KVM: s390: sie intercept handling

This path introduces handling of sie intercepts in three flavors: Intercepts
are either handled completely in-kernel by kvm_handle_sie_intercept(),
or passed to userspace with corresponding data in struct kvm_run in case
kvm_handle_sie_intercept() returns -ENOTSUPP.
In case of partial execution in kernel with the need of userspace support,
kvm_handle_sie_intercept() may choose to set up struct kvm_run and return
-EREMOTE.

The trivial intercept reasons are handled in this patch:
handle_noop() just does nothing for intercepts that don't require our support
  at all
handle_stop() is called when a cpu enters stopped state, and it drops out to
  userland after updating our vcpu state
handle_validity() faults in the cpu lowcore if needed, or passes the request
  to userland

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

4 files changed, 133 insertions, 2 deletions

diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
index 0d8d1135a27..27882b35ef0 100644
--- a/arch/s390/kvm/Makefile
+++ b/arch/s390/kvm/Makefile
@@ -10,5 +10,5 @@ common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o)
 
 EXTRA_CFLAGS += -Ivirt/kvm -Iarch/s390/kvm
 
-kvm-objs := $(common-objs) kvm-s390.o sie64a.o
+kvm-objs := $(common-objs) kvm-s390.o sie64a.o intercept.o
 obj-$(CONFIG_KVM) += kvm.o
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
new file mode 100644
index 00000000000..e757230b982
--- /dev/null
+++ b/arch/s390/kvm/intercept.c
@@ -0,0 +1,80 @@
+/*
+ * intercept.c - in-kernel handling for sie intercepts
+ *
+ * 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): Carsten Otte <cotte@de.ibm.com>
+ *               Christian Borntraeger <borntraeger@de.ibm.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/errno.h>
+#include <linux/pagemap.h>
+
+#include <asm/kvm_host.h>
+
+#include "kvm-s390.h"
+
+static int handle_noop(struct kvm_vcpu *vcpu)
+{
+        switch (vcpu->arch.sie_block->icptcode) {
+        case 0x10:
+                vcpu->stat.exit_external_request++;
+                break;
+        case 0x14:
+                vcpu->stat.exit_external_interrupt++;
+                break;
+        default:
+                break; /* nothing */
+        }
+        return 0;
+}
+
+static int handle_stop(struct kvm_vcpu *vcpu)
+{
+        vcpu->stat.exit_stop_request++;
+        VCPU_EVENT(vcpu, 3, "%s", "cpu stopped");
+        atomic_clear_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
+        return -ENOTSUPP;
+}
+
+static int handle_validity(struct kvm_vcpu *vcpu)
+{
+        int viwhy = vcpu->arch.sie_block->ipb >> 16;
+        vcpu->stat.exit_validity++;
+        if (viwhy == 0x37) {
+                fault_in_pages_writeable((char __user *)
+                                         vcpu->kvm->arch.guest_origin +
+                                         vcpu->arch.sie_block->prefix,
+                                         PAGE_SIZE);
+                return 0;
+        }
+        VCPU_EVENT(vcpu, 2, "unhandled validity intercept code %d",
+                   viwhy);
+        return -ENOTSUPP;
+}
+
+static const intercept_handler_t intercept_funcs[0x48 >> 2] = {
+        [0x00 >> 2] = handle_noop,
+        [0x10 >> 2] = handle_noop,
+        [0x14 >> 2] = handle_noop,
+        [0x20 >> 2] = handle_validity,
+        [0x28 >> 2] = handle_stop,
+};
+
+int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
+{
+        intercept_handler_t func;
+        u8 code = vcpu->arch.sie_block->icptcode;
+
+        if (code & 3 || code > 0x48)
+                return -ENOTSUPP;
+        func = intercept_funcs[code >> 2];
+        if (func)
+                return func(vcpu);
+        return -ENOTSUPP;
+}
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6e1e1d39ae1..a906499214b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -23,12 +23,17 @@
 #include <asm/lowcore.h>
 #include <asm/pgtable.h>
 
+#include "kvm-s390.h"
 #include "gaccess.h"
 
 #define VCPU_STAT(x) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "userspace_handled", VCPU_STAT(exit_userspace) },
+        { "exit_validity", VCPU_STAT(exit_validity) },
+        { "exit_stop_request", VCPU_STAT(exit_stop_request) },
+        { "exit_external_request", VCPU_STAT(exit_external_request) },
+        { "exit_external_interrupt", VCPU_STAT(exit_external_interrupt) },
         { NULL }
 };
 
@@ -380,6 +385,7 @@ static void __vcpu_run(struct kvm_vcpu *vcpu)
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
+        int rc;
         sigset_t sigsaved;
 
         vcpu_load(vcpu);
@@ -389,7 +395,45 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
         atomic_set_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
 
-        __vcpu_run(vcpu);
+        switch (kvm_run->exit_reason) {
+        case KVM_EXIT_S390_SIEIC:
+                vcpu->arch.sie_block->gpsw.mask = kvm_run->s390_sieic.mask;
+                vcpu->arch.sie_block->gpsw.addr = kvm_run->s390_sieic.addr;
+                break;
+        case KVM_EXIT_UNKNOWN:
+        case KVM_EXIT_S390_RESET:
+                break;
+        default:
+                BUG();
+        }
+
+        might_sleep();
+
+        do {
+                __vcpu_run(vcpu);
+
+                rc = kvm_handle_sie_intercept(vcpu);
+        } while (!signal_pending(current) && !rc);
+
+        if (signal_pending(current) && !rc)
+                rc = -EINTR;
+
+        if (rc == -ENOTSUPP) {
+                /* intercept cannot be handled in-kernel, prepare kvm-run */
+                kvm_run->exit_reason         = KVM_EXIT_S390_SIEIC;
+                kvm_run->s390_sieic.icptcode = vcpu->arch.sie_block->icptcode;
+                kvm_run->s390_sieic.mask     = vcpu->arch.sie_block->gpsw.mask;
+                kvm_run->s390_sieic.addr     = vcpu->arch.sie_block->gpsw.addr;
+                kvm_run->s390_sieic.ipa      = vcpu->arch.sie_block->ipa;
+                kvm_run->s390_sieic.ipb      = vcpu->arch.sie_block->ipb;
+                rc = 0;
+        }
+
+        if (rc == -EREMOTE) {
+                /* intercept was handled, but userspace support is needed
+                 * kvm_run has been prepared by the handler */
+                rc = 0;
+        }
 
         if (vcpu->sigset_active)
                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index ed64a22ca86..5b82527b7f8 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -13,6 +13,13 @@
 
 #ifndef ARCH_S390_KVM_S390_H
 #define ARCH_S390_KVM_S390_H
+
+#include <linux/kvm_host.h>
+
+typedef int (*intercept_handler_t)(struct kvm_vcpu *vcpu);
+
+int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu);
+
 #define VM_EVENT(d_kvm, d_loglevel, d_string, d_args...)\
 do { \
         debug_sprintf_event(d_kvm->arch.dbf, d_loglevel, d_string "\n", \