linux-kernel - Re: [PATCH 5/6] kvm: allocate vcpu pointer array separately

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Message-ID: <001b7eab-ed7b-da27-a623-057781cf1211@redhat.com>
Date:   Mon, 26 Jul 2021 15:40:19 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        kvm@...r.kernel.org
Cc:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH 5/6] kvm: allocate vcpu pointer array separately

On 01/07/21 17:41, Juergen Gross wrote:
>   {
> -	if (!has_vhe())
> +	if (!has_vhe()) {
> +		kfree(kvm->vcpus);
>   		kfree(kvm);
> -	else
> +	} else {
> +		vfree(kvm->vcpus);
>   		vfree(kvm);
> +	}
>   }
>   
>   int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 79138c91f83d..39cbc4b6bffb 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1440,10 +1440,7 @@ static inline void kvm_ops_static_call_update(void)
>   }
>   
>   #define __KVM_HAVE_ARCH_VM_ALLOC
> -static inline struct kvm *kvm_arch_alloc_vm(void)
> -{
> -	return __vmalloc(kvm_x86_ops.vm_size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
> -}
> +struct kvm *kvm_arch_alloc_vm(void);
>   void kvm_arch_free_vm(struct kvm *kvm);
>   
>   #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLB
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3af398ef1fc9..a9b0bb2221ea 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10741,9 +10741,28 @@ void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
>   	static_call(kvm_x86_sched_in)(vcpu, cpu);
>   }
>   
> +struct kvm *kvm_arch_alloc_vm(void)
> +{
> +	struct kvm *kvm;
> +
> +	kvm = __vmalloc(kvm_x86_ops.vm_size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
> +	if (!kvm)
> +		return NULL;
> +
> +	kvm->vcpus = __vmalloc(KVM_MAX_VCPUS * sizeof(void *),
> +			       GFP_KERNEL_ACCOUNT | __GFP_ZERO);
> +	if (!kvm->vcpus) {
> +		vfree(kvm);
> +		kvm = NULL;
> +	}
> +

Let's keep this cleaner:

1) use kvfree in the common version of kvm_arch_free_vm

2) split __KVM_HAVE_ARCH_VM_ALLOC and __KVM_HAVE_ARCH_VM_FREE (ARM does 
not need it once kvfree is used)

3) define a __kvm_arch_free_vm version that is defined even if 
!__KVM_HAVE_ARCH_VM_FREE, and which can be used on x86.

Paolo