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

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Message-ID: <ZuKcdbXO7ImQJqbm@yilunxu-OptiPlex-7050>
Date: Thu, 12 Sep 2024 15:47:01 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"seanjc@...gle.com" <seanjc@...gle.com>,
	"Huang, Kai" <kai.huang@...el.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"nik.borisov@...e.com" <nik.borisov@...e.com>,
	"dmatlack@...gle.com" <dmatlack@...gle.com>
Subject: Re: [PATCH 13/21] KVM: TDX: Handle TLB tracking for TDX

On Wed, Sep 11, 2024 at 05:28:18PM +0000, Edgecombe, Rick P wrote:
> On Wed, 2024-09-11 at 14:25 +0800, Xu Yilun 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.
> > 
> > IIUC, private EPT is already flushed in .remove_private_spte(), so in
> > theory we don't have to invept() for private EPT?
> 
> I think you are talking about the comment, and not an optimization. So changing:

Yes, just the comment.

> "Just invoke invept() directly here to work for both shared EPT and private EPT"
> to just "Just invoke invept() directly here to work for shared EPT".

Maybe also remind invept() is redundant for private EPT in some cases,
but we implement like this for simplicity.

Thanks,
Yilun

> 
> Seems good to me.