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

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Date: Thu, 14 Mar 2024 18:35:11 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"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>,
	isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 120/130] KVM: TDX: Add a method to ignore dirty
 logging

On Fri, Mar 15, 2024 at 12:06:31AM +0000,
"Edgecombe, Rick P" <rick.p.edgecombe@...el.com> wrote:

> 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().

Will drop this patch.


> 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.

KVM_BUG_ON() was helpful at the early stage.  Because we don't hit them
recently, it's okay to remove them.  Will remove them.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>