[v2,00/50] KVM: Rework kvm_init() and hardware enabling

The main theme of this series is to kill off kvm_arch_init(),
kvm_arch_hardware_(un)setup(), and kvm_arch_check_processor_compat(), which
all originated in x86 code from way back when, and needlessly complicate
both common KVM code and architecture code.  E.g. many architectures don't
mark functions/data as __init/__ro_after_init purely because kvm_init()
isn't marked __init to support x86's separate vendor modules.

The idea/hope is that with those hooks gone (moved to arch code), it will
be easier for x86 (and other architectures) to modify their module init
sequences as needed without having to fight common KVM code.  E.g. I'm
hoping that ARM can build on this to simplify its hardware enabling logic,
especially the pKVM side of things.

There are bug fixes throughout this series.  They are more scattered than
I would usually prefer, but getting the sequencing correct was a gigantic
pain for many of the x86 fixes due to needing to fix common code in order
for the x86 fix to have any meaning.  And while the bugs are often fatal,
they aren't all that interesting for most users as they either require a
malicious admin or broken hardware, i.e. aren't likely to be encountered
by the vast majority of KVM users.  So unless someone _really_ wants a
particular fix isolated for backporting, I'm not planning on shuffling
patches.

v2:
 - Collect reviews/acks.
 - Reset eVMCS controls in VP assist page when disabling hardware. [Vitaly]
 - Clean up labels in kvm_init(). [Chao]
 - Fix a goof where VMX compat checks used boot_cpu_has. [Kai]
 - Reorder patches and/or tweak changelogs to not require time travel. [Paolo, Kai]
 - Rewrite the changelog for the patch to move ARM away from kvm_arch_init()
   to call out that it fixes theoretical bugs. [Philippe]
 - Document why it's safe to allow preemption and/or migration when
   accessing kvm_usage_count.

v1: https://lore.kernel.org/all/20221102231911.3107438-1-seanjc@google.com

Chao Gao (3):
  KVM: x86: Do compatibility checks when onlining CPU
  KVM: Rename and move CPUHP_AP_KVM_STARTING to ONLINE section
  KVM: Disable CPU hotplug during hardware enabling/disabling

Isaku Yamahata (3):
  KVM: Drop kvm_count_lock and instead protect kvm_usage_count with
    kvm_lock
  KVM: Remove on_each_cpu(hardware_disable_nolock) in kvm_exit()
  KVM: Make hardware_enable_failed a local variable in the "enable all"
    path

Marc Zyngier (1):
  KVM: arm64: Simplify the CPUHP logic

Sean Christopherson (43):
  KVM: Register /dev/kvm as the _very_ last thing during initialization
  KVM: Initialize IRQ FD after arch hardware setup
  KVM: Allocate cpus_hardware_enabled after arch hardware setup
  KVM: Teardown VFIO ops earlier in kvm_exit()
  KVM: s390: Unwind kvm_arch_init() piece-by-piece() if a step fails
  KVM: s390: Move hardware setup/unsetup to init/exit
  KVM: x86: Do timer initialization after XCR0 configuration
  KVM: x86: Move hardware setup/unsetup to init/exit
  KVM: Drop arch hardware (un)setup hooks
  KVM: VMX: Reset eVMCS controls in VP assist page during hardware
    disabling
  KVM: VMX: Don't bother disabling eVMCS static key on module exit
  KVM: VMX: Move Hyper-V eVMCS initialization to helper
  KVM: x86: Move guts of kvm_arch_init() to standalone helper
  KVM: VMX: Do _all_ initialization before exposing /dev/kvm to
    userspace
  KVM: x86: Serialize vendor module initialization (hardware setup)
  KVM: arm64: Free hypervisor allocations if vector slot init fails
  KVM: arm64: Unregister perf callbacks if hypervisor finalization fails
  KVM: arm64: Do arm/arch initialization without bouncing through
    kvm_init()
  KVM: arm64: Mark kvm_arm_init() and its unique descendants as __init
  KVM: MIPS: Hardcode callbacks to hardware virtualization extensions
  KVM: MIPS: Setup VZ emulation? directly from kvm_mips_init()
  KVM: MIPS: Register die notifier prior to kvm_init()
  KVM: RISC-V: Do arch init directly in riscv_kvm_init()
  KVM: RISC-V: Tag init functions and data with __init, __ro_after_init
  KVM: PPC: Move processor compatibility check to module init
  KVM: s390: Do s390 specific init without bouncing through kvm_init()
  KVM: s390: Mark __kvm_s390_init() and its descendants as __init
  KVM: Drop kvm_arch_{init,exit}() hooks
  KVM: VMX: Make VMCS configuration/capabilities structs read-only after
    init
  KVM: x86: Do CPU compatibility checks in x86 code
  KVM: Drop kvm_arch_check_processor_compat() hook
  KVM: x86: Use KBUILD_MODNAME to specify vendor module name
  KVM: x86: Unify pr_fmt to use module name for all KVM modules
  KVM: VMX: Use current CPU's info to perform "disabled by BIOS?" checks
  KVM: x86: Do VMX/SVM support checks directly in vendor code
  KVM: VMX: Shuffle support checks and hardware enabling code around
  KVM: SVM: Check for SVM support in CPU compatibility checks
  KVM: x86: Move CPU compat checks hook to kvm_x86_ops (from
    kvm_x86_init_ops)
  KVM: Ensure CPU is stable during low level hardware enable/disable
  KVM: Use a per-CPU variable to track which CPUs have enabled
    virtualization
  KVM: Register syscore (suspend/resume) ops early in kvm_init()
  KVM: Opt out of generic hardware enabling on s390 and PPC
  KVM: Clean up error labels in kvm_init()

