linux-kernel - Re: [PATCH v2 07/11] KVM: x86/MMU: Factor out updating NX hugepages state for a VM

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Message-ID: <YkIYF6HzLy+l6tu8@google.com>
Date:   Mon, 28 Mar 2022 20:18:31 +0000
From:   David Matlack <dmatlack@...gle.com>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        David Dunn <daviddunn@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Junaid Shahid <junaids@...gle.com>
Subject: Re: [PATCH v2 07/11] KVM: x86/MMU: Factor out updating NX hugepages
 state for a VM

On Mon, Mar 21, 2022 at 04:48:40PM -0700, Ben Gardon wrote:
> Factor out the code to update the NX hugepages state for an individual
> VM. This will be expanded in future commits to allow per-VM control of
> Nx hugepages.
> 
> No functional change intended.
> 
> Signed-off-by: Ben Gardon <bgardon@...gle.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 3b8da8b0745e..1b59b56642f1 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6195,6 +6195,15 @@ static void __set_nx_huge_pages(bool val)
>  	nx_huge_pages = itlb_multihit_kvm_mitigation = val;
>  }
>  
> +static int kvm_update_nx_huge_pages(struct kvm *kvm)
> +{
> +	mutex_lock(&kvm->slots_lock);
> +	kvm_mmu_zap_all_fast(kvm);
> +	mutex_unlock(&kvm->slots_lock);
> +
> +	wake_up_process(kvm->arch.nx_lpage_recovery_thread);
> +}
> +
>  static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
>  {
>  	bool old_val = nx_huge_pages;
> @@ -6217,13 +6226,8 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
>  
>  		mutex_lock(&kvm_lock);
>  

nit: This blank line is asymmetrical with mutex_unlock().

> -		list_for_each_entry(kvm, &vm_list, vm_list) {
> -			mutex_lock(&kvm->slots_lock);
> -			kvm_mmu_zap_all_fast(kvm);
> -			mutex_unlock(&kvm->slots_lock);
> -
> -			wake_up_process(kvm->arch.nx_lpage_recovery_thread);
> -		}
> +		list_for_each_entry(kvm, &vm_list, vm_list)
> +			kvm_set_nx_huge_pages(kvm);

This should be kvm_update_nx_huge_pages() right?

>  		mutex_unlock(&kvm_lock);
>  	}
>  
> -- 
> 2.35.1.894.gb6a874cedc-goog
>