Date:   Thu, 9 Mar 2023 16:22:37 -0800
From:   David Matlack <dmatlack@google.com>
To:     Vipin Sharma <vipinsh@google.com>
Cc:     seanjc@google.com, pbonzini@redhat.com, bgardon@google.com,
        jmattson@google.com, mizhang@google.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [Patch v4 03/18] KVM: x86/mmu: Track count of pages in KVM MMU
 page caches globally
Message-ID: <ZAp4Tb8MYoggn/Rb@google.com>
References: <20230306224127.1689967-1-vipinsh@google.com>
 <20230306224127.1689967-4-vipinsh@google.com>
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On Mon, Mar 06, 2023 at 02:41:12PM -0800, Vipin Sharma wrote:
>
>  static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
>  {
>  	kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache);
> -	kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
> +	mutex_lock(&vcpu->arch.mmu_shadow_page_cache_lock);
> +	mmu_free_sp_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
> +	mutex_unlock(&vcpu->arch.mmu_shadow_page_cache_lock);

Is this lock necessary (even when the shrinker is hooked up)?
mmu_free_memory_caches() is only called when KVM fails to create a vCPU
(before it has been added to vcpu_array) or during VM destruction (after
the VM has been removed from vm_list).