linux-kernel - Re: [PATCH v19 120/130] KVM: TDX: Add a method to ignore dirty logging

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Date: Fri, 15 Mar 2024 00:06:31 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Yamahata,
 Isaku" <isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Yuan, Hang" <hang.yuan@...el.com>, "Huang, Kai"
	<kai.huang@...el.com>, "Chen, Bo2" <chen.bo@...el.com>, "sagis@...gle.com"
	<sagis@...gle.com>, "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>
Subject: Re: [PATCH v19 120/130] KVM: TDX: Add a method to ignore dirty
 logging

On Mon, 2024-02-26 at 00:27 -0800, isaku.yamahata@...el.com wrote:
>  
> +static void vt_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
> +{
> +       if (KVM_BUG_ON(is_td_vcpu(vcpu), vcpu->kvm))
> +               return;
> +
> +       vmx_update_cpu_dirty_logging(vcpu);
> +}

Discussed this first part offline, but logging it here. Since
guest_memfd cannot have dirty logging, this is essentially bugging the
VM if somehow they manage anyway. But it should be blocked via the code
in check_memory_region_flags().

On the subject of warnings and KVM_BUG_ON(), my feeling so far is that
this series is quite aggressive about these. Is it due the complexity
of the series? I think maybe we can remove some of the simple ones, but
not sure if there was already some discussion on what level is
appropriate.