[Qemu-devel] [PATCH] s390x/kvm: cleanup partial register handling

[Christian Borntraeger]

From: Dominik Dingel <address@hidden>

Alex, if you have no complaints, I will push this patch to s390-next for 1.8.
This brings s390 back in line with other kvm users and simply use 
cpu_synchronize_state. 

Ok?

Christian

---snip---


The partial register handling (introduced with commits 
420840e58b85f7f4e5493dca3f273566f261090a
3474b679486caa8f6448bae974e131370f360c13 ) aimed to improve intercept handling 
performance.

It made the code more complicated though. During development for life migration
migration/init/reset etc it turned out that this might cause several hard to 
debug programming
errors. With the introduction of ioeventfd (and future irqfd patches) the qemu 
intercept
handlers are no longer hot-path. And therefore the partial register handling 
can be
removed to simplify the code.

Signed-off-by: Dominik Dingel <address@hidden>
CC: Jason J. Herne <address@hidden>
Signed-off-by: Christian Borntraeger <address@hidden>
---
 target-s390x/cpu.h |  17 -------
 target-s390x/kvm.c | 136 +++++++++++++++++++++--------------------------------
 2 files changed, 53 insertions(+), 100 deletions(-)

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 68b5ab7..96c2b4a 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -78,11 +78,6 @@ typedef struct MchkQueue {
     uint16_t type;
 } MchkQueue;
 
-/* Defined values for CPUS390XState.runtime_reg_dirty_mask */
-#define KVM_S390_RUNTIME_DIRTY_NONE     0
-#define KVM_S390_RUNTIME_DIRTY_PARTIAL  1
-#define KVM_S390_RUNTIME_DIRTY_FULL     2
-
 typedef struct CPUS390XState {
     uint64_t regs[16];     /* GP registers */
     CPU_DoubleU fregs[16]; /* FP registers */
@@ -126,13 +121,6 @@ typedef struct CPUS390XState {
     uint64_t cputm;
     uint32_t todpr;
 
-    /* on S390 the runtime register set has two dirty states:
-     * a partial dirty state in which only the registers that
-     * are needed all the time are fetched. And a fully dirty
-     * state in which all runtime registers are fetched.
-     */
-    uint32_t runtime_reg_dirty_mask;
-
     CPU_COMMON
 
     /* reset does memset(0) up to here */
@@ -1076,7 +1064,6 @@ void kvm_s390_io_interrupt(S390CPU *cpu, uint16_t 
subchannel_id,
                            uint32_t io_int_word);
 void kvm_s390_crw_mchk(S390CPU *cpu);
 void kvm_s390_enable_css_support(S390CPU *cpu);
-int kvm_s390_get_registers_partial(CPUState *cpu);
 int kvm_s390_assign_subch_ioeventfd(EventNotifier *notifier, uint32_t sch,
                                     int vq, bool assign);
 int kvm_s390_cpu_restart(S390CPU *cpu);
@@ -1094,10 +1081,6 @@ static inline void kvm_s390_crw_mchk(S390CPU *cpu)
 static inline void kvm_s390_enable_css_support(S390CPU *cpu)
 {
 }
-static inline int kvm_s390_get_registers_partial(CPUState *cpu)
-{
-    return -ENOSYS;
-}
 static inline int kvm_s390_assign_subch_ioeventfd(EventNotifier *notifier,
                                                   uint32_t sch, int vq,
                                                   bool assign)
diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index f7b7726..f60ccdc 100644
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -152,33 +152,30 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         }
     }
 
-    if (env->runtime_reg_dirty_mask == KVM_S390_RUNTIME_DIRTY_FULL) {
-        reg.id = KVM_REG_S390_CPU_TIMER;
-        reg.addr = (__u64)&(env->cputm);
-        ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
-        if (ret < 0) {
-            return ret;
-        }
+    /* Do we need to save more than that? */
+    if (level == KVM_PUT_RUNTIME_STATE) {
+        return 0;
+    }
 
-        reg.id = KVM_REG_S390_CLOCK_COMP;
-        reg.addr = (__u64)&(env->ckc);
-        ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
-        if (ret < 0) {
-            return ret;
-        }
+    reg.id = KVM_REG_S390_CPU_TIMER;
+    reg.addr = (__u64)&(env->cputm);
+    ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
+    if (ret < 0) {
+        return ret;
+    }
 
-        reg.id = KVM_REG_S390_TODPR;
-        reg.addr = (__u64)&(env->todpr);
-        ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
-        if (ret < 0) {
-            return ret;
-        }
+    reg.id = KVM_REG_S390_CLOCK_COMP;
+    reg.addr = (__u64)&(env->ckc);
+    ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
+    if (ret < 0) {
+        return ret;
     }
-    env->runtime_reg_dirty_mask = KVM_S390_RUNTIME_DIRTY_NONE;
 