 Documentation/virt/kvm/locking.rst  |  25 +-
 arch/arm64/include/asm/kvm_host.h   |  15 +-
 arch/arm64/include/asm/kvm_mmu.h    |   4 +-
 arch/arm64/kvm/Kconfig              |   1 +
 arch/arm64/kvm/arch_timer.c         |  29 +-
 arch/arm64/kvm/arm.c                |  93 +++---
 arch/arm64/kvm/mmu.c                |  12 +-
 arch/arm64/kvm/reset.c              |   8 +-
 arch/arm64/kvm/sys_regs.c           |   6 +-
 arch/arm64/kvm/vgic/vgic-init.c     |  19 +-
 arch/arm64/kvm/vmid.c               |   6 +-
 arch/mips/include/asm/kvm_host.h    |   3 +-
 arch/mips/kvm/Kconfig               |   1 +
 arch/mips/kvm/Makefile              |   2 +-
 arch/mips/kvm/callback.c            |  14 -
 arch/mips/kvm/mips.c                |  34 +--
 arch/mips/kvm/vz.c                  |   7 +-
 arch/powerpc/include/asm/kvm_host.h |   3 -
 arch/powerpc/include/asm/kvm_ppc.h  |   1 -
 arch/powerpc/kvm/book3s.c           |  12 +-
 arch/powerpc/kvm/e500.c             |   6 +-
 arch/powerpc/kvm/e500mc.c           |   6 +-
 arch/powerpc/kvm/powerpc.c          |  20 --
 arch/riscv/include/asm/kvm_host.h   |   7 +-
 arch/riscv/kvm/Kconfig              |   1 +
 arch/riscv/kvm/main.c               |  23 +-
 arch/riscv/kvm/mmu.c                |  12 +-
 arch/riscv/kvm/vmid.c               |   4 +-
 arch/s390/include/asm/kvm_host.h    |   1 -
 arch/s390/kvm/interrupt.c           |   2 +-
 arch/s390/kvm/kvm-s390.c            |  84 +++---
 arch/s390/kvm/kvm-s390.h            |   2 +-
 arch/s390/kvm/pci.c                 |   2 +-
 arch/s390/kvm/pci.h                 |   2 +-
 arch/x86/include/asm/kvm-x86-ops.h  |   1 +
 arch/x86/include/asm/kvm_host.h     |   8 +-
 arch/x86/kvm/Kconfig                |   1 +
 arch/x86/kvm/cpuid.c                |   1 +
 arch/x86/kvm/debugfs.c              |   2 +
 arch/x86/kvm/emulate.c              |   1 +
 arch/x86/kvm/hyperv.c               |   1 +
 arch/x86/kvm/i8254.c                |   4 +-
 arch/x86/kvm/i8259.c                |   4 +-
 arch/x86/kvm/ioapic.c               |   1 +
 arch/x86/kvm/irq.c                  |   1 +
 arch/x86/kvm/irq_comm.c             |   7 +-
 arch/x86/kvm/kvm_onhyperv.c         |   1 +
 arch/x86/kvm/lapic.c                |   8 +-
 arch/x86/kvm/mmu/mmu.c              |   6 +-
 arch/x86/kvm/mmu/page_track.c       |   1 +
 arch/x86/kvm/mmu/spte.c             |   4 +-
 arch/x86/kvm/mmu/spte.h             |   4 +-
 arch/x86/kvm/mmu/tdp_iter.c         |   1 +
 arch/x86/kvm/mmu/tdp_mmu.c          |   1 +
 arch/x86/kvm/mtrr.c                 |   1 +
 arch/x86/kvm/pmu.c                  |   1 +
 arch/x86/kvm/smm.c                  |   1 +
 arch/x86/kvm/svm/avic.c             |   2 +-
 arch/x86/kvm/svm/nested.c           |   2 +-
 arch/x86/kvm/svm/pmu.c              |   2 +
 arch/x86/kvm/svm/sev.c              |   1 +
 arch/x86/kvm/svm/svm.c              |  89 +++---
 arch/x86/kvm/svm/svm_onhyperv.c     |   1 +
 arch/x86/kvm/svm/svm_onhyperv.h     |   4 +-
 arch/x86/kvm/vmx/capabilities.h     |   4 +-
 arch/x86/kvm/vmx/hyperv.c           |   1 +
 arch/x86/kvm/vmx/hyperv.h           |   4 +-
 arch/x86/kvm/vmx/nested.c           |   3 +-
 arch/x86/kvm/vmx/pmu_intel.c        |   5 +-
 arch/x86/kvm/vmx/posted_intr.c      |   2 +
 arch/x86/kvm/vmx/sgx.c              |   5 +-
 arch/x86/kvm/vmx/vmcs12.c           |   1 +
 arch/x86/kvm/vmx/vmx.c              | 438 +++++++++++++++-------------
 arch/x86/kvm/vmx/vmx_ops.h          |   4 +-
 arch/x86/kvm/x86.c                  | 248 +++++++++-------
 arch/x86/kvm/xen.c                  |   1 +
 include/kvm/arm_arch_timer.h        |   6 +-
 include/kvm/arm_vgic.h              |   4 +
 include/linux/cpuhotplug.h          |   5 +-
 include/linux/kvm_host.h            |  13 +-
 virt/kvm/Kconfig                    |   3 +
 virt/kvm/kvm_main.c                 | 303 ++++++++++---------
 82 files changed, 863 insertions(+), 816 deletions(-)
 delete mode 100644 arch/mips/kvm/callback.c


