VIRTIO_H
+#define __KVM_S390_VIRTIO_H
+
+#include <linux/types.h>
+
+struct kvm_device_desc {
+	/* The device type: console, network, disk etc.  Type 0 terminates. */
+	__u8 type;
+	/* The number of virtqueues (first in config array) */
+	__u8 num_vq;
+	/*
+	 * The number of bytes of feature bits.  Multiply by 2: one for host
+	 * features and one for guest acknowledgements.
+	 */
+	__u8 feature_len;
+	/* The number of bytes of the config array after virtqueues. */
+	__u8 config_len;
+	/* A status byte, written by the Guest. */
+	__u8 status;
+	__u8 config[0];
+};
+
+/*
+ * This is how we expect the device configuration field for a virtqueue
+ * to be laid out in config space.
+ */
+struct kvm_vqconfig {
+	/* The token returned with an interrupt. Set by the guest */
+	__u64 token;
+	/* The address of the virtio ring */
+	__u64 address;
+	/* The number of entries in the virtio_ring */
+	__u16 num;
+
+};
+
+#define KVM_S390_VIRTIO_NOTIFY		0
+#define KVM_S390_VIRTIO_RESET		1
+#define KVM_S390_VIRTIO_SET_STATUS	2
+
+#endif