Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
From:   Jue Wang <juew@google.com>
Date:   Thu, 22 Apr 2021 07:36:25 -0700
Message-ID: <CAPcxDJ6tkcgruegNfgPCjA3pS+-Q1iEGAZQejPhzOdx4x9cDnA@mail.gmail.com>
Subject: Re: [RFCv2 00/13] TDX and guest memory unmapping
To:     kirill.shutemov@linux.intel.com
Cc:     andi.kleen@intel.com, dave.hansen@linux.intel.com,
        david@redhat.com, erdemaktas@google.com, isaku.yamahata@intel.com,
        jmattson@google.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, luto@kernel.org,
        peterz@infradead.org, pgonda@google.com,
        rick.p.edgecombe@intel.com, rientjes@google.com, seanjc@google.com,
        srutherford@google.com, x86@kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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