base-commit: 3e04435fe60590a1c79ec94d60e9897c3ff7d73b

On Wed, Nov 30, 2022 at 11:08:44PM +0000, Sean Christopherson wrote:
>The main theme of this series is to kill off kvm_arch_init(),
>kvm_arch_hardware_(un)setup(), and kvm_arch_check_processor_compat(), which
>all originated in x86 code from way back when, and needlessly complicate
>both common KVM code and architecture code.  E.g. many architectures don't
>mark functions/data as __init/__ro_after_init purely because kvm_init()
>isn't marked __init to support x86's separate vendor modules.

Applied this series and verified that an attempt to online incompatible
CPUs (no VMX support) when some VMs are running will fail.

Queued, thanks.  I will leave this in kvm/queue after testing everything
else and moving it to kvm/next; this way, we can wait for test results
on other architectures.

Paolo

On 2022-12-27 13:02, Paolo Bonzini wrote:
> Queued, thanks.  I will leave this in kvm/queue after testing 
> everything
> else and moving it to kvm/next; this way, we can wait for test results
> on other architectures.

Can you please make this a topic branch, and if possible based
on a released -rc? It would make it a lot easier for everyone.

Thanks,

         M.

On 12/28/22 12:22, Marc Zyngier wrote:
> 
>> Queued, thanks.  I will leave this in kvm/queue after testing everything
>> else and moving it to kvm/next; this way, we can wait for test results
>> on other architectures.
> 
> Can you please make this a topic branch, and if possible based
> on a released -rc? It would make it a lot easier for everyone.

Yes, I will (it will be based on 6.2-rc1 + pull request for rc2 that I'm 
preparing + x86 changes that this conflicts with).

Paolo

On 12/28/22 12:22, Marc Zyngier wrote:
> 
>> Queued, thanks.  I will leave this in kvm/queue after testing everything
>> else and moving it to kvm/next; this way, we can wait for test results
>> on other architectures.
> 
> Can you please make this a topic branch, and if possible based
> on a released -rc? It would make it a lot easier for everyone.

This is now refs/heads/kvm-hw-enable-refactor in 
https://git.kernel.org/pub/scm/virt/kvm/kvm.git.

The commits for this series start at hash fc471e831016.

Paolo