linux-kernel - Re: [PATCH v18 007/121] KVM: VMX: Reorder vmx initialization with kvm vendor initialization

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Message-ID: <20240129085647.o3vm6mglo2htfy2n@yy-desk-7060>
Date: Mon, 29 Jan 2024 16:56:47 +0800
From: Yuan Yao <yuan.yao@...ux.intel.com>
To: isaku.yamahata@...el.com
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
	erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
	Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
	chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com
Subject: Re: [PATCH v18 007/121] KVM: VMX: Reorder vmx initialization with
 kvm vendor initialization

On Mon, Jan 22, 2024 at 03:52:43PM -0800, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> To match vmx_exit cleanup.  Now vmx_init() is before kvm_x86_vendor_init(),
> vmx_init() can initialize loaded_vmcss_on_cpu.  Oppertunistically move it
> back into vmx_init().
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
> v18:
> - move the loaded_vmcss_on_cpu initialization to vmx_init().
> - fix error path of vt_init(). by Chao and Binbin
> ---
>  arch/x86/kvm/vmx/main.c    | 17 +++++++----------
>  arch/x86/kvm/vmx/vmx.c     |  6 ++++--
>  arch/x86/kvm/vmx/x86_ops.h |  2 --
>  3 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 18cecf12c7c8..443db8ec5cd5 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -171,7 +171,7 @@ struct kvm_x86_init_ops vt_init_ops __initdata = {
>  static int __init vt_init(void)
>  {
>  	unsigned int vcpu_size, vcpu_align;
> -	int cpu, r;
> +	int r;
>
>  	if (!kvm_is_vmx_supported())
>  		return -EOPNOTSUPP;
> @@ -182,18 +182,14 @@ static int __init vt_init(void)
>  	 */
>  	hv_init_evmcs();
>
> -	/* vmx_hardware_disable() accesses loaded_vmcss_on_cpu. */
> -	for_each_possible_cpu(cpu)
> -		INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
> -
> -	r = kvm_x86_vendor_init(&vt_init_ops);
> -	if (r)
> -		return r;
> -
>  	r = vmx_init();
>  	if (r)
>  		goto err_vmx_init;
>
> +	r = kvm_x86_vendor_init(&vt_init_ops);

Do kvm_x86_vendor_init() *after* vmx_init() leads to
"enable_ept" is used before set to 0 in some cases.

vmx_init() depends on "enable_ept" variable for below 2:
    vmx_setup_l1d_flush()
    allow_smaller_maxphyaddr = true;

And "enable_ept" can be set to 0 in:
kvm_x86_vendor_init()
    vmx_hardware_setup()

> +	if (r)
> +		goto err_vendor_init;
> +
>  	/*
>  	 * Common KVM initialization _must_ come last, after this, /dev/kvm is
>  	 * exposed to userspace!
> @@ -207,9 +203,10 @@ static int __init vt_init(void)
>  	return 0;
>
>  err_kvm_init:
> +	kvm_x86_vendor_exit();
> +err_vendor_init:
>  	vmx_exit();
>  err_vmx_init:
> -	kvm_x86_vendor_exit();
>  	return r;
>  }
>  module_init(vt_init);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 8efb956591d5..3f4dad3acb13 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -477,7 +477,7 @@ DEFINE_PER_CPU(struct vmcs *, current_vmcs);
>   * We maintain a per-CPU linked-list of VMCS loaded on that CPU. This is needed
>   * when a CPU is brought down, and we need to VMCLEAR all VMCSs loaded on it.
>   */
> -DEFINE_PER_CPU(struct list_head, loaded_vmcss_on_cpu);
> +static DEFINE_PER_CPU(struct list_head, loaded_vmcss_on_cpu);
>
>  static DECLARE_BITMAP(vmx_vpid_bitmap, VMX_NR_VPIDS);
>  static DEFINE_SPINLOCK(vmx_vpid_lock);
> @@ -8528,8 +8528,10 @@ int __init vmx_init(void)
>  	if (r)
>  		return r;
>
> -	for_each_possible_cpu(cpu)
> +	for_each_possible_cpu(cpu) {
> +		INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
>  		pi_init_cpu(cpu);
> +	}
>
>  	cpu_emergency_register_virt_callback(vmx_emergency_disable);
>
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index b936388853ab..bca2d27b3dfd 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -14,8 +14,6 @@ static inline __init void hv_init_evmcs(void) {}
>  static inline void hv_reset_evmcs(void) {}
>  #endif /* IS_ENABLED(CONFIG_HYPERV) */
>
> -DECLARE_PER_CPU(struct list_head, loaded_vmcss_on_cpu);
> -
>  bool kvm_is_vmx_supported(void);
>  int __init vmx_init(void);
>  void vmx_exit(void);
> --
> 2.25.1
>
>