linux-kernel - Re: [PATCH 12/12] KVM: x86: do not unload MMU roots on all role changes

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Message-ID: <9871bfc0-42e8-c485-687f-dd111224fbe6@amd.com>
Date:   Fri, 11 Feb 2022 14:38:48 +0530
From:   "Nikunj A. Dadhania" <nikunj@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     vkuznets@...hat.com, mlevitsk@...hat.com, dmatlack@...gle.com,
        seanjc@...gle.com
Subject: Re: [PATCH 12/12] KVM: x86: do not unload MMU roots on all role
 changes

On 2/9/2022 10:30 PM, Paolo Bonzini wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0d3646535cc5..97c4f5fc291f 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -873,8 +873,12 @@ void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned lon
>  		kvm_async_pf_hash_reset(vcpu);
>  	}
>  
> -	if ((cr0 ^ old_cr0) & KVM_MMU_CR0_ROLE_BITS)
> +	if ((cr0 ^ old_cr0) & KVM_MMU_CR0_ROLE_BITS) {
> +		/* Flush the TLB if CR0 is changed 1 -> 0.  */

                                      ^^ CR0.PG here ?

> +		if ((old_cr0 & X86_CR0_PG) && !(cr0 & X86_CR0_PG))
> +			kvm_mmu_unload(vcpu);
>  		kvm_mmu_reset_context(vcpu);
> +	}

Regards
Nikunj