linux-kernel - Re: [PATCH v3 4/4] LoongArch: KVM: Add VM LBT feature detection support

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Message-ID: <CAAhV-H7wdMH=fdGhtxcJ9zY+H-PKT2q0rgrsEPm+LhBgCqNsjQ@mail.gmail.com>
Date: Sun, 23 Jun 2024 18:14:19 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>, kvm@...r.kernel.org, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] LoongArch: KVM: Add VM LBT feature detection support

Hi, Bibo,

On Mon, May 27, 2024 at 3:46 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>
> Before virt machine or vcpu is created, vmm need check supported
> features from KVM. Here ioctl command KVM_HAS_DEVICE_ATTR is added
> for VM, and macro KVM_LOONGARCH_VM_FEAT_CTRL is added to check
> supported feature.
>
> Three sub-features relative with LBT are added, in later any new
> feature can be added if it is used for vmm. The sub-features is
>  KVM_LOONGARCH_VM_FEAT_X86BT
>  KVM_LOONGARCH_VM_FEAT_ARMBT
>  KVM_LOONGARCH_VM_FEAT_MIPSBT
>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
>  arch/loongarch/include/uapi/asm/kvm.h |  6 ++++
>  arch/loongarch/kvm/vm.c               | 44 ++++++++++++++++++++++++++-
>  2 files changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
> index 656aa6a723a6..ed12e509815c 100644
> --- a/arch/loongarch/include/uapi/asm/kvm.h
> +++ b/arch/loongarch/include/uapi/asm/kvm.h
> @@ -91,6 +91,12 @@ struct kvm_fpu {
>  #define KVM_IOC_CSRID(REG)             LOONGARCH_REG_64(KVM_REG_LOONGARCH_CSR, REG)
>  #define KVM_IOC_CPUCFG(REG)            LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG, REG)
>
> +/* Device Control API on vm fd */
> +#define KVM_LOONGARCH_VM_FEAT_CTRL     0
> +#define  KVM_LOONGARCH_VM_FEAT_X86BT   0
> +#define  KVM_LOONGARCH_VM_FEAT_ARMBT   1
> +#define  KVM_LOONGARCH_VM_FEAT_MIPSBT  2
I think LBT should be vcpu features rather than vm features, which is
the same like CPUCFG and FP/SIMD.

Moreover, this patch can be merged to the 2nd one.

Huacai

> +
>  /* Device Control API on vcpu fd */
>  #define KVM_LOONGARCH_VCPU_CPUCFG      0
>  #define KVM_LOONGARCH_VCPU_PVTIME_CTRL 1
> diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
> index 6b2e4f66ad26..09e05108c68b 100644
> --- a/arch/loongarch/kvm/vm.c
> +++ b/arch/loongarch/kvm/vm.c
> @@ -99,7 +99,49 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>         return r;
>  }
>
> +static int kvm_vm_feature_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> +       switch (attr->attr) {
> +       case KVM_LOONGARCH_VM_FEAT_X86BT:
> +               if (cpu_has_lbt_x86)
> +                       return 0;
> +               return -ENXIO;
> +       case KVM_LOONGARCH_VM_FEAT_ARMBT:
> +               if (cpu_has_lbt_arm)
> +                       return 0;
> +               return -ENXIO;
> +       case KVM_LOONGARCH_VM_FEAT_MIPSBT:
> +               if (cpu_has_lbt_mips)
> +                       return 0;
> +               return -ENXIO;
> +       default:
> +               return -ENXIO;
> +       }
> +}
> +
> +static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
> +{
> +       switch (attr->group) {
> +       case KVM_LOONGARCH_VM_FEAT_CTRL:
> +               return kvm_vm_feature_has_attr(kvm, attr);
> +       default:
> +               return -ENXIO;
> +       }
> +}
> +
>  int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
>  {
> -       return -ENOIOCTLCMD;
> +       struct kvm *kvm = filp->private_data;
> +       void __user *argp = (void __user *)arg;
> +       struct kvm_device_attr attr;
> +
> +       switch (ioctl) {
> +       case KVM_HAS_DEVICE_ATTR:
> +               if (copy_from_user(&attr, argp, sizeof(attr)))
> +                       return -EFAULT;
> +
> +               return kvm_vm_has_attr(kvm, &attr);
> +       default:
> +               return -EINVAL;
> +       }
>  }
> --
> 2.39.3
>