Re: [RFC PATCH v2 00/38] Nested Virtualization on KVM/ARM

[Jintack Lim]

On Fri, Jul 28, 2017 at 4:13 PM, Bandan Das <bsd@xxxxxxxxxx> wrote:
> Jintack Lim <jintack.lim@xxxxxxxxxx> writes:
> ...
>>>
>>> I'll share my experiment setup shortly.
>>
>> I summarized my experiment setup here.
>>
>> https://github.com/columbia/nesting-pub/wiki/Nested-virtualization-on-ARM-setup
>
> Thanks Jintack! I was able to test L2 boot up with these instructions.

Thanks for the confirmation!

>
> Next, I will try to run some simple tests. Any suggestions on reducing the L2 bootup
> time in my test setup ? I think I will try to make the L2 kernel print
> less messages; and maybe just get rid of some of the userspace services.
> I also applied the patch to reduce the timer frequency btw.

I think you can try to use those kernel parameters: "loglevel=1", with
which the kernel print (almost) nothing during the boot process but
the init process will print something,  or "console=none", with which
you don't see anything but the login message.  I didn't used them
because I wanted to see the L2 boot message as soon as possible :)

Thanks,
Jintack

>
> Bandan
>
>>>
>>> Even though this work has some limitations and TODOs, I'd appreciate early
>>> feedback on this RFC. Specifically, I'm interested in:
>>>
>>> - Overall design to manage vcpu context for the virtual EL2
>>> - Verifying correct EL2 register configurations such as HCR_EL2, CPTR_EL2
>>>   (Patch 30 and 32)
>>> - Patch organization and coding style
>>
>> I also wonder if the hardware and/or KVM do not support nested
>> virtualization but the userspace uses nested virtualization option,
>> which one is better: giving an error or launching a regular VM
>> silently.
>>
>>>
>>> This patch series is based on kvm/next d38338e.
>>> The whole patch series including memory, VGIC, and timer patches is available
>>> here:
>>>
>>> git@xxxxxxxxxx:columbia/nesting-pub.git rfc-v2
>>>
>>> Limitations:
>>> - There are some cases that the target exception level of a VM is ambiguous when
>>>   emulating eret instruction. I'm discussing this issue with Christoffer and
>>>   Marc. Meanwhile, I added a temporary patch (not included in this
>>>   series. f1beaba in the repo) and used 4.10.0 kernel when testing the guest
>>>   hypervisor with VHE.
>>> - Recursive nested virtualization is not tested yet.
>>> - Other hypervisors (such as Xen) on KVM are not tested.
>>>
>>> TODO:
>>> - Submit memory, VGIC, and timer patches
>>> - Evaluate regular VM performance to see if there's a negative impact.
>>> - Test other hypervisors such as Xen on KVM
>>> - Test recursive nested virtualization
>>>
>>> v1-->v2:
>>> - Added support for the virtual EL2 with VHE
>>> - Rewrote commit messages and comments from the perspective of supporting
>>>   execution environments to VMs, rather than from the perspective of the guest
>>>   hypervisor running in them.
>>> - Fixed a few bugs to make it run on the FastModel.
>>> - Tested on ARMv8.3 with four configurations. (host/guest. with/without VHE.)
>>> - Rebased to kvm/next
>>>
>>> [1] https://www.community.arm.com/processors/b/blog/posts/armv8-a-architecture-2016-additions
>>>
>>> Christoffer Dall (7):
>>>   KVM: arm64: Add KVM nesting feature
>>>   KVM: arm64: Allow userspace to set PSR_MODE_EL2x
>>>   KVM: arm64: Add vcpu_mode_el2 primitive to support nesting
>>>   KVM: arm/arm64: Add a framework to prepare virtual EL2 execution
>>>   arm64: Add missing TCR hw defines
>>>   KVM: arm64: Create shadow EL1 registers
>>>   KVM: arm64: Trap EL1 VM register accesses in virtual EL2
>>>
>>> Jintack Lim (31):
>>>   arm64: Add ARM64_HAS_NESTED_VIRT feature
>>>   KVM: arm/arm64: Enable nested virtualization via command-line
>>>   KVM: arm/arm64: Check if nested virtualization is in use
>>>   KVM: arm64: Add EL2 system registers to vcpu context
>>>   KVM: arm64: Add EL2 special registers to vcpu context
>>>   KVM: arm64: Add the shadow context for virtual EL2 execution
