[PATCH v2 0/3] accel/kvm: Cleanups around kvm_arch_put_registers()

[PATCH v2 0/3] accel/kvm: Cleanups around kvm_arch_put_registers()

[Philippe Mathieu-Daudé]

Extracted from a bigger series aiming to make accelerator
synchronization of vcpu state slightly clearer. Here KVM
patches around kvm_arch_put_registers():
- Move KVM_PUT_[RESET|RUNTIME|FULL]_STATE to an enum
- Factor common code out of kvm_cpu_synchronize_post_*()

Philippe Mathieu-Daudé (3):
  accel/kvm: Do not expect more then KVM_PUT_FULL_STATE
  accel/kvm: Introduce KvmPutState enum
  accel/kvm: Factor kvm_cpu_synchronize_put() out

 include/system/kvm.h       | 16 +++++++------
 accel/kvm/kvm-all.c        | 47 +++++++++++++++-----------------------
 target/i386/kvm/kvm.c      |  6 ++---
 target/loongarch/kvm/kvm.c |  8 +++----
 target/mips/kvm.c          |  6 ++---
 target/ppc/kvm.c           |  2 +-
 target/riscv/kvm/kvm-cpu.c |  2 +-
 target/s390x/kvm/kvm.c     |  2 +-
 8 files changed, 41 insertions(+), 48 deletions(-)

-- 
2.51.0

[PATCH v2 1/3] accel/kvm: Do not expect more then KVM_PUT_FULL_STATE

[Philippe Mathieu-Daudé]

KVM_PUT_FULL_STATE is the highest level defined so far in
"system/kvm.h"; do not check for more.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
---
 target/loongarch/kvm/kvm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
index e5ea2dba9da..45292edcb1c 100644
--- a/target/loongarch/kvm/kvm.c
+++ b/target/loongarch/kvm/kvm.c
@@ -397,7 +397,7 @@ static int kvm_loongarch_put_csr(CPUState *cs, int level)
                            &env->CSR_RVACFG);
 
     /* CPUID is constant after poweron, it should be set only once */
-    if (level >= KVM_PUT_FULL_STATE) {
+    if (level == KVM_PUT_FULL_STATE) {
         ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_CPUID),
                            &env->CSR_CPUID);
     }
@@ -801,7 +801,7 @@ int kvm_arch_put_registers(CPUState *cs, int level, Error **errp)
         once = 1;
     }
 
-    if (level >= KVM_PUT_FULL_STATE) {
+    if (level == KVM_PUT_FULL_STATE) {
         /*
          * only KVM_PUT_FULL_STATE is required, kvm kernel will clear
          * guest_addr for KVM_PUT_RESET_STATE
-- 
2.51.0

[PATCH v2 2/3] accel/kvm: Introduce KvmPutState enum

[Philippe Mathieu-Daudé]

Join the 3 KVM_PUT_*_STATE definitions in a single enum.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
---
 include/system/kvm.h       | 16 +++++++++-------
 target/i386/kvm/kvm.c      |  6 +++---
 target/loongarch/kvm/kvm.c |  4 ++--
 target/mips/kvm.c          |  6 +++---
 target/ppc/kvm.c           |  2 +-
 target/riscv/kvm/kvm-cpu.c |  2 +-
 target/s390x/kvm/kvm.c     |  2 +-
 7 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/include/system/kvm.h b/include/system/kvm.h
index 4fc09e38910..8f9eecf044c 100644
--- a/include/system/kvm.h
+++ b/include/system/kvm.h
@@ -340,14 +340,16 @@ int kvm_arch_process_async_events(CPUState *cpu);
 
 int kvm_arch_get_registers(CPUState *cpu, Error **errp);
 
-/* state subset only touched by the VCPU itself during runtime */
-#define KVM_PUT_RUNTIME_STATE   1
-/* state subset modified during VCPU reset */
-#define KVM_PUT_RESET_STATE     2
-/* full state set, modified during initialization or on vmload */
-#define KVM_PUT_FULL_STATE      3
+typedef enum kvm_put_state {
+    /* state subset only touched by the VCPU itself during runtime */
+    KVM_PUT_RUNTIME_STATE = 1,
+    /* state subset modified during VCPU reset */
+    KVM_PUT_RESET_STATE = 2,
+    /* full state set, modified during initialization or on vmload */
+    KVM_PUT_FULL_STATE = 3,
+} KvmPutState;
 
-int kvm_arch_put_registers(CPUState *cpu, int level, Error **errp);
+int kvm_arch_put_registers(CPUState *cpu, KvmPutState level, Error **errp);
 
 int kvm_arch_get_default_type(MachineState *ms);
 
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 6a3a1c1ed8e..d06f55938cd 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -3911,7 +3911,7 @@ static void kvm_init_msrs(X86CPU *cpu)
     assert(kvm_buf_set_msrs(cpu) == 0);
 }
 
