linux-kernel - Re: [PATCH 13/21] KVM: TDX: Handle TLB tracking for TDX

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Message-ID: <e4ebdfca-fcb8-43fb-a15b-591d083b286f@redhat.com>
Date: Tue, 10 Sep 2024 10:16:27 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>, seanjc@...gle.com,
 kvm@...r.kernel.org
Cc: kai.huang@...el.com, dmatlack@...gle.com, isaku.yamahata@...il.com,
 yan.y.zhao@...el.com, nik.borisov@...e.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/21] KVM: TDX: Handle TLB tracking for TDX

On 9/4/24 05:07, Rick Edgecombe wrote:
> +static void vt_flush_tlb_all(struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * TDX calls tdx_track() in tdx_sept_remove_private_spte() to ensure
> +	 * private EPT will be flushed on the next TD enter.
> +	 * No need to call tdx_track() here again even when this callback is as
> +	 * a result of zapping private EPT.
> +	 * Just invoke invept() directly here to work for both shared EPT and
> +	 * private EPT.
> +	 */
> +	if (is_td_vcpu(vcpu)) {
> +		ept_sync_global();
> +		return;
> +	}
> +
> +	vmx_flush_tlb_all(vcpu);
> +}
> +
> +static void vt_flush_tlb_current(struct kvm_vcpu *vcpu)
> +{
> +	if (is_td_vcpu(vcpu)) {
> +		tdx_flush_tlb_current(vcpu);
> +		return;
> +	}
> +
> +	vmx_flush_tlb_current(vcpu);
> +}
> +

I'd do it slightly different:

static void vt_flush_tlb_all(struct kvm_vcpu *vcpu)
{
	if (is_td_vcpu(vcpu)) {
		tdx_flush_tlb_all(vcpu);
		return;
	}

	vmx_flush_tlb_all(vcpu);
}

static void vt_flush_tlb_current(struct kvm_vcpu *vcpu)
{
	if (is_td_vcpu(vcpu)) {
		/*
		 * flush_tlb_current() is used only the first time for
		 * the vcpu runs, since TDX supports neither shadow
		 * nested paging nor SMM.  Keep this function simple.
		 */
		tdx_flush_tlb_all(vcpu);
		return;
	}

	vmx_flush_tlb_current(vcpu);
}

and put the implementation details close to tdx_track:

void tdx_flush_tlb_all(struct kvm_vcpu *vcpu)
{
	/*
	 * TDX calls tdx_track() in tdx_sept_remove_private_spte() to
	 * ensure private EPT will be flushed on the next TD enter.
	 * No need to call tdx_track() here again, even when this
	 * callback is a result of zapping private EPT.  Just
	 * invoke invept() directly here, which works for both shared
	 * EPT and private EPT.
	 */
	ept_sync_global();
}