Re: [PATCH v2 12/50] KVM: VMX: Move Hyper-V eVMCS initialization to helper

From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, "David Hildenbrand" <david@redhat.com>,
	"Atish Patra" <atishp@atishpatra.org>,
	linux-kernel@vger.kernel.org, "Kai Huang" <kai.huang@intel.com>,
	linux-riscv@lists.infradead.org,
	"Claudio Imbrenda" <imbrenda@linux.ibm.com>,
	kvmarm@lists.cs.columbia.edu, linux-s390@vger.kernel.org,
	"Janosch Frank" <frankja@linux.ibm.com>,
	"Huacai Chen" <chenhuacai@kernel.org>,
	"Aleksandar Markovic" <aleksandar.qemu.devel@gmail.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Christian Borntraeger" <borntraeger@linux.ibm.com>,
	"David Woodhouse" <dwmw2@infradead.org>,
	"Matthew Rosato" <mjrosato@linux.ibm.com>,
	"Chao Gao" <chao.gao@intel.com>,
	"Eric Farman" <farman@linux.ibm.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	"Sean Christopherson" <seanjc@google.com>,
	"Paul Durrant" <paul@xen.org>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Yuan Yao" <yuan.yao@intel.com>,
	kvmarm@lists.linux.dev, "Thomas Gleixner" <tglx@linutronix.de>,
	"Alexandru Elisei" <alexandru.elisei@arm.com>
Subject: Re: [PATCH v2 12/50] KVM: VMX: Move Hyper-V eVMCS initialization to helper
Date: Thu, 01 Dec 2022 16:22:45 +0100	[thread overview]
Message-ID: <87k03bf8sa.fsf@ovpn-194-141.brq.redhat.com> (raw)
In-Reply-To: <20221130230934.1014142-13-seanjc@google.com>

Sean Christopherson <seanjc@google.com> writes:

> Move Hyper-V's eVMCS initialization to a dedicated helper to clean up
> vmx_init(), and add a comment to call out that the Hyper-V init code
> doesn't need to be unwound if vmx_init() ultimately fails.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 73 +++++++++++++++++++++++++-----------------
>  1 file changed, 43 insertions(+), 30 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index c0de7160700b..b8bf95b9710d 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -523,6 +523,8 @@ static inline void vmx_segment_cache_clear(struct vcpu_vmx *vmx)
>  static unsigned long host_idt_base;
>  
>  #if IS_ENABLED(CONFIG_HYPERV)
> +static struct kvm_x86_ops vmx_x86_ops __initdata;
> +
>  static bool __read_mostly enlightened_vmcs = true;
>  module_param(enlightened_vmcs, bool, 0444);
>  
> @@ -551,6 +553,43 @@ static int hv_enable_l2_tlb_flush(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> +static __init void hv_init_evmcs(void)
> +{
> +	int cpu;
> +
> +	if (!enlightened_vmcs)
> +		return;
> +
> +	/*
> +	 * Enlightened VMCS usage should be recommended and the host needs
> +	 * to support eVMCS v1 or above.
> +	 */
> +	if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED &&
> +	    (ms_hyperv.nested_features & HV_X64_ENLIGHTENED_VMCS_VERSION) >=
> +	     KVM_EVMCS_VERSION) {
> +
> +		/* Check that we have assist pages on all online CPUs */
> +		for_each_online_cpu(cpu) {
> +			if (!hv_get_vp_assist_page(cpu)) {
> +				enlightened_vmcs = false;
> +				break;
> +			}
> +		}
> +
> +		if (enlightened_vmcs) {
> +			pr_info("KVM: vmx: using Hyper-V Enlightened VMCS\n");
> +			static_branch_enable(&enable_evmcs);
> +		}
> +
> +		if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH)
> +			vmx_x86_ops.enable_l2_tlb_flush
> +				= hv_enable_l2_tlb_flush;
> +
> +	} else {
> +		enlightened_vmcs = false;
> +	}
> +}
> +
>  static void hv_reset_evmcs(void)
>  {
>  	struct hv_vp_assist_page *vp_ap;
> @@ -577,6 +616,7 @@ static void hv_reset_evmcs(void)
>  }
>  
>  #else /* IS_ENABLED(CONFIG_HYPERV) */
> +static void hv_init_evmcs(void) {}
>  static void hv_reset_evmcs(void) {}
>  #endif /* IS_ENABLED(CONFIG_HYPERV) */
>  
> @@ -8500,38 +8540,11 @@ static int __init vmx_init(void)
>  {
>  	int r, cpu;
>  
> -#if IS_ENABLED(CONFIG_HYPERV)
>  	/*
> -	 * Enlightened VMCS usage should be recommended and the host needs
> -	 * to support eVMCS v1 or above. We can also disable eVMCS support
> -	 * with module parameter.
> +	 * Note, hv_init_evmcs() touches only VMX knobs, i.e. there's nothing
> +	 * to unwind if a later step fails.
>  	 */
> -	if (enlightened_vmcs &&
> -	    ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED &&
> -	    (ms_hyperv.nested_features & HV_X64_ENLIGHTENED_VMCS_VERSION) >=
> -	    KVM_EVMCS_VERSION) {
> -
> -		/* Check that we have assist pages on all online CPUs */
> -		for_each_online_cpu(cpu) {
> -			if (!hv_get_vp_assist_page(cpu)) {
> -				enlightened_vmcs = false;
> -				break;
> -			}
> -		}
> -
> -		if (enlightened_vmcs) {
> -			pr_info("KVM: vmx: using Hyper-V Enlightened VMCS\n");
> -			static_branch_enable(&enable_evmcs);
> -		}
> -
> -		if (ms_hyperv.nested_features & HV_X64_NESTED_DIRECT_FLUSH)
> -			vmx_x86_ops.enable_l2_tlb_flush
> -				= hv_enable_l2_tlb_flush;
> -
> -	} else {
> -		enlightened_vmcs = false;
> -	}
> -#endif
> +	hv_init_evmcs();
>  
>  	r = kvm_init(&vmx_init_ops, sizeof(struct vcpu_vmx),
>  		     __alignof__(struct vcpu_vmx), THIS_MODULE);

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

-- 
Vitaly