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From: Jarkko Sakkinen <jarkko@kernel.org>
To: Chao Peng <chao.p.peng@linux.intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-api@vger.kernel.org, linux-doc@vger.kernel.org,
	qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
	Hugh Dickins <hughd@google.com>, Jeff Layton <jlayton@kernel.org>,
	"J . Bruce Fields" <bfields@fieldses.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Shuah Khan <shuah@kernel.org>, Mike Rapoport <rppt@kernel.org>,
	Steven Price <steven.price@arm.com>,
	"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
	Vlastimil Babka <vbabka@suse.cz>,
	Vishal Annapurve <vannapurve@google.com>,
	Yu Zhang <yu.c.zhang@linux.intel.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
	ak@linux.intel.com, david@redhat.com, aarcange@redhat.com,
	ddutile@redhat.com, dhildenb@redhat.com,
	Quentin Perret <qperret@google.com>,
	Michael Roth <michael.roth@amd.com>,
	mhocko@suse.com, Muchun Song <songmuchun@bytedance.com>,
	wei.w.wang@intel.com
Subject: Re: [PATCH v8 2/8] KVM: Extend the memslot to support fd-based private memory
Date: Wed, 5 Oct 2022 16:04:01 +0300	[thread overview]
Message-ID: <Yz2AwVjymt7xb1sL@kernel.org> (raw)
In-Reply-To: <20220915142913.2213336-3-chao.p.peng@linux.intel.com>

On Thu, Sep 15, 2022 at 10:29:07PM +0800, Chao Peng wrote:
> In memory encryption usage, guest memory may be encrypted with special
> key and can be accessed only by the VM itself. We call such memory
> private memory. It's valueless and sometimes can cause problem to allow
> userspace to access guest private memory. This patch extends the KVM
> memslot definition so that guest private memory can be provided though
> an inaccessible_notifier enlightened file descriptor (fd), without being
> mmaped into userspace.
> 
> This new extension, indicated by the new flag KVM_MEM_PRIVATE, adds two
> additional KVM memslot fields private_fd/private_offset to allow
> userspace to specify that guest private memory provided from the
> private_fd and guest_phys_addr mapped at the private_offset of the
> private_fd, spanning a range of memory_size.
> 
> The extended memslot can still have the userspace_addr(hva). When use, a
> single memslot can maintain both private memory through private
> fd(private_fd/private_offset) and shared memory through
> hva(userspace_addr). Whether the private or shared part is visible to
> guest is maintained by other KVM code.
> 
> Since there is no userspace mapping for private fd so we cannot
> get_user_pages() to get the pfn in KVM, instead we add a new
> inaccessible_notifier in the internal memslot structure and rely on it
> to get pfn by interacting with the memory file systems.
> 
> Together with the change, a new config HAVE_KVM_PRIVATE_MEM is added and
> right now it is selected on X86_64 for Intel TDX usage.
> 
> To make code maintenance easy, internally we use a binary compatible
> alias struct kvm_user_mem_region to handle both the normal and the
> '_ext' variants.
> 
> Co-developed-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>

What if userspace_addr would contain address of an extension structure,
if the flag is set, instead of shared address? I.e. interpret that field
differently (could be turned into union too ofc).

That idea could be at least re-used, if there's ever any new KVM_MEM_*
flags that would need an extension.

E.g. have struct kvm_userspace_memory_private, which contains shared
address, fd and the offset.

BR, Jarkko

  parent reply	other threads:[~2022-10-05 13:04 UTC|newest]

