linux-kernel - Re: [RFCv2 00/13] TDX and guest memory unmapping

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Message-ID: <CAPcxDJ6tkcgruegNfgPCjA3pS+-Q1iEGAZQejPhzOdx4x9cDnA@mail.gmail.com>
Date:   Thu, 22 Apr 2021 07:36:25 -0700
From:   Jue Wang <juew@...gle.com>
To:     kirill.shutemov@...ux.intel.com
Cc:     andi.kleen@...el.com, dave.hansen@...ux.intel.com,
        david@...hat.com, erdemaktas@...gle.com, isaku.yamahata@...el.com,
        jmattson@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, luto@...nel.org,
        peterz@...radead.org, pgonda@...gle.com,
        rick.p.edgecombe@...el.com, rientjes@...gle.com, seanjc@...gle.com,
        srutherford@...gle.com, x86@...nel.org
Subject: Re: [RFCv2 00/13] TDX and guest memory unmapping

On Fri, 16 Apr 2021 18:40:53 +0300, Kirill A. Shutemov wrote:

> TDX integrity check failures may lead to system shutdown host kernel must
> not allow any writes to TD-private memory. This requirment clashes with
> KVM design: KVM expects the guest memory to be mapped into host userspace
> (e.g. QEMU).

> This patchset aims to start discussion on how we can approach the issue.

Hi Kirill,

Some potential food for thought:

Repurpose Linux page hwpoison semantics for TDX-private memory protection is
smart, however, treating PG_hwpoison or hwpoison swap pte differently when
kvm->mem_protected=true implicitly disabled the original capability of page
hwpoison: protecting the whole system from known corrupted physical memory
and giving user space applications an opportunity to recover from physical
memory corruptions.

Have you considered introducing a set of similar but independent
page/pte semantics
for TDX private memory protection purpose?

Best regards,
-Jue