[PULL 24/25] target/s390x/kvm: Simplify the GPRs, ACRs, CRs and prefix synchronization code

[Thomas Huth <thuth@redhat.com>]

KVM_SYNC_GPRS, KVM_SYNC_ACRS, KVM_SYNC_CRS and KVM_SYNC_PREFIX are
available since kernel 3.10. Since we already require at least kernel
3.15 in the s390x KVM code, we can also assume that the KVM_CAP_SYNC_REGS
sync code is always possible for these registers, and remove the
related checks and fallbacks via KVM_SET_REGS and KVM_GET_REGS.

Message-ID: <20231011080538.796999-3-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 target/s390x/kvm/kvm.c | 106 ++++++++++-------------------------------
 1 file changed, 24 insertions(+), 82 deletions(-)

diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index 068e9826e1..0f0e784b2a 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -139,7 +139,6 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
 
-static int cap_sync_regs;
 static int cap_async_pf;
 static int cap_mem_op;
 static int cap_mem_op_extension;
@@ -360,7 +359,6 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         return -1;
     }
 
-    cap_sync_regs = true;
     cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
     cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
     cap_mem_op_extension = kvm_check_extension(s, KVM_CAP_S390_MEM_OP_EXTENSION);
@@ -468,37 +466,28 @@ void kvm_s390_reset_vcpu_normal(S390CPU *cpu)
 
 static int can_sync_regs(CPUState *cs, int regs)
 {
-    return cap_sync_regs && (cs->kvm_run->kvm_valid_regs & regs) == regs;
+    return (cs->kvm_run->kvm_valid_regs & regs) == regs;
 }
 
+#define KVM_SYNC_REQUIRED_REGS (KVM_SYNC_GPRS | KVM_SYNC_ACRS | \
+                                KVM_SYNC_CRS | KVM_SYNC_PREFIX)
+
 int kvm_arch_put_registers(CPUState *cs, int level)
 {
     S390CPU *cpu = S390_CPU(cs);
     CPUS390XState *env = &cpu->env;
-    struct kvm_sregs sregs;
-    struct kvm_regs regs;
     struct kvm_fpu fpu = {};
     int r;
     int i;
 
+    g_assert(can_sync_regs(cs, KVM_SYNC_REQUIRED_REGS));
+
     /* always save the PSW  and the GPRS*/
     cs->kvm_run->psw_addr = env->psw.addr;
     cs->kvm_run->psw_mask = env->psw.mask;
 
-    if (can_sync_regs(cs, KVM_SYNC_GPRS)) {
-        for (i = 0; i < 16; i++) {
-            cs->kvm_run->s.regs.gprs[i] = env->regs[i];
-            cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_GPRS;
-        }
-    } else {
-        for (i = 0; i < 16; i++) {
-            regs.gprs[i] = env->regs[i];
-        }
-        r = kvm_vcpu_ioctl(cs, KVM_SET_REGS, &regs);
-        if (r < 0) {
-            return r;
-        }
-    }
+    memcpy(cs->kvm_run->s.regs.gprs, env->regs, sizeof(cs->kvm_run->s.regs.gprs));
+    cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_GPRS;
 
     if (can_sync_regs(cs, KVM_SYNC_VRS)) {
         for (i = 0; i < 32; i++) {
@@ -531,6 +520,15 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         return 0;
     }
 
+    /*
+     * Access registers, control registers and the prefix - these are
+     * always available via kvm_sync_regs in the kernels that we support
+     */
+    memcpy(cs->kvm_run->s.regs.acrs, env->aregs, sizeof(cs->kvm_run->s.regs.acrs));
+    memcpy(cs->kvm_run->s.regs.crs, env->cregs, sizeof(cs->kvm_run->s.regs.crs));
+    cs->kvm_run->s.regs.prefix = env->psa;
+    cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_ACRS | KVM_SYNC_CRS | KVM_SYNC_PREFIX;
+
     if (can_sync_regs(cs, KVM_SYNC_ARCH0)) {
         cs->kvm_run->s.regs.cputm = env->cputm;
         cs->kvm_run->s.regs.ckc = env->ckc;
@@ -577,25 +575,6 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         }
     }
 
