Re: [PATCH v3 2/2] target/s390x/kvm: Simplify the GPRs, ACRs, CRs and pr

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Re: [PATCH v3 2/2] target/s390x/kvm: Simplify the GPRs, ACRs, CRs and pr

From:	Cédric Le Goater
Subject:	Re: [PATCH v3 2/2] target/s390x/kvm: Simplify the GPRs, ACRs, CRs and prefix synchronization code
Date:	Tue, 24 Oct 2023 08:11:58 +0200
User-agent:	Mozilla Thunderbird

On 10/11/23 10:05, Thomas Huth wrote:

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.

Signed-off-by: Thomas Huth <thuth@redhat.com>



Reviewed-by: Cédric Le Goater <clg@redhat.com>

Thanks,

C.

---
  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 b3e2eaa2eb..dc76f63d94 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -138,7 +138,6 @@ 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;
@@ -359,7 +358,6 @@ 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);
@@ -466,37 +464,28 @@ 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++) {
@@ -529,6 +518,15 @@ 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;
@@ -575,25 +573,6 @@ 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;
@@ -615,13 +594,6 @@ 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;
  }

@@ -629,8 +601,6 @@ 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;

@@ -638,37 +608,14 @@ 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)) {
@@ -693,11 +640,6 @@ 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;

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[PATCH v3 0/2] target/s390x/kvm: Simplify the synchronization code, Thomas Huth, 2023/10/11
- [PATCH v3 1/2] target/s390x/kvm: Turn KVM_CAP_SYNC_REGS into a hard requirement, Thomas Huth, 2023/10/11
  - Re: [PATCH v3 1/2] target/s390x/kvm: Turn KVM_CAP_SYNC_REGS into a hard requirement, Cédric Le Goater, 2023/10/24
- [PATCH v3 2/2] target/s390x/kvm: Simplify the GPRs, ACRs, CRs and prefix synchronization code, Thomas Huth, 2023/10/11
  - Re: [PATCH v3 2/2] target/s390x/kvm: Simplify the GPRs, ACRs, CRs and prefix synchronization code, Cédric Le Goater <=

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