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Date: Thu, 11 Jul 2019 16:40:50 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, hpa@...or.com,
dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
kvm@...r.kernel.org, x86@...nel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: konrad.wilk@...cle.com, jan.setjeeilers@...cle.com,
liran.alon@...cle.com, jwadams@...gle.com, graf@...zon.de,
rppt@...ux.vnet.ibm.com
Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation
And I've just noticed that I've messed up the subject of the cover letter.
There are 26 patches, not 27. So it should have been 00/26 not 00/27.
Sorry about that.
alex.
On 7/11/19 4:25 PM, Alexandre Chartre wrote:
> Hi,
>
> This is version 2 of the "KVM Address Space Isolation" RFC. The code
> has been completely changed compared to v1 and it now provides a generic
> kernel framework which provides Address Space Isolation; and KVM is now
> a simple consumer of that framework. That's why the RFC title has been
> changed from "KVM Address Space Isolation" to "Kernel Address Space
> Isolation".
>
> Kernel Address Space Isolation aims to use address spaces to isolate some
> parts of the kernel (for example KVM) to prevent leaking sensitive data
> between hyper-threads under speculative execution attacks. You can refer
> to the first version of this RFC for more context:
>
> https://lkml.org/lkml/2019/5/13/515
>
> The new code is still a proof of concept. It is much more stable than v1:
> I am able to run a VM with a full OS (and also a nested VM) with multiple
> vcpus. But it looks like there are still some corner cases which cause the
> system to crash/hang.
>
> I am looking for feedback about this new approach where address space
> isolation is provided by the kernel, and KVM is a just a consumer of this
> new framework.
>
>
> Changes
> =======
>
> - Address Space Isolation (ASI) is now provided as a kernel framework:
> interfaces for creating and managing an ASI are provided by the kernel,
> there are not implemented in KVM.
>
> - An ASI is associated with a page-table, we don't use mm anymore. Entering
> isolation is done by just updating CR3 to use the ASI page-table. Exiting
> isolation restores CR3 with the CR3 value present before entering isolation.
>
> - Isolation is exited at the beginning of any interrupt/exception handler,
> and on context switch.
>
> - Isolation doesn't disable interrupt, but if an interrupt occurs the
> interrupt handler will exit isolation.
>
> - The current stack is mapped when entering isolation and unmapped when
> exiting isolation.
>
> - The current task is not mapped by default, but there's an option to map it.
> In such a case, the current task is mapped when entering isolation and
> unmap when exiting isolation.
>
> - Kernel code mapped to the ASI page-table has been reduced to:
> . the entire kernel (I still need to test with only the kernel text)
> . the cpu entry area (because we need the GDT to be mapped)
> . the cpu ASI session (for managing ASI)
> . the current stack
>
> - Optionally, an ASI can request the following kernel mapping to be added:
> . the stack canary
> . the cpu offsets (this_cpu_off)
> . the current task
> . RCU data (rcu_data)
> . CPU HW events (cpu_hw_events).
>
> All these optional mappings are used for KVM isolation.
>
>
> Patches:
> ========
>
> The proposed patches provides a framework for creating an Address Space
> Isolation (ASI) (represented by a struct asi). The ASI has a page-table which
> can be populated by copying mappings from the kernel page-table. The ASI can
> then be entered/exited by switching between the kernel page-table and the
> ASI page-table. In addition, any interrupt, exception or context switch
> will automatically abort and exit the isolation. Finally patches use the
> ASI framework to implement KVM isolation.
>
> - 01-03: Core of the ASI framework: create/destroy ASI, enter/exit/abort
> isolation, ASI page-fault handler.
>
> - 04-14: Functions to manage, populate and clear an ASI page-table.
>
> - 15-20: ASI core mappings and optional mappings.
>
> - 21: Make functions to read cr3/cr4 ASI aware
>
> - 22-26: Use ASI in KVM to provide isolation for VMExit handlers.
>
>
> API Overview:
> =============
> Here is a short description of the main ASI functions provided by the framwork.
