Re: [PATCH v19 022/130] KVM: x86/vmx: Refactor KVM VMX module init/exit functions

Yin, Fengwei
2024-03-11T05:32:22Z

On 2/26/2024 4:25 PM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Currently, KVM VMX module initialization/exit functions are a single
> function each. Refactor KVM VMX module initialization functions into KVM
> common part and VMX part so that TDX specific part can be added cleanly.
> Opportunistically refactor module exit function as well.
>
> The current module initialization flow is,
> 0.) Check if VMX is supported,
> 1.) hyper-v specific initialization,
> 2.) system-wide x86 specific and vendor specific initialization,
> 3.) Final VMX specific system-wide initialization,
> 4.) calculate the sizes of VMX kvm structure and VMX vcpu structure,
> 5.) report those sizes to the KVM common layer and KVM common
> initialization
>
> Refactor the KVM VMX module initialization function into functions with a
> wrapper function to separate VMX logic in vmx.c from a file, main.c, common
> among VMX and TDX. Introduce a wrapper function for vmx_init().
>
> The KVM architecture common layer allocates struct kvm with reported size
> for architecture-specific code. The KVM VMX module defines its structure
> as struct vmx_kvm { struct kvm; VMX specific members;} and uses it as
> struct vmx kvm. Similar for vcpu structure. TDX KVM patches will define
> TDX specific kvm and vcpu structures.
>
> The current module exit function is also a single function, a combination
> of VMX specific logic and common KVM logic. Refactor it into VMX specific
> logic and KVM common logic. This is just refactoring to keep the VMX
> specific logic in vmx.c from main.c.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> v19:
> - Eliminate the unnecessary churn with vmx_hardware_setup() by Xiaoyao
>
> v18:
> - Move loaded_vmcss_on_cpu initialization to vt_init() before
> kvm_x86_vendor_init().
> - added __init to an empty stub fucntion, hv_init_evmcs().
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>

With one minor comment. See below.