>>>   KVM: arm64: Set vcpu context depending on the guest exception level
>>>   KVM: arm64: Synchronize EL1 system registers on virtual EL2 entry and
>>>     exit
>>>   KVM: arm64: Move exception macros and enums to a common file
>>>   KVM: arm64: Support to inject exceptions to the virtual EL2
>>>   KVM: arm64: Trap SPSR_EL1, ELR_EL1 and VBAR_EL1 from virtual EL2
>>>   KVM: arm64: Trap CPACR_EL1 access in virtual EL2
>>>   KVM: arm64: Handle eret instruction traps
>>>   KVM: arm64: Set a handler for the system instruction traps
>>>   KVM: arm64: Handle PSCI call via smc from the guest
>>>   KVM: arm64: Inject HVC exceptions to the virtual EL2
>>>   KVM: arm64: Respect virtual HCR_EL2.TWX setting
>>>   KVM: arm64: Respect virtual CPTR_EL2.TFP setting
>>>   KVM: arm64: Add macros to support the virtual EL2 with VHE
>>>   KVM: arm64: Add EL2 registers defined in ARMv8.1 to vcpu context
>>>   KVM: arm64: Emulate EL12 register accesses from the virtual EL2
>>>   KVM: arm64: Support a VM with VHE considering EL0 of the VHE host
>>>   KVM: arm64: Allow the virtual EL2 to access EL2 states without trap
>>>   KVM: arm64: Manage the shadow states when virtual E2H bit enabled
>>>   KVM: arm64: Trap and emulate CPTR_EL2 accesses via CPACR_EL1 from the
>>>     virtual EL2 with VHE
>>>   KVM: arm64: Emulate appropriate VM control system registers
>>>   KVM: arm64: Respect the virtual HCR_EL2.NV bit setting
>>>   KVM: arm64: Respect the virtual HCR_EL2.NV bit setting for EL12
>>>     register traps
>>>   KVM: arm64: Respect virtual HCR_EL2.TVM and TRVM settings
>>>   KVM: arm64: Respect the virtual HCR_EL2.NV1 bit setting
>>>   KVM: arm64: Respect the virtual CPTR_EL2.TCPAC setting
>>>
>>>  Documentation/admin-guide/kernel-parameters.txt |   4 +
>>>  arch/arm/include/asm/kvm_emulate.h              |  17 ++
>>>  arch/arm/include/asm/kvm_host.h                 |  15 +
>>>  arch/arm64/include/asm/cpucaps.h                |   3 +-
>>>  arch/arm64/include/asm/esr.h                    |   1 +
>>>  arch/arm64/include/asm/kvm_arm.h                |   2 +
>>>  arch/arm64/include/asm/kvm_coproc.h             |   3 +-
>>>  arch/arm64/include/asm/kvm_emulate.h            |  56 ++++
>>>  arch/arm64/include/asm/kvm_host.h               |  64 ++++-
>>>  arch/arm64/include/asm/kvm_hyp.h                |  24 --
>>>  arch/arm64/include/asm/pgtable-hwdef.h          |   6 +
>>>  arch/arm64/include/asm/sysreg.h                 |  70 +++++
>>>  arch/arm64/include/uapi/asm/kvm.h               |   1 +
>>>  arch/arm64/kernel/asm-offsets.c                 |   1 +
>>>  arch/arm64/kernel/cpufeature.c                  |  11 +
>>>  arch/arm64/kvm/Makefile                         |   5 +-
>>>  arch/arm64/kvm/context.c                        | 346 +++++++++++++++++++++++
>>>  arch/arm64/kvm/emulate-nested.c                 |  83 ++++++
>>>  arch/arm64/kvm/guest.c                          |   2 +
>>>  arch/arm64/kvm/handle_exit.c                    |  89 +++++-
>>>  arch/arm64/kvm/hyp/entry.S                      |  13 +
>>>  arch/arm64/kvm/hyp/hyp-entry.S                  |   2 +-
>>>  arch/arm64/kvm/hyp/switch.c                     |  33 ++-
>>>  arch/arm64/kvm/hyp/sysreg-sr.c                  | 117 ++++----
>>>  arch/arm64/kvm/inject_fault.c                   |  12 -
>>>  arch/arm64/kvm/nested.c                         |  63 +++++
>>>  arch/arm64/kvm/reset.c                          |   8 +
>>>  arch/arm64/kvm/sys_regs.c                       | 359 +++++++++++++++++++++++-
>>>  arch/arm64/kvm/sys_regs.h                       |   8 +
>>>  arch/arm64/kvm/trace.h                          |  43 ++-
>>>  virt/kvm/arm/arm.c                              |  20 ++
>>>  31 files changed, 1363 insertions(+), 118 deletions(-)
>>>  create mode 100644 arch/arm64/kvm/context.c
>>>  create mode 100644 arch/arm64/kvm/emulate-nested.c
>>>  create mode 100644 arch/arm64/kvm/nested.c
>>>
>>> --
>>> 1.9.1
>>>