linux-kernel - Re: [PATCH v11 018/113] KVM: TDX: create/destroy VM structure

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Message-ID: <Y9gXZBS2zl9nahtt@google.com>
Date:   Mon, 30 Jan 2023 19:15:48 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "zhi.wang.linux@...il.com" <zhi.wang.linux@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH v11 018/113] KVM: TDX: create/destroy VM structure

On Thu, Jan 26, 2023, Huang, Kai wrote:
> On Thu, 2023-01-26 at 21:59 +0000, Sean Christopherson wrote:
> > Hrm, but even if TDX takes a read-lock, there's still the problem of it needing
> > to walk the upper levels, i.e. KVM needs to keep mid-level page tables reachable
> > until they're fully removed.  Blech.  That should be a non-issue at this time
> > though, as I don't think KVM will ever REMOVE a page table of a live guest.  I
> > need to look at the PROMOTE/DEMOTE flows...
> 
> In this series, if I read correctly, when slot is removed/moved, private
> mappings are zapped too.  It's kinda buried in:
> 
> [PATCH v11 043/113] KVM: x86/tdp_mmu: Don't zap private pages for unsupported
> cases

That should be ok, only leaf SPTEs will be zapped in that case.