> ---
> arch/x86/kvm/vmx/main.c | 54 ++++++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.c | 60 +++++---------------------------------
> arch/x86/kvm/vmx/x86_ops.h | 14 +++++++++
> 3 files changed, 75 insertions(+), 53 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index eeb7a43b271d..18cecf12c7c8 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -167,3 +167,57 @@ struct kvm_x86_init_ops vt_init_ops __initdata = {
> .runtime_ops = &vt_x86_ops,
> .pmu_ops = &intel_pmu_ops,
> };
> +
> +static int __init vt_init(void)
> +{
> + unsigned int vcpu_size, vcpu_align;
> + int cpu, r;
> +
> + if (!kvm_is_vmx_supported())
> + return -EOPNOTSUPP;
> +
> + /*
> + * Note, hv_init_evmcs() touches only VMX knobs, i.e. there's nothing
> + * to unwind if a later step fails.
> + */
> + 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;
> +
> + /*
> + * Common KVM initialization _must_ come last, after this, /dev/kvm is
> + * exposed to userspace!
> + */
> + vcpu_size = sizeof(struct vcpu_vmx);
> + vcpu_align = __alignof__(struct vcpu_vmx);
> + r = kvm_init(vcpu_size, vcpu_align, THIS_MODULE);
> + if (r)
> + goto err_kvm_init;
> +
> + return 0;
> +
> +err_kvm_init:
> + vmx_exit();
> +err_vmx_init:
> + kvm_x86_vendor_exit();
> + return r;
> +}
> +module_init(vt_init);
> +
> +static void vt_exit(void)
> +{
> + kvm_exit();
> + kvm_x86_vendor_exit();
> + vmx_exit();
> +}
> +module_exit(vt_exit);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 8af0668e4dca..2fb1cd2e28a2 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.
> */
> -static DEFINE_PER_CPU(struct list_head, loaded_vmcss_on_cpu);
> +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);
> @@ -537,7 +537,7 @@ static int hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> -static __init void hv_init_evmcs(void)
> +__init void hv_init_evmcs(void)
> {
> int cpu;
>
> @@ -573,7 +573,7 @@ static __init void hv_init_evmcs(void)
> }
> }
>
> -static void hv_reset_evmcs(void)
> +void hv_reset_evmcs(void)
> {
> struct hv_vp_assist_page *vp_ap;
>
> @@ -597,10 +597,6 @@ static void hv_reset_evmcs(void)
> vp_ap->current_nested_vmcs = 0;
> vp_ap->enlighten_vmentry = 0;
> }
> -
> -#else /* IS_ENABLED(CONFIG_HYPERV) */
> -static void hv_init_evmcs(void) {}
> -static void hv_reset_evmcs(void) {}
> #endif /* IS_ENABLED(CONFIG_HYPERV) */
>
> /*
> @@ -2743,7 +2739,7 @@ static bool __kvm_is_vmx_supported(void)
> return true;
> }
>
> -static bool kvm_is_vmx_supported(void)
> +bool kvm_is_vmx_supported(void)
> {
> bool supported;
>
> @@ -8508,7 +8504,7 @@ static void vmx_cleanup_l1d_flush(void)
> l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
> }
>
> -static void __vmx_exit(void)
> +void vmx_exit(void)
> {
> allow_smaller_maxphyaddr = false;
>
> @@ -8517,36 +8513,10 @@ static void __vmx_exit(void)
> vmx_cleanup_l1d_flush();
> }
>
> -static void vmx_exit(void)
> -{
> - kvm_exit();
> - kvm_x86_vendor_exit();
> -
> - __vmx_exit();
> -}
> -module_exit(vmx_exit);
> -
> -static int __init vmx_init(void)
> +int __init vmx_init(void)
> {
> int r, cpu;
>
> - if (!kvm_is_vmx_supported())
> - return -EOPNOTSUPP;
> -
> - /*
> - * Note, hv_init_evmcs() touches only VMX knobs, i.e. there's nothing
> - * to unwind if a later step fails.
> - */
> - 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;
> -
> /*
> * Must be called after common x86 init so enable_ept is properly set
> * up. Hand the parameter mitigation value in which was stored in
I am wondering whether the first sentence of above comment should be
moved to vt_init()? So vt_init() has whole information about the init
sequence.

Regards
Yin, Fengwei

> @@ -8556,7 +8526,7 @@ static int __init vmx_init(void)
> */
> r = vmx_setup_l1d_flush(vmentry_l1d_flush_param);
> if (r)
> - goto err_l1d_flush;
> + return r;
>
> for_each_possible_cpu(cpu)
> pi_init_cpu(cpu);
> @@ -8573,21 +8543,5 @@ static int __init vmx_init(void)
> if (!enable_ept)
> allow_smaller_maxphyaddr = true;
>
> - /*
> - * Common KVM initialization _must_ come last, after this, /dev/kvm is
> - * exposed to userspace!
> - */
> - r = kvm_init(sizeof(struct vcpu_vmx), __alignof__(struct vcpu_vmx),
> - THIS_MODULE);
> - if (r)
> - goto err_kvm_init;
> -
> return 0;
> -
> -err_kvm_init:
> - __vmx_exit();
> -err_l1d_flush:
> - kvm_x86_vendor_exit();
> - return r;
> }
> -module_init(vmx_init);
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 2f8b6c43fe0f..b936388853ab 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -6,6 +6,20 @@
>
> #include "x86.h"
>
> +#if IS_ENABLED(CONFIG_HYPERV)
> +__init void hv_init_evmcs(void);
> +void hv_reset_evmcs(void);
> +#else /* IS_ENABLED(CONFIG_HYPERV) */
> +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);
> +
> extern struct kvm_x86_ops vt_x86_ops __initdata;
> extern struct kvm_x86_init_ops vt_init_ops __initdata;
>