[Qemu-devel] [PATCH] s390: use sync regs for register transfer

[Jens Freimann <jfrei@linux.vnet.ibm.com>]

From: Christian Borntraeger <borntraeger@de.ibm.com>

Newer kernels provide the guest registers in kvm_run. Lets use
those if available (i.e. the capability is set). This avoids
ioctls on cpu_synchronize_state making intercepts faster.

In addition, we have now the prefix register, the access registers
the control registers up to date. This helps in certain cases,
e.g. for resolving kernel module addresses with gdb on a guest.

On return, we update the registers according to the level statement,
i.e. we put all registers for KVM_PUT_FULL_STATE and _RESET_STATE.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
---
 target-s390x/kvm.c | 119 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 99 insertions(+), 20 deletions(-)

diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index 07edf93..321ab49 100644
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -67,8 +67,11 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
 
+static int cap_sync_regs;
+
 int kvm_arch_init(KVMState *s)
 {
+    cap_sync_regs = kvm_check_extension(s, KVM_CAP_SYNC_REGS);
     return 0;
 }
 
@@ -88,49 +91,125 @@ void kvm_arch_reset_vcpu(CPUS390XState *env)
     /* FIXME: add code to reset vcpu. */
 }
 
+/* we want to have the prefix, the GPRS, the ACRS and the CRS up to date */
+#define QEMU_NEEDED_REGS  (KVM_SYNC_PREFIX | KVM_SYNC_GPRS | \
+                         KVM_SYNC_ACRS   | KVM_SYNC_CRS)
+
+/* But qemu only changes the GPRS */
+#define QEMU_DIRTY_REGS  (KVM_SYNC_GPRS)
+
 int kvm_arch_put_registers(CPUS390XState *env, int level)
 {
+    struct kvm_sregs sregs;
     struct kvm_regs regs;
     int ret;
     int i;
 
-    ret = kvm_vcpu_ioctl(env, KVM_GET_REGS, &regs);
-    if (ret < 0) {
-        return ret;
-    }
+    /* always save the PSW  and the GPRS*/
+    env->kvm_run->psw_addr = env->psw.addr;
+    env->kvm_run->psw_mask = env->psw.mask;
 
-    for (i = 0; i < 16; i++) {
-        regs.gprs[i] = env->regs[i];
+    if (cap_sync_regs && env->kvm_run->kvm_valid_regs & KVM_SYNC_GPRS) {
+        for (i = 0; i < 16; i++) {
+            env->kvm_run->s.regs.gprs[i] = env->regs[i];
+            env->kvm_run->kvm_dirty_regs |= KVM_SYNC_GPRS;
+        }
+    } else {
+        for (i = 0; i < 16; i++) {
+            regs.gprs[i] = env->regs[i];
+        }
+        ret = kvm_vcpu_ioctl(env, KVM_SET_REGS, &regs);
+        if (ret < 0) {
+            return ret;
+        }
     }
 
-    ret = kvm_vcpu_ioctl(env, KVM_SET_REGS, &regs);
-    if (ret < 0) {
-        return ret;
+    /* Do we need to save more than that? */ 
+    if (level == KVM_PUT_RUNTIME_STATE) {
+        return 0;
     }
 
-    env->kvm_run->psw_addr = env->psw.addr;
-    env->kvm_run->psw_mask = env->psw.mask;
+    if (cap_sync_regs &&
+        env->kvm_run->kvm_valid_regs & KVM_SYNC_ACRS &&
+        env->kvm_run->kvm_valid_regs & KVM_SYNC_CRS) {
+        for (i = 0; i < 16; i++) {
+            env->kvm_run->s.regs.acrs[i] = env->aregs[i];
+            env->kvm_run->s.regs.crs[i] = env->cregs[i];
+        }
+        env->kvm_run->kvm_dirty_regs |= KVM_SYNC_ACRS;
+        env->kvm_run->kvm_dirty_regs |= KVM_SYNC_CRS;
+    } else {
+        for (i = 0; i < 16; i++) {
+            sregs.acrs[i] = env->aregs[i];
+            sregs.crs[i] = env->cregs[i];
+        }
+        ret = kvm_vcpu_ioctl(env, KVM_SET_SREGS, &sregs);
+        if (ret < 0) {
+            return ret;
+        }
+    }
 
-    return ret;
+    /* Finally the prefix */
+    if (cap_sync_regs && env->kvm_run->kvm_valid_regs & KVM_SYNC_PREFIX) {
+        env->kvm_run->s.regs.prefix = env->psa;
+        env->kvm_run->kvm_dirty_regs |= KVM_SYNC_PREFIX;
+    } else {
+        /* prefix is only supported via sync regs */
+    }
+    return 0;
 }
 
 int kvm_arch_get_registers(CPUS390XState *env)
 {
-    int ret;
+    struct kvm_sregs sregs;
     struct kvm_regs regs;
+    int ret;
     int i;
 
-    ret = kvm_vcpu_ioctl(env, KVM_GET_REGS, &regs);
-    if (ret < 0) {
-        return ret;
+    /* get the PSW */
+    env->psw.addr = env->kvm_run->psw_addr;
+    env->psw.mask = env->kvm_run->psw_mask;
+
+    /* the GPRS */
+    if (cap_sync_regs && env->kvm_run->kvm_valid_regs & KVM_SYNC_GPRS) {
+        for (i = 0; i < 16; i++) {
+            env->regs[i] = env->kvm_run->s.regs.gprs[i];
+        }
+    } else {
+        ret = kvm_vcpu_ioctl(env, KVM_GET_REGS, &regs);
+        if (ret < 0) {
+            return ret;
+        }
+         for (i = 0; i < 16; i++) {
+            env->regs[i] = regs.gprs[i];
+        }
     }
 
-    for (i = 0; i < 16; i++) {
-        env->regs[i] = regs.gprs[i];
+    /* The ACRS and CRS */
+    if (cap_sync_regs &&
+        env->kvm_run->kvm_valid_regs & KVM_SYNC_ACRS &&
+        env->kvm_run->kvm_valid_regs & KVM_SYNC_CRS) {
+        for (i = 0; i < 16; i++) {
+            env->aregs[i] = env->kvm_run->s.regs.acrs[i];
+            env->cregs[i] = env->kvm_run->s.regs.crs[i];
+        }
+    } else {
+        ret = kvm_vcpu_ioctl(env, KVM_GET_SREGS, &sregs);
+        if (ret < 0) {
+            return ret;
+        }
+         for (i = 0; i < 16; i++) {
+            env->aregs[i] = sregs.acrs[i];
+            env->cregs[i] = sregs.crs[i];
+        }
     }
 
-    env->psw.addr = env->kvm_run->psw_addr;
-    env->psw.mask = env->kvm_run->psw_mask;
+    /* Finally the prefix */
+    if (cap_sync_regs && env->kvm_run->kvm_valid_regs & KVM_SYNC_PREFIX) {
+        env->psa = env->kvm_run->s.regs.prefix;
+    } else {
+        /* no prefix without sync regs */
+    }
 
     return 0;
 }
-- 
1.7.11.7