-static int kvm_put_msrs(X86CPU *cpu, int level)
+static int kvm_put_msrs(X86CPU *cpu, KvmPutState level)
 {
     CPUX86State *env = &cpu->env;
     int i;
@@ -5031,7 +5031,7 @@ static int kvm_get_apic(X86CPU *cpu)
     return 0;
 }
 
-static int kvm_put_vcpu_events(X86CPU *cpu, int level)
+static int kvm_put_vcpu_events(X86CPU *cpu, KvmPutState level)
 {
     CPUState *cs = CPU(cpu);
     CPUX86State *env = &cpu->env;
@@ -5274,7 +5274,7 @@ static int kvm_get_nested_state(X86CPU *cpu)
     return ret;
 }
 
-int kvm_arch_put_registers(CPUState *cpu, int level, Error **errp)
+int kvm_arch_put_registers(CPUState *cpu, KvmPutState level, Error **errp)
 {
     X86CPU *x86_cpu = X86_CPU(cpu);
     int ret;
diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
index 45292edcb1c..32cd7c5d003 100644
--- a/target/loongarch/kvm/kvm.c
+++ b/target/loongarch/kvm/kvm.c
@@ -325,7 +325,7 @@ static int kvm_loongarch_get_csr(CPUState *cs)
     return ret;
 }
 
-static int kvm_loongarch_put_csr(CPUState *cs, int level)
+static int kvm_loongarch_put_csr(CPUState *cs, KvmPutState level)
 {
     int ret = 0;
     CPULoongArchState *env = cpu_env(cs);
@@ -763,7 +763,7 @@ int kvm_arch_get_registers(CPUState *cs, Error **errp)
     return ret;
 }
 
-int kvm_arch_put_registers(CPUState *cs, int level, Error **errp)
+int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp)
 {
     int ret;
     static int once;
diff --git a/target/mips/kvm.c b/target/mips/kvm.c
index 450947c3fa5..912cd5dfa0e 100644
--- a/target/mips/kvm.c
+++ b/target/mips/kvm.c
@@ -590,7 +590,7 @@ static void kvm_mips_update_state(void *opaque, bool running, RunState state)
     }
 }
 
-static int kvm_mips_put_fpu_registers(CPUState *cs, int level)
+static int kvm_mips_put_fpu_registers(CPUState *cs, KvmPutState level)
 {
     CPUMIPSState *env = cpu_env(cs);
     int err, ret = 0;
@@ -749,7 +749,7 @@ static int kvm_mips_get_fpu_registers(CPUState *cs)
 }
 
 
-static int kvm_mips_put_cp0_registers(CPUState *cs, int level)
+static int kvm_mips_put_cp0_registers(CPUState *cs, KvmPutState level)
 {
     CPUMIPSState *env = cpu_env(cs);
     int err, ret = 0;
@@ -1177,7 +1177,7 @@ static int kvm_mips_get_cp0_registers(CPUState *cs)
     return ret;
 }
 
-int kvm_arch_put_registers(CPUState *cs, int level, Error **errp)
+int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp)
 {
     CPUMIPSState *env = cpu_env(cs);
     struct kvm_regs regs;
diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index 2521ff65c6c..cd60893a17d 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -907,7 +907,7 @@ int kvmppc_put_books_sregs(PowerPCCPU *cpu)
     return kvm_vcpu_ioctl(CPU(cpu), KVM_SET_SREGS, &sregs);
 }
 
-int kvm_arch_put_registers(CPUState *cs, int level, Error **errp)
+int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp)
 {
     PowerPCCPU *cpu = POWERPC_CPU(cs);
     CPUPPCState *env = &cpu->env;
diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
index 187c2c9501e..75ca3fb9fd9 100644
--- a/target/riscv/kvm/kvm-cpu.c
+++ b/target/riscv/kvm/kvm-cpu.c
@@ -1369,7 +1369,7 @@ int kvm_riscv_sync_mpstate_to_kvm(RISCVCPU *cpu, int state)
     return 0;
 }
 
-int kvm_arch_put_registers(CPUState *cs, int level, Error **errp)
+int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp)
 {
     int ret = 0;
 
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index 491cc5f9756..916dac1f14e 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -468,7 +468,7 @@ static int can_sync_regs(CPUState *cs, int 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, Error **errp)
+int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp)
 {
     CPUS390XState *env = cpu_env(cs);
     struct kvm_fpu fpu = {};
-- 
2.51.0

[PATCH v2 3/3] accel/kvm: Factor kvm_cpu_synchronize_put() out

[Philippe Mathieu-Daudé]

The same code is duplicated 3 times: factor a common method.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/kvm/kvm-all.c | 47 ++++++++++++++++++---------------------------
 1 file changed, 19 insertions(+), 28 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 58802f7c3cc..56031925c4e 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2937,22 +2937,32 @@ void kvm_cpu_synchronize_state(CPUState *cpu)
     }
 }
 
