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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Sean Christopherson <seanjc@google.com>
Cc:     James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Oliver Upton <oliver.upton@linux.dev>,
        Atish Patra <atishp@atishpatra.org>,
        David Hildenbrand <david@redhat.com>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org,
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        Paolo Bonzini <pbonzini@redhat.com>,
        Marc Zyngier <maz@kernel.org>,
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        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Eric Farman <farman@linux.ibm.com>,
        Sean Christopherson <seanjc@google.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Paul Durrant <paul@xen.org>
Subject: Re: [PATCH v2 12/50] KVM: VMX: Move Hyper-V eVMCS initialization to
 helper
In-Reply-To: <20221130230934.1014142-13-seanjc@google.com>
References: <20221130230934.1014142-1-seanjc@google.com>
 <20221130230934.1014142-13-seanjc@google.com>
Date:   Thu, 01 Dec 2022 16:22:45 +0100
Message-ID: <87k03bf8sa.fsf@ovpn-194-141.brq.redhat.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

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