>
> struct asi *asi_create(int map_flags)
>
> Create an Address Space Isolation (ASI). map_flags can be used to specify
> optional kernel mapping to be added to the ASI page-table (for example,
> ASI_MAP_STACK_CANARY to map the stack canary).
>
>
> void asi_destroy(struct asi *asi)
>
> Destroy an ASI.
>
>
> int asi_enter(struct asi *asi)
>
> Enter isolation for the specified ASI. This switches from the kernel page-table
> to the page-table associated with the ASI.
>
>
> void asi_exit(struct asi *asi)
>
> Exit isolation for the specified ASI. This switches back to the kernel
> page-table
>
>
> int asi_map(struct asi *asi, void *ptr, unsigned long size);
>
> Copy kernel mapping to the specified ASI page-table.
>
>
> void asi_unmap(struct asi *asi, void *ptr);
>
> Clear kernel mapping from the specified ASI page-table.
>
>
> ----
> Alexandre Chartre (23):
> mm/x86: Introduce kernel address space isolation
> mm/asi: Abort isolation on interrupt, exception and context switch
> mm/asi: Handle page fault due to address space isolation
> mm/asi: Functions to track buffers allocated for an ASI page-table
> mm/asi: Add ASI page-table entry offset functions
> mm/asi: Add ASI page-table entry allocation functions
> mm/asi: Add ASI page-table entry set functions
> mm/asi: Functions to populate an ASI page-table from a VA range
> mm/asi: Helper functions to map module into ASI
> mm/asi: Keep track of VA ranges mapped in ASI page-table
> mm/asi: Functions to clear ASI page-table entries for a VA range
> mm/asi: Function to copy page-table entries for percpu buffer
> mm/asi: Add asi_remap() function
> mm/asi: Handle ASI mapped range leaks and overlaps
> mm/asi: Initialize the ASI page-table with core mappings
> mm/asi: Option to map current task into ASI
> rcu: Move tree.h static forward declarations to tree.c
> rcu: Make percpu rcu_data non-static
> mm/asi: Add option to map RCU data
> mm/asi: Add option to map cpu_hw_events
> mm/asi: Make functions to read cr3/cr4 ASI aware
> KVM: x86/asi: Populate the KVM ASI page-table
> KVM: x86/asi: Map KVM memslots and IO buses into KVM ASI
>
> Liran Alon (3):
> KVM: x86/asi: Introduce address_space_isolation module parameter
> KVM: x86/asi: Introduce KVM address space isolation
> KVM: x86/asi: Switch to KVM address space on entry to guest
>
> arch/x86/entry/entry_64.S | 42 ++-
> arch/x86/include/asm/asi.h | 237 ++++++++
> arch/x86/include/asm/mmu_context.h | 20 +-
> arch/x86/include/asm/tlbflush.h | 10 +
> arch/x86/kernel/asm-offsets.c | 4 +
> arch/x86/kvm/Makefile | 3 +-
> arch/x86/kvm/mmu.c | 2 +-
> arch/x86/kvm/vmx/isolation.c | 231 ++++++++
> arch/x86/kvm/vmx/vmx.c | 14 +-
> arch/x86/kvm/vmx/vmx.h | 24 +
> arch/x86/kvm/x86.c | 68 +++-
> arch/x86/kvm/x86.h | 1 +
> arch/x86/mm/Makefile | 2 +
> arch/x86/mm/asi.c | 459 +++++++++++++++
> arch/x86/mm/asi_pagetable.c | 1077 ++++++++++++++++++++++++++++++++++++
> arch/x86/mm/fault.c | 7 +
> include/linux/kvm_host.h | 7 +
> kernel/rcu/tree.c | 56 ++-
> kernel/rcu/tree.h | 56 +--
> kernel/sched/core.c | 4 +
> security/Kconfig | 10 +
> 21 files changed, 2269 insertions(+), 65 deletions(-)
> create mode 100644 arch/x86/include/asm/asi.h
> create mode 100644 arch/x86/kvm/vmx/isolation.c
> create mode 100644 arch/x86/mm/asi.c
> create mode 100644 arch/x86/mm/asi_pagetable.c
>
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