-static void do_kvm_cpu_synchronize_post_reset(CPUState *cpu, run_on_cpu_data arg)
+static bool kvm_cpu_synchronize_put(CPUState *cpu, KvmPutState state,
+                                    const char *desc)
 {
     Error *err = NULL;
-    int ret = kvm_arch_put_registers(cpu, KVM_PUT_RESET_STATE, &err);
+    int ret = kvm_arch_put_registers(cpu, state, &err);
     if (ret) {
         if (err) {
-            error_reportf_err(err, "Restoring resisters after reset: ");
+            error_reportf_err(err, "Restoring resisters %s: ", desc);
         } else {
-            error_report("Failed to put registers after reset: %s",
+            error_report("Failed to put registers %s: %s", desc,
                          strerror(-ret));
         }
-        cpu_dump_state(cpu, stderr, CPU_DUMP_CODE);
-        vm_stop(RUN_STATE_INTERNAL_ERROR);
+        return false;
     }
 
     cpu->vcpu_dirty = false;
+
+    return true;
+}
+
+static void do_kvm_cpu_synchronize_post_reset(CPUState *cpu, run_on_cpu_data arg)
+{
+    if (!kvm_cpu_synchronize_put(cpu, KVM_PUT_RESET_STATE, "after reset")) {
+        cpu_dump_state(cpu, stderr, CPU_DUMP_CODE);
+        vm_stop(RUN_STATE_INTERNAL_ERROR);
+    }
 }
 
 void kvm_cpu_synchronize_post_reset(CPUState *cpu)
@@ -2966,19 +2976,9 @@ void kvm_cpu_synchronize_post_reset(CPUState *cpu)
 
 static void do_kvm_cpu_synchronize_post_init(CPUState *cpu, run_on_cpu_data arg)
 {
-    Error *err = NULL;
-    int ret = kvm_arch_put_registers(cpu, KVM_PUT_FULL_STATE, &err);
-    if (ret) {
-        if (err) {
-            error_reportf_err(err, "Putting registers after init: ");
-        } else {
-            error_report("Failed to put registers after init: %s",
-                         strerror(-ret));
-        }
+    if (!kvm_cpu_synchronize_put(cpu, KVM_PUT_FULL_STATE, "after init")) {
         exit(1);
     }
-
-    cpu->vcpu_dirty = false;
 }
 
 void kvm_cpu_synchronize_post_init(CPUState *cpu)
@@ -3168,20 +3168,11 @@ int kvm_cpu_exec(CPUState *cpu)
         MemTxAttrs attrs;
 
         if (cpu->vcpu_dirty) {
-            Error *err = NULL;
-            ret = kvm_arch_put_registers(cpu, KVM_PUT_RUNTIME_STATE, &err);
-            if (ret) {
-                if (err) {
-                    error_reportf_err(err, "Putting registers after init: ");
-                } else {
-                    error_report("Failed to put registers after init: %s",
-                                 strerror(-ret));
-                }
+            if (!kvm_cpu_synchronize_put(cpu, KVM_PUT_RUNTIME_STATE,
+                                         "at runtime")) {
                 ret = -1;
                 break;
             }
-
-            cpu->vcpu_dirty = false;
         }
 
         kvm_arch_pre_run(cpu, run);
-- 
2.51.0

Re: [PATCH v2 0/3] accel/kvm: Cleanups around kvm_arch_put_registers()

[Andrew Jones]

On Wed, Oct 08, 2025 at 06:07:11AM +0200, Philippe Mathieu-Daudé wrote:
> Extracted from a bigger series aiming to make accelerator
> synchronization of vcpu state slightly clearer. Here KVM
> patches around kvm_arch_put_registers():
> - Move KVM_PUT_[RESET|RUNTIME|FULL]_STATE to an enum
> - Factor common code out of kvm_cpu_synchronize_post_*()
> 
> Philippe Mathieu-Daudé (3):
>   accel/kvm: Do not expect more then KVM_PUT_FULL_STATE
>   accel/kvm: Introduce KvmPutState enum
>   accel/kvm: Factor kvm_cpu_synchronize_put() out
> 
>  include/system/kvm.h       | 16 +++++++------
>  accel/kvm/kvm-all.c        | 47 +++++++++++++++-----------------------
>  target/i386/kvm/kvm.c      |  6 ++---
>  target/loongarch/kvm/kvm.c |  8 +++----
>  target/mips/kvm.c          |  6 ++---
>  target/ppc/kvm.c           |  2 +-
>  target/riscv/kvm/kvm-cpu.c |  2 +-
>  target/s390x/kvm/kvm.c     |  2 +-
>  8 files changed, 41 insertions(+), 48 deletions(-)
> 
> -- 
> 2.51.0
> 
>

For the series,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Re: [PATCH v2 0/3] accel/kvm: Cleanups around kvm_arch_put_registers()

[Paolo Bonzini]

Queued patches 2-3, thanks.

For patch 1, I think it's better to have consistency in the use of >=.

Paolo