Thread overview: 97+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-15 14:29 [PATCH v8 0/8] KVM: mm: fd-based approach for supporting KVM Chao Peng
2022-09-15 14:29 ` [PATCH v8 1/8] mm/memfd: Introduce userspace inaccessible memfd Chao Peng
2022-09-19  9:12   ` David Hildenbrand
2022-09-19 19:10     ` Sean Christopherson
2022-09-21 21:10       ` Andy Lutomirski
2022-09-22 13:23         ` Wang, Wei W
2022-09-23 15:20         ` Fuad Tabba
2022-09-23 15:19       ` Fuad Tabba
2022-09-26 14:23         ` Chao Peng
2022-09-26 15:51           ` Fuad Tabba
2022-09-27 22:47             ` Sean Christopherson
2022-09-30 16:19               ` Fuad Tabba
2022-10-13 13:34                 ` Chao Peng
2022-10-17 10:31                   ` Fuad Tabba
2022-10-17 14:58                     ` Chao Peng
2022-10-17 19:05                       ` Fuad Tabba
2022-10-19 13:30                         ` Chao Peng
2022-10-18  0:33                 ` Sean Christopherson
2022-10-19 15:04                   ` Fuad Tabba
2022-09-23  0:58     ` Kirill A . Shutemov
2022-09-26 10:35       ` David Hildenbrand
2022-09-26 14:48         ` Kirill A. Shutemov
2022-09-26 14:53           ` David Hildenbrand
2022-09-27 23:23             ` Sean Christopherson
2022-09-28 13:36               ` Kirill A. Shutemov
2022-09-22 13:26   ` Wang, Wei W
2022-09-22 19:49     ` Sean Christopherson
2022-09-23  0:53       ` Kirill A . Shutemov
2022-09-23 15:20         ` Fuad Tabba
2022-09-30 16:14   ` Fuad Tabba
2022-09-30 16:23     ` Kirill A . Shutemov
2022-10-03  7:33       ` Fuad Tabba
2022-10-03 11:01         ` Kirill A. Shutemov
2022-10-04 15:39           ` Fuad Tabba
2022-10-06  8:50   ` Fuad Tabba
2022-10-06 13:04     ` Kirill A. Shutemov
2022-10-17 13:00   ` Vlastimil Babka
2022-10-17 16:19     ` Kirill A . Shutemov
2022-10-17 16:39       ` Gupta, Pankaj
2022-10-17 21:56         ` Kirill A . Shutemov
2022-10-18 13:42           ` Vishal Annapurve
2022-10-19 15:32             ` Kirill A . Shutemov
2022-10-20 10:50               ` Vishal Annapurve
2022-10-21 13:54                 ` Chao Peng
2022-10-21 16:53                   ` Sean Christopherson
2022-10-19 12:23   ` Vishal Annapurve
2022-10-21 13:47     ` Chao Peng
2022-10-21 16:18       ` Sean Christopherson
2022-10-24 14:59         ` Kirill A . Shutemov
2022-10-24 15:26           ` David Hildenbrand
2022-11-03 16:27           ` Vishal Annapurve
2022-09-15 14:29 ` [PATCH v8 2/8] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-09-16  9:14   ` Bagas Sanjaya
2022-09-16  9:53     ` Chao Peng
2022-09-26 10:26   ` Fuad Tabba
2022-09-26 14:04     ` Chao Peng
2022-09-29 22:45   ` Isaku Yamahata
2022-09-29 23:22     ` Sean Christopherson
2022-10-05 13:04   ` Jarkko Sakkinen [this message]
2022-10-05 22:05     ` Jarkko Sakkinen
2022-10-06  9:00   ` Fuad Tabba
2022-10-06 14:58   ` Jarkko Sakkinen
2022-10-06 15:07     ` Jarkko Sakkinen
2022-10-06 15:34       ` Sean Christopherson
2022-10-07 11:14         ` Jarkko Sakkinen
2022-10-07 14:58           ` Sean Christopherson
2022-10-07 21:54             ` Jarkko Sakkinen
2022-10-08 16:15               ` Jarkko Sakkinen
2022-10-08 17:35                 ` Jarkko Sakkinen
2022-10-10  8:25                   ` Chao Peng
2022-10-12  8:14                     ` Jarkko Sakkinen
2022-09-15 14:29 ` [PATCH v8 3/8] KVM: Add KVM_EXIT_MEMORY_FAULT exit Chao Peng
2022-09-16  9:17   ` Bagas Sanjaya
2022-09-16  9:54     ` Chao Peng
2022-09-15 14:29 ` [PATCH v8 4/8] KVM: Use gfn instead of hva for mmu_notifier_retry Chao Peng
2022-09-15 14:29 ` [PATCH v8 5/8] KVM: Register/unregister the guest private memory regions Chao Peng
2022-09-26 10:36   ` Fuad Tabba
2022-09-26 14:07     ` Chao Peng
2022-10-11  9:48   ` Fuad Tabba
2022-10-12  2:35     ` Chao Peng
2022-10-17 10:15       ` Fuad Tabba
2022-10-17 22:17         ` Sean Christopherson
2022-10-19 13:23           ` Chao Peng
2022-10-19 15:02             ` Fuad Tabba
2022-10-19 16:09               ` Sean Christopherson
2022-10-19 18:32                 ` Fuad Tabba
2022-09-15 14:29 ` [PATCH v8 6/8] KVM: Update lpage info when private/shared memory are mixed Chao Peng
2022-09-29 16:52   ` Isaku Yamahata
2022-09-30  8:59     ` Chao Peng
2022-09-15 14:29 ` [PATCH v8 7/8] KVM: Handle page fault for private memory Chao Peng
2022-10-14 18:57   ` Sean Christopherson
2022-10-17 14:48     ` Chao Peng
2022-09-15 14:29 ` [PATCH v8 8/8] KVM: Enable and expose KVM_MEM_PRIVATE Chao Peng
2022-10-04 14:55   ` Jarkko Sakkinen
2022-10-10  8:31     ` Chao Peng
2022-10-06  8:55   ` Fuad Tabba
2022-10-10  8:33     ` Chao Peng

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