Re: [PATCH 4/9] mips/kvm: Implement Config CP0 registers

[Leon Alrae <leon.alrae@imgtec.com>]

On 11/03/2015 15:22, James Hogan wrote:
> Implement saving and restoring to KVM state of the Config CP0 registers
> (namely Config, Config1, Config2, Config3, Config4, and Config5). These
> control the features available to a guest, and a few of the fields will
> soon be writeable by a guest so QEMU needs to know about them so as not
> to clobber them on migration/savevm.
> 
> Signed-off-by: James Hogan <james.hogan@imgtec.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Leon Alrae <leon.alrae@imgtec.com>
> Cc: Aurelien Jarno <aurelien@aurel32.net>
> ---
>  target-mips/kvm.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 108 insertions(+)
> 
> diff --git a/target-mips/kvm.c b/target-mips/kvm.c
> index 730c67e247d8..b8813a2722a3 100644
> --- a/target-mips/kvm.c
> +++ b/target-mips/kvm.c
> @@ -223,6 +223,12 @@ int kvm_mips_set_ipi_interrupt(MIPSCPU *cpu, int irq, int level)
>  #define KVM_REG_MIPS_CP0_CAUSE          MIPS_CP0_32(13, 0)
>  #define KVM_REG_MIPS_CP0_EPC            MIPS_CP0_64(14, 0)
>  #define KVM_REG_MIPS_CP0_PRID           MIPS_CP0_32(15, 0)
> +#define KVM_REG_MIPS_CP0_CONFIG         MIPS_CP0_32(16, 0)
> +#define KVM_REG_MIPS_CP0_CONFIG1        MIPS_CP0_32(16, 1)
> +#define KVM_REG_MIPS_CP0_CONFIG2        MIPS_CP0_32(16, 2)
> +#define KVM_REG_MIPS_CP0_CONFIG3        MIPS_CP0_32(16, 3)
> +#define KVM_REG_MIPS_CP0_CONFIG4        MIPS_CP0_32(16, 4)
> +#define KVM_REG_MIPS_CP0_CONFIG5        MIPS_CP0_32(16, 5)
>  #define KVM_REG_MIPS_CP0_ERROREPC       MIPS_CP0_64(30, 0)
>  
>  static inline int kvm_mips_put_one_reg(CPUState *cs, uint64_t reg_id,
> @@ -305,6 +311,34 @@ static inline int kvm_mips_get_one_reg64(CPUState *cs, uint64 reg_id,
>      return kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, &cp0reg);
>  }
>  
> +#define KVM_REG_MIPS_CP0_CONFIG_MASK    (1 << CP0C0_M)
> +#define KVM_REG_MIPS_CP0_CONFIG1_MASK   (1 << CP0C1_M)
> +#define KVM_REG_MIPS_CP0_CONFIG2_MASK   (1 << CP0C2_M)
> +#define KVM_REG_MIPS_CP0_CONFIG3_MASK   (1 << CP0C3_M)
> +#define KVM_REG_MIPS_CP0_CONFIG4_MASK   (1 << CP0C4_M)

CP0Cx_M is 31, thus without "U" suffix 1 is left shifted into sign bit
which is undefined behaviour.

> +#define KVM_REG_MIPS_CP0_CONFIG5_MASK   0
> +
> +static inline int kvm_mips_change_one_reg(CPUState *cs, uint64_t reg_id,
> +                                          int32_t *addr, int32_t mask)
> +{
> +    int err;
> +    int32_t tmp, change;
> +
> +    err = kvm_mips_get_one_reg(cs, reg_id, &tmp);
> +    if (err < 0) {
> +        return err;
> +    }
> +
> +    /* only change bits in mask */
> +    change = (*addr ^ tmp) & mask;
> +    if (!change) {
> +        return 0;
> +    }
> +
> +    tmp = tmp ^ change;
> +    return kvm_mips_put_one_reg(cs, reg_id, &tmp);
> +}
> +
>  /*
>   * We freeze the KVM timer when either the VM clock is stopped or the state is
>   * saved (the state is dirty).
> @@ -527,6 +561,48 @@ static int kvm_mips_put_cp0_registers(CPUState *cs, int level)
>          DPRINTF("%s: Failed to put CP0_PRID (%d)\n", __func__, err);
>          ret = err;
>      }
> +    err = kvm_mips_change_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG,
> +                                  &env->CP0_Config0,
> +                                  KVM_REG_MIPS_CP0_CONFIG_MASK);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to change CP0_CONFIG (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_change_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG1,
> +                                  &env->CP0_Config1,
> +                                  KVM_REG_MIPS_CP0_CONFIG1_MASK);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to change CP0_CONFIG1 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_change_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG2,
> +                                  &env->CP0_Config2,
> +                                  KVM_REG_MIPS_CP0_CONFIG2_MASK);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to change CP0_CONFIG2 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_change_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG3,
> +                                  &env->CP0_Config3,
> +                                  KVM_REG_MIPS_CP0_CONFIG3_MASK);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to change CP0_CONFIG3 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_change_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG4,
> +                                  &env->CP0_Config4,
> +                                  KVM_REG_MIPS_CP0_CONFIG4_MASK);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to change CP0_CONFIG4 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_change_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG5,
> +                                  &env->CP0_Config5,
> +                                  KVM_REG_MIPS_CP0_CONFIG5_MASK);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to change CP0_CONFIG5 (%d)\n", __func__, err);
> +        ret = err;
> +    }
>      err = kvm_mips_put_one_ulreg(cs, KVM_REG_MIPS_CP0_ERROREPC,
>                                   &env->CP0_ErrorEPC);
>      if (err < 0) {
> @@ -618,6 +694,38 @@ static int kvm_mips_get_cp0_registers(CPUState *cs)
>          DPRINTF("%s: Failed to get CP0_PRID (%d)\n", __func__, err);
>          ret = err;
>      }
> +    err = kvm_mips_get_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG, &env->CP0_Config0);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to get CP0_CONFIG (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_get_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG1, &env->CP0_Config1);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to get CP0_CONFIG1 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_get_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG2, &env->CP0_Config2);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to get CP0_CONFIG2 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_get_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG3, &env->CP0_Config3);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to get CP0_CONFIG3 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_get_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG4,
> +                               &env->CP0_Config4);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to get CP0_CONFIG4 (%d)\n", __func__, err);
> +        ret = err;
> +    }
> +    err = kvm_mips_get_one_reg(cs, KVM_REG_MIPS_CP0_CONFIG5,
> +                               &env->CP0_Config5);
> +    if (err < 0) {
> +        DPRINTF("%s: Failed to get CP0_CONFIG5 (%d)\n", __func__, err);
> +        ret = err;
> +    }

There's a minor style inconsistency here - for Config4 and Config5 the
last argument has been moved to a new line whereas for Config{0,1,2,3}
all arguments are in the same line.

>      err = kvm_mips_get_one_ulreg(cs, KVM_REG_MIPS_CP0_ERROREPC,
>                                   &env->CP0_ErrorEPC);
>      if (err < 0) {
>