Date:   Sat, 18 Jan 2020 21:01:05 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Marc Zyngier <maz@...nel.org>, James Hogan <jhogan@...nel.org>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>
Cc:     James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm-ppc@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kurz <groug@...d.org>,
        David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH v2 00/45] KVM: Refactor vCPU creation

Queued.  Paul, David, please test kvm/next in a couple days.

Paolo

On 18/12/19 22:54, Sean Christopherson wrote:
> The end goal of this series is to strip down the interface between common
> KVM code and arch specific code so that there is precisely one arch hook
> for creating a vCPU and one hook for destroying a vCPU.  In addition to
> cleaning up the code base, simplifying the interface gives architectures
> more freedom to organize their vCPU creation code.  Details below.
> 
> v2:
>   - Rebase to commit e41a90be9659 ("KVM: x86/mmu: WARN if root_hpa is
>     invalid when handling a page fault").  A few minor x86 (VMX) conflicts,
>     and one straightforward arm conflict with commit 8564d6372a7d ("KVM:
>     arm64: Support stolen time reporting via shared structure") in patch
>     "KVM: ARM: Move all vcpu init code into kvm_arch_vcpu_create()".
>   - Collect Reviews and Acks [Christoffer, Greg].
>   - Fix a warning in "KVM: arm64: Free sve_state via arm specific hook"
>     by using a "void" return type [Christoffer].
>   - Fix a bug in "KVM: PPC: Move kvm_vcpu_init() invocation to common code"
>     where the call in kvmppc_core_vcpu_create_e500mc() was inadvertantly
>     left behind.
> 
> 
> KVM's vCPU creation code is comically messy.  kvm_vm_ioctl_create_vcpu()
> calls three separate arch hooks: init(), create() and setup().  The init()
> call is especially nasty as it's hidden away in a common KVM function,
> kvm_init_vcpu(), that for all intents and purposes must be immediately
> invoked after the vcpu object is allocated.
> 
> Not to be outdone, vCPU destruction also has three arch hooks: uninit(),
> destroy() and free(), the latter of which isn't actually invoked by common
> KVM code, but the hook declaration still exists because architectures are
> relying on its forward declaration.
> 
> Eliminating the extra arch hooks is relatively straightforward, just
> tedious.  For the most part, there is no fundamental constraint that
> necessitated the proliferation of arch hooks, rather they crept in over
> time, usually when x86-centric code was moved out of generic KVM and into
> x86 code.
> 
> E.g. kvm_arch_vcpu_setup() was added to allow x86 to do vcpu_load(), which
> can only be done after preempt_notifier initialization, but adding setup()
> overlooked the fact that the preempt_notifier was only initialized after
> kvm_arch_vcpu_create() because preemption support was added when x86's MMU
> setup (the vcpu_load() user) was called from common KVM code.
> 
> For all intents and purposes, there is no true functional change in this
> series.  The order of some allocations will change, and a few memory leaks
> are fixed, but the actual functionality of a guest should be unaffected.
> 
> Patches 01-03 are bug fixes in error handling paths that were found by
> inspection when refactoring the associated code.
> 
> Patches 04-43 refactor each arch implementation so that the unwanted arch
> hooks can be dropped without a functional change, e.g. move code out of
> kvm_arch_vcpu_setup() so that all implementations are empty, then drop the
> functions and caller.
> 
> Patches 44-45 are minor clean up to eliminate kvm_vcpu_uninit().
> 
> The net result is to go from this:
> 
>         vcpu = kvm_arch_vcpu_create(kvm, id);
>                |
>                |-> kvm_vcpu_init()
>                    |
>                    |-> kvm_arch_vcpu_init()
> 
>         if (IS_ERR(vcpu)) {
>                 r = PTR_ERR(vcpu);
>                 goto vcpu_decrement;
>         }
> 
>         preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
> 
>         r = kvm_arch_vcpu_setup(vcpu);
