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From: Liran Alon <liran.alon@oracle.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	David Rientjes <rientjes@google.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Kees Cook <keescook@chromium.org>, Will Drewry <wad@chromium.org>,
	"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
	"Kleen, Andi" <andi.kleen@intel.com>,
	x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [RFC 00/16] KVM protected memory extension
Date: Tue, 26 May 2020 13:16:14 +0300
Message-ID: <8866ff79-e8fd-685d-9a1d-72acff5bf6bb@oracle.com> (raw)
In-Reply-To: <20200526061721.GB48741@kernel.org>


On 26/05/2020 9:17, Mike Rapoport wrote:
> On Mon, May 25, 2020 at 04:47:18PM +0300, Liran Alon wrote:
>> On 22/05/2020 15:51, Kirill A. Shutemov wrote:
>>
>> Furthermore, I would like to point out that just unmapping guest data from
>> kernel direct-map is not sufficient to prevent all
>> guest-to-guest info-leaks via a kernel memory info-leak vulnerability. This
>> is because host kernel VA space have other regions
>> which contains guest sensitive data. For example, KVM per-vCPU struct (which
>> holds vCPU state) is allocated on slab and therefore
>> still leakable.
> Objects allocated from slab use the direct map, vmalloc() is another story.
It doesn't matter. This patch series, like XPFO, only removes guest 
memory pages from direct-map.
Not things such as KVM per-vCPU structs. That's why Julian & Marius 
(AWS), created the "Process local kernel VA region" patch-series
that declare a single PGD entry, which maps a kernelspace region, to 
have different PFN between different tasks.
For more information, see my KVM Forum talk slides I gave in previous 
reply and related AWS patch-series:
https://patchwork.kernel.org/cover/10990403/
>
>>>    - Touching direct mapping leads to fragmentation. We need to be able to
>>>      recover from it. I have a buggy patch that aims at recovering 2M/1G page.
>>>      It has to be fixed and tested properly
>> As I've mentioned above, not mapping all guest memory from 1GB hugetlbfs
>> will lead to holes in kernel direct-map which force it to not be mapped
>> anymore as a series of 1GB huge-pages.
>> This have non-trivial performance cost. Thus, I am not sure addressing this
>> use-case is valuable.
> Out of curiosity, do we actually have some numbers for the "non-trivial
> performance cost"? For instance for KVM usecase?
>
Dig into XPFO mailing-list discussions to find out...
I just remember that this was one of the main concerns regarding XPFO.

-Liran


  reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22 12:51 Kirill A. Shutemov
2020-05-22 12:51 ` [RFC 01/16] x86/mm: Move force_dma_unencrypted() to common code Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 02/16] x86/kvm: Introduce KVM memory protection feature Kirill A. Shutemov
2020-05-25 14:58   ` Vitaly Kuznetsov
2020-05-25 15:15     ` Kirill A. Shutemov
2020-05-27  5:03       ` Sean Christopherson
2020-05-27  8:39         ` Vitaly Kuznetsov
2020-05-27  8:52           ` Sean Christopherson
2020-06-03  2:09           ` Huang, Kai
2020-06-03 11:14             ` Vitaly Kuznetsov
2020-05-22 12:52 ` [RFC 03/16] x86/kvm: Make DMA pages shared Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 04/16] x86/kvm: Use bounce buffers for KVM memory protection Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 05/16] x86/kvm: Make VirtIO use DMA API in KVM guest Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 06/16] KVM: Use GUP instead of copy_from/to_user() to access guest memory Kirill A. Shutemov
2020-05-25 15:08   ` Vitaly Kuznetsov
2020-05-25 15:17     ` Kirill A. Shutemov
2020-06-01 16:35       ` Paolo Bonzini
2020-06-02 13:33         ` Kirill A. Shutemov
2020-05-26  6:14   ` Mike Rapoport
2020-05-26 21:56     ` Kirill A. Shutemov
2020-05-29 15:24   ` Kees Cook
2020-05-22 12:52 ` [RFC 07/16] KVM: mm: Introduce VM_KVM_PROTECTED Kirill A. Shutemov
2020-05-26  6:15   ` Mike Rapoport
2020-05-26 22:01     ` Kirill A. Shutemov
2020-05-26  6:40   ` John Hubbard
2020-05-26 22:04     ` Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 08/16] KVM: x86: Use GUP for page walk instead of __get_user() Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 09/16] KVM: Protected memory extension Kirill A. Shutemov
2020-05-25 15:26   ` Vitaly Kuznetsov
2020-05-25 15:34     ` Kirill A. Shutemov
2020-06-03  1:34       ` Huang, Kai
2020-05-22 12:52 ` [RFC 10/16] KVM: x86: Enabled protected " Kirill A. Shutemov
2020-05-25 15:26   ` Vitaly Kuznetsov
2020-05-26  6:16   ` Mike Rapoport
2020-05-26 21:58     ` Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 11/16] KVM: Rework copy_to/from_guest() to avoid direct mapping Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 12/16] x86/kvm: Share steal time page with host Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 13/16] x86/kvmclock: Share hvclock memory with the host Kirill A. Shutemov
2020-05-25 15:22   ` Vitaly Kuznetsov
2020-05-25 15:25     ` Kirill A. Shutemov
2020-05-25 15:42       ` Vitaly Kuznetsov
2020-05-22 12:52 ` [RFC 14/16] KVM: Introduce gfn_to_pfn_memslot_protected() Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 15/16] KVM: Handle protected memory in __kvm_map_gfn()/__kvm_unmap_gfn() Kirill A. Shutemov
2020-05-22 12:52 ` [RFC 16/16] KVM: Unmap protected pages from direct mapping Kirill A. Shutemov
2020-05-26  6:16   ` Mike Rapoport
2020-05-26 22:10     ` Kirill A. Shutemov
2020-05-25  5:27 ` [RFC 00/16] KVM protected memory extension Kirill A. Shutemov
2020-05-25 13:47 ` Liran Alon
2020-05-25 14:46   ` Kirill A. Shutemov
2020-05-25 15:56     ` Liran Alon
2020-05-26  6:17   ` Mike Rapoport
2020-05-26 10:16     ` Liran Alon [this message]
2020-05-26 11:38       ` Mike Rapoport
2020-05-27 15:45         ` Dave Hansen
2020-05-27 21:22           ` Mike Rapoport
2020-06-04 15:15 ` Marc Zyngier
2020-06-04 15:48   ` Sean Christopherson
2020-06-04 16:27     ` Marc Zyngier
2020-06-04 16:35     ` Will Deacon
2020-06-04 19:09       ` Nakajima, Jun
2020-06-04 21:03         ` Jim Mattson
2020-06-04 23:29           ` Nakajima, Jun

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