-    /* access registers and control registers*/
-    if (can_sync_regs(cs, KVM_SYNC_ACRS | KVM_SYNC_CRS)) {
-        for (i = 0; i < 16; i++) {
-            cs->kvm_run->s.regs.acrs[i] = env->aregs[i];
-            cs->kvm_run->s.regs.crs[i] = env->cregs[i];
-        }
-        cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_ACRS;
-        cs->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];
-        }
-        r = kvm_vcpu_ioctl(cs, KVM_SET_SREGS, &sregs);
-        if (r < 0) {
-            return r;
-        }
-    }
-
     if (can_sync_regs(cs, KVM_SYNC_GSCB)) {
         memcpy(cs->kvm_run->s.regs.gscb, env->gscb, 32);
         cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_GSCB;
@@ -617,13 +596,6 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_DIAG318;
     }
 
-    /* Finally the prefix */
-    if (can_sync_regs(cs, KVM_SYNC_PREFIX)) {
-        cs->kvm_run->s.regs.prefix = env->psa;
-        cs->kvm_run->kvm_dirty_regs |= KVM_SYNC_PREFIX;
-    } else {
-        /* prefix is only supported via sync regs */
-    }
     return 0;
 }
 
@@ -631,8 +603,6 @@ int kvm_arch_get_registers(CPUState *cs)
 {
     S390CPU *cpu = S390_CPU(cs);
     CPUS390XState *env = &cpu->env;
-    struct kvm_sregs sregs;
-    struct kvm_regs regs;
     struct kvm_fpu fpu;
     int i, r;
 
@@ -640,37 +610,14 @@ int kvm_arch_get_registers(CPUState *cs)
     env->psw.addr = cs->kvm_run->psw_addr;
     env->psw.mask = cs->kvm_run->psw_mask;
 
-    /* the GPRS */
-    if (can_sync_regs(cs, KVM_SYNC_GPRS)) {
-        for (i = 0; i < 16; i++) {
-            env->regs[i] = cs->kvm_run->s.regs.gprs[i];
-        }
-    } else {
-        r = kvm_vcpu_ioctl(cs, KVM_GET_REGS, &regs);
-        if (r < 0) {
-            return r;
-        }
-         for (i = 0; i < 16; i++) {
-            env->regs[i] = regs.gprs[i];
-        }
-    }
+    /* the GPRS, ACRS and CRS */
+    g_assert(can_sync_regs(cs, KVM_SYNC_REQUIRED_REGS));
+    memcpy(env->regs, cs->kvm_run->s.regs.gprs, sizeof(env->regs));
+    memcpy(env->aregs, cs->kvm_run->s.regs.acrs, sizeof(env->aregs));
+    memcpy(env->cregs, cs->kvm_run->s.regs.crs, sizeof(env->cregs));
 
-    /* The ACRS and CRS */
-    if (can_sync_regs(cs, KVM_SYNC_ACRS | KVM_SYNC_CRS)) {
-        for (i = 0; i < 16; i++) {
-            env->aregs[i] = cs->kvm_run->s.regs.acrs[i];
-            env->cregs[i] = cs->kvm_run->s.regs.crs[i];
-        }
-    } else {
-        r = kvm_vcpu_ioctl(cs, KVM_GET_SREGS, &sregs);
-        if (r < 0) {
-            return r;
-        }
-         for (i = 0; i < 16; i++) {
-            env->aregs[i] = sregs.acrs[i];
-            env->cregs[i] = sregs.crs[i];
-        }
-    }
+    /* The prefix */
+    env->psa = cs->kvm_run->s.regs.prefix;
 
     /* Floating point and vector registers */
     if (can_sync_regs(cs, KVM_SYNC_VRS)) {
@@ -695,11 +642,6 @@ int kvm_arch_get_registers(CPUState *cs)
         env->fpc = fpu.fpc;
     }
 
-    /* The prefix */
-    if (can_sync_regs(cs, KVM_SYNC_PREFIX)) {
-        env->psa = cs->kvm_run->s.regs.prefix;
-    }
-
     if (can_sync_regs(cs, KVM_SYNC_ARCH0)) {
         env->cputm = cs->kvm_run->s.regs.cputm;
         env->ckc = cs->kvm_run->s.regs.ckc;
-- 
2.41.0