linux-kernel - Re: [PATCH v2 Resend 3/3] KVM: MIPS: Support kvm modules autoprobed when startup system

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Date:   Fri, 13 Mar 2020 14:38:20 +0800
From:   Huacai Chen <chenhc@...ote.com>
To:     Xing Li <lixing@...ngson.cn>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "open list:MIPS" <linux-mips@...r.kernel.org>, kvm@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, maobibo@...ngson.cn,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: Re: [PATCH v2 Resend 3/3] KVM: MIPS: Support kvm modules autoprobed
 when startup system

Hi, Lixing,

On Fri, Mar 13, 2020 at 11:14 AM Xing Li <lixing@...ngson.cn> wrote:
>
> Currently, the module_init of kvm_mips_init cannot force the kvm
> modules insmod when startup system.
>
> Add new feature CPU_MIPS_VZ in elf_hwcap to support KVM auto probe
> when hardware virtualization supported.
I think this patch is not suitable, because:
1, KVM has VZ mode and TE mode, you only consider VZ mode?
2, As X86 does, you can use udev or modprobe.conf to autoprobe kvm module.

Regards,
Huacai
>
> Signed-off-by: Xing Li <lixing@...ngson.cn>
> ---
>  arch/mips/include/uapi/asm/hwcap.h | 1 +
>  arch/mips/kernel/cpu-probe.c       | 4 +++-
>  arch/mips/kvm/mips.c               | 3 ++-
>  3 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/include/uapi/asm/hwcap.h b/arch/mips/include/uapi/asm/hwcap.h
> index 1ade1da..9e66509 100644
> --- a/arch/mips/include/uapi/asm/hwcap.h
> +++ b/arch/mips/include/uapi/asm/hwcap.h
> @@ -17,5 +17,6 @@
>  #define HWCAP_LOONGSON_MMI  (1 << 11)
>  #define HWCAP_LOONGSON_EXT  (1 << 12)
>  #define HWCAP_LOONGSON_EXT2 (1 << 13)
> +#define HWCAP_MIPS_VZ       (1 << 14)
>
>  #endif /* _UAPI_ASM_HWCAP_H */
> diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
> index c543326..b305269 100644
> --- a/arch/mips/kernel/cpu-probe.c
> +++ b/arch/mips/kernel/cpu-probe.c
> @@ -2242,8 +2242,10 @@ void cpu_probe(void)
>         if (cpu_has_loongson_ext2)
>                 elf_hwcap |= HWCAP_LOONGSON_EXT2;
>
> -       if (cpu_has_vz)
> +       if (cpu_has_vz) {
>                 cpu_probe_vz(c);
> +               elf_hwcap |= HWCAP_MIPS_VZ;
> +       }
>
>         cpu_probe_vmbits(c);
>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 1109924..1da5df3 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -19,6 +19,7 @@
>  #include <linux/sched/signal.h>
>  #include <linux/fs.h>
>  #include <linux/memblock.h>
> +#include <linux/cpufeature.h>
>
>  #include <asm/fpu.h>
>  #include <asm/page.h>
> @@ -1742,7 +1743,7 @@ static void __exit kvm_mips_exit(void)
>         unregister_die_notifier(&kvm_mips_csr_die_notifier);
>  }
>
> -module_init(kvm_mips_init);
> +module_cpu_feature_match(MIPS_VZ, kvm_mips_init);
>  module_exit(kvm_mips_exit);
>
>  EXPORT_TRACEPOINT_SYMBOL(kvm_exit);
> --
> 2.1.0
>