>         if (r)
>                 goto vcpu_destroy;
> 
> 
> Sean Christopherson (45):
>   KVM: PPC: Book3S HV: Uninit vCPU if vcore creation fails
>   KVM: PPC: Book3S PR: Free shared page if mmu initialization fails
>   KVM: x86: Free wbinvd_dirty_mask if vCPU creation fails
>   KVM: VMX: Allocate VPID after initializing VCPU
>   KVM: VMX: Use direct vcpu pointer during vCPU create/free
>   KVM: SVM: Use direct vcpu pointer during vCPU create/free
>   KVM: x86: Allocate vcpu struct in common x86 code
>   KVM: x86: Move FPU allocation to common x86 code
>   KVM: x86: Move allocation of pio_data page down a few lines
>   KVM: x86: Move kvm_vcpu_init() invocation to common code
>   KVM: PPC: e500mc: Add build-time assert that vcpu is at offset 0
>   KVM: PPC: Allocate vcpu struct in common PPC code
>   KVM: PPC: Book3S PR: Allocate book3s and shadow vcpu after common init
>   KVM: PPC: e500mc: Move reset of oldpir below call to kvm_vcpu_init()
>   KVM: PPC: Move kvm_vcpu_init() invocation to common code
>   KVM: MIPS: Use kvm_vcpu_cache to allocate vCPUs
>   KVM: MIPS: Drop kvm_arch_vcpu_free()
>   KVM: PPC: Drop kvm_arch_vcpu_free()
>   KVM: arm: Drop kvm_arch_vcpu_free()
>   KVM: x86: Remove spurious kvm_mmu_unload() from vcpu destruction path
>   KVM: x86: Remove spurious clearing of async #PF MSR
>   KVM: x86: Drop kvm_arch_vcpu_free()
>   KVM: Remove kvm_arch_vcpu_free() declaration
>   KVM: Add kvm_arch_vcpu_precreate() to handle pre-allocation issues
>   KVM: s390: Move guts of kvm_arch_vcpu_init() into
>     kvm_arch_vcpu_create()
>   KVM: s390: Invoke kvm_vcpu_init() before allocating sie_page
>   KVM: MIPS: Invoke kvm_vcpu_uninit() immediately prior to freeing vcpu
>   KVM: x86: Invoke kvm_vcpu_uninit() immediately prior to freeing vcpu
>   KVM: Introduce kvm_vcpu_destroy()
>   KVM: Move vcpu alloc and init invocation to common code
>   KVM: Unexport kvm_vcpu_cache and kvm_vcpu_{un}init()
>   KVM: Move initialization of preempt notifier to kvm_vcpu_init()
>   KVM: x86: Move guts of kvm_arch_vcpu_setup() into
>     kvm_arch_vcpu_create()
>   KVM: MIPS: Move .vcpu_setup() call to kvm_arch_vcpu_create()
>   KVM: s390: Manually invoke vcpu setup during kvm_arch_vcpu_create()
>   KVM: PPC: BookE: Setup vcpu during kvmppc_core_vcpu_create()
>   KVM: Drop kvm_arch_vcpu_setup()
>   KVM: x86: Move all vcpu init code into kvm_arch_vcpu_create()
>   KVM: MIPS: Move all vcpu init code into kvm_arch_vcpu_create()
>   KVM: ARM: Move all vcpu init code into kvm_arch_vcpu_create()
>   KVM: PPC: Move all vcpu init code into kvm_arch_vcpu_create()
>   KVM: arm64: Free sve_state via arm specific hook
>   KVM: Drop kvm_arch_vcpu_init() and kvm_arch_vcpu_uninit()
>   KVM: Move putting of vcpu->pid to kvm_vcpu_destroy()
>   KVM: Move vcpu->run page allocation out of kvm_vcpu_init()
> 
>  arch/arm/include/asm/kvm_host.h    |   2 +-
>  arch/arm/kvm/guest.c               |   5 -
>  arch/arm64/include/asm/kvm_host.h  |   2 +-
>  arch/arm64/kvm/guest.c             |   5 -
>  arch/arm64/kvm/reset.c             |   2 +-
>  arch/mips/kvm/mips.c               |  84 ++++-------
>  arch/powerpc/include/asm/kvm_ppc.h |   6 +-
>  arch/powerpc/kvm/book3s.c          |   9 +-
>  arch/powerpc/kvm/book3s_hv.c       |  27 +---
>  arch/powerpc/kvm/book3s_pr.c       |  33 ++---
>  arch/powerpc/kvm/booke.c           |  65 ++++----
>  arch/powerpc/kvm/e500.c            |  34 +----
>  arch/powerpc/kvm/e500mc.c          |  28 +---
>  arch/powerpc/kvm/powerpc.c         |  70 ++++-----
>  arch/s390/include/asm/kvm_host.h   |   1 -
>  arch/s390/kvm/kvm-s390.c           | 110 +++++++-------
>  arch/x86/include/asm/kvm_host.h    |   2 +-
>  arch/x86/kvm/svm.c                 |  52 +------
>  arch/x86/kvm/vmx/vmx.c             |  72 +++------
>  arch/x86/kvm/x86.c                 | 230 ++++++++++++++---------------
>  include/linux/kvm_host.h           |  13 +-
>  virt/kvm/arm/arm.c                 |  80 ++++------
>  virt/kvm/kvm_main.c                |  71 +++++----
>  23 files changed, 385 insertions(+), 618 deletions(-)
> 

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