[PATCH] target/loongarch: Set cpuid CSR register only once with kvm mode

[PATCH] target/loongarch: Set cpuid CSR register only once with kvm mode

[Bibo Mao]

CSR cpuid register is used for routing irq to different vcpus, its
value is kept unchanged since poweron. So it is not necessary to
set CSR cpuid register after system resets, and it is only set at
vm creation stage.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
---
 target/loongarch/kvm/kvm.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
index 84bcdf5f86..2230f029d0 100644
--- a/target/loongarch/kvm/kvm.c
+++ b/target/loongarch/kvm/kvm.c
@@ -250,7 +250,7 @@ static int kvm_loongarch_get_csr(CPUState *cs)
     return ret;
 }
 
-static int kvm_loongarch_put_csr(CPUState *cs)
+static int kvm_loongarch_put_csr(CPUState *cs, int level)
 {
     int ret = 0;
     LoongArchCPU *cpu = LOONGARCH_CPU(cs);
@@ -322,8 +322,11 @@ static int kvm_loongarch_put_csr(CPUState *cs)
     ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_RVACFG),
                            &env->CSR_RVACFG);
 
-    ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_CPUID),
+    /* CPUID is constant after poweron, it should be set only once */
+    if (level >= KVM_PUT_FULL_STATE) {
+        ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_CPUID),
                            &env->CSR_CPUID);
+    }
 
     ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_PRCFG1),
                            &env->CSR_PRCFG1);
@@ -598,7 +601,7 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         return ret;
     }
 
-    ret = kvm_loongarch_put_csr(cs);
+    ret = kvm_loongarch_put_csr(cs, level);
     if (ret) {
         return ret;
     }

base-commit: 977542ded7e6b28d2bc077bcda24568c716e393c
-- 
2.39.3

Re: [PATCH] target/loongarch: Set cpuid CSR register only once with kvm mode

[gaosong]

在 2024/1/15 下午4:51, Bibo Mao 写道:
> CSR cpuid register is used for routing irq to different vcpus, its
> value is kept unchanged since poweron. So it is not necessary to
> set CSR cpuid register after system resets, and it is only set at
> vm creation stage.
>
> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> ---
>   target/loongarch/kvm/kvm.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)

Reviewed-by: Song Gao <gaosong@loongson.cn>

Thanks.
Song Gao
> diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
> index 84bcdf5f86..2230f029d0 100644
> --- a/target/loongarch/kvm/kvm.c
> +++ b/target/loongarch/kvm/kvm.c
> @@ -250,7 +250,7 @@ static int kvm_loongarch_get_csr(CPUState *cs)
>       return ret;
>   }
>   
> -static int kvm_loongarch_put_csr(CPUState *cs)
> +static int kvm_loongarch_put_csr(CPUState *cs, int level)
>   {
>       int ret = 0;
>       LoongArchCPU *cpu = LOONGARCH_CPU(cs);
> @@ -322,8 +322,11 @@ static int kvm_loongarch_put_csr(CPUState *cs)
>       ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_RVACFG),
>                              &env->CSR_RVACFG);
>   
> -    ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_CPUID),
> +    /* CPUID is constant after poweron, it should be set only once */
> +    if (level >= KVM_PUT_FULL_STATE) {
> +        ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_CPUID),
>                              &env->CSR_CPUID);
> +    }
>   
>       ret |= kvm_set_one_reg(cs, KVM_IOC_CSRID(LOONGARCH_CSR_PRCFG1),
>                              &env->CSR_PRCFG1);
> @@ -598,7 +601,7 @@ int kvm_arch_put_registers(CPUState *cs, int level)
>           return ret;
>       }
>   
> -    ret = kvm_loongarch_put_csr(cs);
> +    ret = kvm_loongarch_put_csr(cs, level);
>       if (ret) {
>           return ret;
>       }
>
> base-commit: 977542ded7e6b28d2bc077bcda24568c716e393c