Hi Christoffer, On Mon, Jul 31, 2017 at 9:00 AM, Christoffer Dall <cdall@xxxxxxxxxx> wrote: > Hi Jintack, > > On Tue, Jul 18, 2017 at 11:58:26AM -0500, Jintack Lim wrote: >> Nested virtualization is the ability to run a virtual machine inside another >> virtual machine. In other words, it’s about running a hypervisor (the guest >> hypervisor) on top of another hypervisor (the host hypervisor). >> >> Supporting nested virtualization on ARM means that the hypervisor provides not >> only EL0/EL1 execution environment to VMs as it usually does but also the >> virtualization extensions including EL2 execution environment. Once the host >> hypervisor provides those execution environments to the VMs, then the guest >> hypervisor can run its own VMs (nested VMs) naturally. >> >> This series supports nested virtualization on arm64. ARM recently announced an >> extension (ARMv8.3) which has support for nested virtualization[1]. This patch >> set is based on the ARMv8.3 specification and tested on the FastModel with >> ARMv8.3 extension. >> >> The whole patch set to support nested virtualization is huge over 70 >> patches, so I categorized them into four parts: CPU, memory, VGIC, and timer >> virtualization. This patch series is the first part. >> >> CPU virtualization patch series provides basic nested virtualization framework >> and instruction emulations including v8.1 VHE feature and v8.3 nested >> virtualization feature for VMs. >> >> This patch series again can be divided into four parts. Patch 1 to 5 introduces >> nested virtualization by discovering hardware feature, adding a kernel >> parameter and allowing the userspace to set the initial CPU mode to EL2. >> >> Patch 6 to 25 are to support the EL2 execution environment, the virtual EL2, to >> a VM on v8.0 architecture. We de-privilege the guest hypervisor and emulate the >> virtual EL2 mode in EL1 using the hardware features provided by ARMv8.3; The >> host hypervisor manages virtual EL2 register state for the guest hypervisor >> and shadow EL1 register state that reflects the virtual EL2 register state to >> run the guest hypervisor in EL1. >> >> Patch 26 to 33 add support for the virtual EL2 with Virtualization Host >> Extensions. These patches emulate newly defined registers and bits in v8.1 and >> allow the virtual EL2 to access EL2 register states via EL1 register accesses >> as in the real EL2. >> >> Patch 34 to 38 are to support for the virtual EL2 with nested virtualization. >> These enable recursive nested virtualization. >> >> This patch set is tested on the FastModel with the v8.3 extension for arm64 and >> a cubietruck for arm32. On the FastModel, the host and the guest kernels are >> compiled with and without VHE, so there are four combinations. I was able to >> boot SMP Linux in the nested VM on all four configurations and able to run >> hackbench. I also checked that regular VMs could boot when the nested >> virtualization kernel parameter was not set. On the cubietruck, I also verified >> that regular VMs could boot as well. >> >> I'll share my experiment setup shortly. >> >> 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 >> >> 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 >> > > I think this overall looks pretty good, and I think you can drop the RFC > tag from the next revision, assuming the remaining patch sets for > memory, vgic, and timers don't require some major controversial rework > of these patches. Thank you for your thorough review. I'm happy that we can drop the RFC tag :). Thanks, Jintack > > Thanks, > -Christoffer > >> 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 >>
