linux-kernel - Re: [PATCH v7 043/102] KVM: x86/mmu: Focibly use TDP MMU for TDX

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Date:   Mon, 11 Jul 2022 13:48:44 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     isaku.yamahata@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v7 043/102] KVM: x86/mmu: Focibly use TDP MMU for TDX

On Mon, Jun 27, 2022 at 02:53:35PM -0700, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> In this patch series, TDX supports only TDP MMU and doesn't support legacy
> MMU.  Forcibly use TDP MMU for TDX irrelevant of kernel parameter to
> disable TDP MMU.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 82f1bfac7ee6..7eb41b176d1e 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -18,8 +18,13 @@ int kvm_mmu_init_tdp_mmu(struct kvm *kvm)
>  {
>  	struct workqueue_struct *wq;
>
> -	if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled))
> -		return 0;
> +	/*
> +	 *  Because TDX supports only TDP MMU, forcibly use TDP MMU in the case
> +	 *  of TDX.
> +	 */
> +	if (kvm->arch.vm_type != KVM_X86_TDX_VM &&
> +		(!tdp_enabled || !READ_ONCE(tdp_mmu_enabled)))
> +		return false;

Please return 0 here for int return value type.

>
>  	wq = alloc_workqueue("kvm", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 0);
>  	if (!wq)
> --
> 2.25.1
>