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From: Sean Christopherson <seanjc@google.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Joerg Roedel <jroedel@suse.de>,
	Yu Zhang <yu.c.zhang@linux.intel.com>,
	David Hildenbrand <david@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm list <kvm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andi Kleen <ak@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Varad Gautam <varad.gautam@suse.com>,
	Dario Faggioli <dfaggioli@suse.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	linux-mm@kvack.org, linux-coco@lists.linux.dev,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Sathyanarayanan Kuppuswamy
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>
Subject: Re: [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory
Date: Thu, 2 Sep 2021 18:57:15 +0000	[thread overview]
Message-ID: <YTEei9RBDHnRfe/B@google.com> (raw)
In-Reply-To: <b10b09b0-d5ea-b72a-106a-4e1b0df4dc66@kernel.org>

On Thu, Sep 02, 2021, Andy Lutomirski wrote:
> On 9/2/21 2:27 AM, Joerg Roedel wrote:
> > On Wed, Sep 01, 2021 at 09:07:59AM -0700, Andy Lutomirski wrote:
> >> In principle, you could actually initialize a TDX guest with all of its
> >> memory shared and all of it mapped in the host IOMMU.
> > 
> > Not sure how this works in TDX, but in SEV code fetches are always
> > treated as encrypted. So this approach would not work with SEV, not to
> > speak about attestation, which will not work with this approach either
> > :)
> > 
> 
> Oof.

TDX is kinda similar.  _All_ accesses are private if paging is disabled because
the shared bit is either bit 48 or bit 51 in the GPA, i.e. can't be reached if
paging is disabled.  The vCPU is hardcoded to start in unpaged protected mode,
so at least some amount of guest memory needs to be private.

I also could've sworn code fetches from shared memory would #VE, but I can't find
anything in the specs that confirm that.  I may be conflating TDX with SGX's #GP
on a code fetch outside of ELRANGE...

  reply	other threads:[~2021-09-02 18:57 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24  0:52 [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory Sean Christopherson
2021-08-24 10:48 ` Yu Zhang
2021-08-26  0:35   ` Sean Christopherson
2021-08-26 13:23     ` Yu Zhang
2021-08-26 10:15 ` David Hildenbrand
2021-08-26 17:05   ` Andy Lutomirski
2021-08-26 21:26     ` David Hildenbrand
2021-08-27 18:24       ` Andy Lutomirski
2021-08-27 22:28         ` Sean Christopherson
2021-08-31 19:12           ` David Hildenbrand
2021-08-31 20:45             ` Sean Christopherson
2021-09-01  7:51               ` David Hildenbrand
2021-08-27  2:31   ` Yu Zhang
2021-08-31 19:08     ` David Hildenbrand
2021-08-31 20:01       ` Andi Kleen
2021-08-31 20:15         ` David Hildenbrand
2021-08-31 20:39           ` Andi Kleen
2021-09-01  3:34             ` Yu Zhang
2021-09-01  4:53     ` Andy Lutomirski
2021-09-01  7:12       ` Tian, Kevin
2021-09-01 10:24       ` Yu Zhang
2021-09-01 16:07         ` Andy Lutomirski
2021-09-01 16:27           ` David Hildenbrand
2021-09-02  8:34             ` Yu Zhang
2021-09-02  8:44               ` David Hildenbrand
2021-09-02 11:02                 ` Yu Zhang
2021-09-02  8:19           ` Yu Zhang
2021-09-02 18:41             ` Andy Lutomirski
2021-09-07  1:33             ` Yan Zhao
2021-09-02  9:27           ` Joerg Roedel
2021-09-02 18:41             ` Andy Lutomirski
2021-09-02 18:57               ` Sean Christopherson [this message]
2021-09-02 19:07                 ` Dave Hansen
2021-09-02 20:42                   ` Andy Lutomirski
2021-08-27 22:18   ` Sean Christopherson
2021-08-31 19:07     ` David Hildenbrand
2021-08-31 21:54       ` Sean Christopherson
2021-09-01  8:09         ` David Hildenbrand
2021-09-01 15:54           ` Andy Lutomirski
2021-09-01 16:16             ` David Hildenbrand
2021-09-01 17:09               ` Andy Lutomirski
2021-09-01 16:18             ` James Bottomley
2021-09-01 16:22               ` David Hildenbrand
2021-09-01 16:31                 ` James Bottomley
2021-09-01 16:37                   ` David Hildenbrand
2021-09-01 16:45                     ` James Bottomley
2021-09-01 17:08                       ` David Hildenbrand
2021-09-01 17:50                         ` Sean Christopherson
2021-09-01 17:53                           ` David Hildenbrand
2021-09-01 17:08               ` Andy Lutomirski
2021-09-01 17:13                 ` James Bottomley
2021-09-02 10:18                 ` Joerg Roedel
2021-09-01 18:24               ` Andy Lutomirski
2021-09-01 19:26               ` Dave Hansen
2021-09-07 15:00               ` Tom Lendacky
2021-09-01  4:58       ` Andy Lutomirski
2021-09-01  7:49         ` David Hildenbrand
2021-09-02 18:47 ` Kirill A. Shutemov
2021-09-02 20:33   ` Sean Christopherson
2021-09-03 19:14     ` Kirill A. Shutemov
2021-09-03 19:15       ` Andy Lutomirski
2021-09-10 17:18         ` Kirill A. Shutemov
2021-09-15 19:58           ` Chao Peng
2021-09-15 13:51             ` David Hildenbrand
2021-09-15 14:29               ` Kirill A. Shutemov
2021-09-15 14:59                 ` David Hildenbrand
2021-09-15 15:35                   ` David Hildenbrand
2021-09-15 20:04                   ` Kirill A. Shutemov
2021-09-15 14:11             ` Kirill A. Shutemov
2021-09-16  7:36               ` Chao Peng
2021-09-16  9:24               ` Paolo Bonzini

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