-    /* Do we need to save more than that? */
-    if (level == KVM_PUT_RUNTIME_STATE) {
-        return 0;
+    reg.id = KVM_REG_S390_TODPR;
+    reg.addr = (__u64)&(env->todpr);
+    ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
+    if (ret < 0) {
+        return ret;
     }
 
     if (cap_sync_regs &&
@@ -216,50 +213,9 @@ int kvm_arch_get_registers(CPUState *cs)
     S390CPU *cpu = S390_CPU(cs);
     CPUS390XState *env = &cpu->env;
     struct kvm_one_reg reg;
-    int r;
-
-    r = kvm_s390_get_registers_partial(cs);
-    if (r < 0) {
-        return r;
-    }
-
-    reg.id = KVM_REG_S390_CPU_TIMER;
-    reg.addr = (__u64)&(env->cputm);
-    r = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
-    if (r < 0) {
-        return r;
-    }
-
-    reg.id = KVM_REG_S390_CLOCK_COMP;
-    reg.addr = (__u64)&(env->ckc);
-    r = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
-    if (r < 0) {
-        return r;
-    }
-
-    reg.id = KVM_REG_S390_TODPR;
-    reg.addr = (__u64)&(env->todpr);
-    r = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
-    if (r < 0) {
-        return r;
-    }
-
-    env->runtime_reg_dirty_mask = KVM_S390_RUNTIME_DIRTY_FULL;
-    return 0;
-}
-
-int kvm_s390_get_registers_partial(CPUState *cs)
-{
-    S390CPU *cpu = S390_CPU(cs);
-    CPUS390XState *env = &cpu->env;
     struct kvm_sregs sregs;
     struct kvm_regs regs;
-    int ret;
-    int i;
-
-    if (env->runtime_reg_dirty_mask) {
-        return 0;
-    }
+    int i, r;
 
     /* get the PSW */
     env->psw.addr = cs->kvm_run->psw_addr;
@@ -271,9 +227,9 @@ int kvm_s390_get_registers_partial(CPUState *cs)
             env->regs[i] = cs->kvm_run->s.regs.gprs[i];
         }
     } else {
-        ret = kvm_vcpu_ioctl(cs, KVM_GET_REGS, &regs);
-        if (ret < 0) {
-            return ret;
+        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];
@@ -289,9 +245,9 @@ int kvm_s390_get_registers_partial(CPUState *cs)
             env->cregs[i] = cs->kvm_run->s.regs.crs[i];
         }
     } else {
-        ret = kvm_vcpu_ioctl(cs, KVM_GET_SREGS, &sregs);
-        if (ret < 0) {
-            return ret;
+        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];
@@ -299,14 +255,33 @@ int kvm_s390_get_registers_partial(CPUState *cs)
         }
     }
 
-    /* Finally the prefix */
+    /* The prefix */
     if (cap_sync_regs && cs->kvm_run->kvm_valid_regs & KVM_SYNC_PREFIX) {
         env->psa = cs->kvm_run->s.regs.prefix;
-    } else {
-        /* no prefix without sync regs */
     }
 
-    env->runtime_reg_dirty_mask = KVM_S390_RUNTIME_DIRTY_PARTIAL;
+    /* One Regs */
+    reg.id = KVM_REG_S390_CPU_TIMER;
+    reg.addr = (__u64)&(env->cputm);
+    r = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
+    if (r < 0) {
+        return r;
+    }
+
+    reg.id = KVM_REG_S390_CLOCK_COMP;
+    reg.addr = (__u64)&(env->ckc);
+    r = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
+    if (r < 0) {
+        return r;
+    }
+
+    reg.id = KVM_REG_S390_TODPR;
+    reg.addr = (__u64)&(env->todpr);
+    r = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &reg);
+    if (r < 0) {
+        return r;
+    }
+
     return 0;
 }
 
@@ -442,15 +417,13 @@ static int kvm_handle_css_inst(S390CPU *cpu, struct 
kvm_run *run,
                                uint8_t ipa0, uint8_t ipa1, uint8_t ipb)
 {
     CPUS390XState *env = &cpu->env;
-    CPUState *cs = CPU(cpu);
 
     if (ipa0 != 0xb2) {
         /* Not handled for now. */
         return -1;
     }
 
-    kvm_s390_get_registers_partial(cs);
-    cs->kvm_vcpu_dirty = true;
+    cpu_synchronize_state(CPU(cpu));
 
     switch (ipa1) {
     case PRIV_XSCH:
@@ -537,11 +510,9 @@ static int handle_priv(S390CPU *cpu, struct kvm_run *run,
 
 static int handle_hypercall(S390CPU *cpu, struct kvm_run *run)
 {
-    CPUState *cs = CPU(cpu);
     CPUS390XState *env = &cpu->env;
 
-    kvm_s390_get_registers_partial(cs);
-    cs->kvm_vcpu_dirty = true;
+    cpu_synchronize_state(CPU(cpu));
     env->regs[2] = s390_virtio_hypercall(env);
 
     return 0;
@@ -767,8 +738,7 @@ static int handle_tsch(S390CPU *cpu)
     struct kvm_run *run = cs->kvm_run;
     int ret;
 
-    kvm_s390_get_registers_partial(cs);
-    cs->kvm_vcpu_dirty = true;
+    cpu_synchronize_state(cs);
 
     ret = ioinst_handle_tsch(env, env->regs[1], run->s390_tsch.ipb);
     if (ret >= 0) {
-- 
1.8.4.2