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

Isaku Yamahata
2024-03-12T02:15:26Z

On Mon, Mar 11, 2024 at 01:32:08PM +0800,
"Yin, Fengwei" <fengwei.yin@intel.com> wrote:

>
>
> 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.

If we do so, we should move the call of "vmx_setup_l1d_flush() to vt_init().
I hesitated to remove static of vmx_setup_l1d_flush().
--
Isaku Yamahata <isaku.yamahata@intel.com>