Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20221102231911.3107438-1-seanjc@google.com> <20221102231911.3107438-45-seanjc@google.com>
In-Reply-To: <20221102231911.3107438-45-seanjc@google.com>
From:   Anup Patel <anup@brainfault.org>
Date:   Mon, 7 Nov 2022 08:53:16 +0530
Message-ID: <CAAhSdy307ziQVnq=bSJ_KO3kr0w_wqJ+zf3S54z_FHwt6VAmEg@mail.gmail.com>
Subject: Re: [PATCH 44/44] KVM: Opt out of generic hardware enabling on s390
 and PPC
To:     Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, Marc Zyngier <maz@kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Eric Farman <farman@linux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Oliver Upton <oliver.upton@linux.dev>,
        Atish Patra <atishp@atishpatra.org>,
        David Hildenbrand <david@redhat.com>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org,
        linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Isaku Yamahata <isaku.yamahata@intel.com>,
        Fabiano Rosas <farosas@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Chao Gao <chao.gao@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Yuan Yao <yuan.yao@intel.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, Nov 3, 2022 at 4:50 AM Sean Christopherson <seanjc@google.com> wrote:
>
> Allow architectures to opt out of the generic hardware enabling logic,
> and opt out on both s390 and PPC, which don't need to manually enable
> virtualization as it's always on (when available).
>
> In addition to letting s390 and PPC drop a bit of dead code, this will
> hopefully also allow ARM to clean up its related code, e.g. ARM has its
> own per-CPU flag to track which CPUs have enable hardware due to the
> need to keep hardware enabled indefinitely when pKVM is enabled.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

For KVM RISC-V:
Acked-by: Anup Patel <anup@brainfault.org>

Thanks,
Anup

> ---
>  arch/arm64/kvm/Kconfig              |  1 +
>  arch/mips/kvm/Kconfig               |  1 +
>  arch/powerpc/include/asm/kvm_host.h |  1 -
>  arch/powerpc/kvm/powerpc.c          |  5 -----
>  arch/riscv/kvm/Kconfig              |  1 +
>  arch/s390/include/asm/kvm_host.h    |  1 -
>  arch/s390/kvm/kvm-s390.c            |  6 ------
>  arch/x86/kvm/Kconfig                |  1 +
>  include/linux/kvm_host.h            |  4 ++++
>  virt/kvm/Kconfig                    |  3 +++
>  virt/kvm/kvm_main.c                 | 30 +++++++++++++++++++++++------
>  11 files changed, 35 insertions(+), 19 deletions(-)
>
> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index 815cc118c675..0a7d2116b27b 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -21,6 +21,7 @@ if VIRTUALIZATION
>  menuconfig KVM
>         bool "Kernel-based Virtual Machine (KVM) support"
>         depends on HAVE_KVM
> +       select KVM_GENERIC_HARDWARE_ENABLING
>         select MMU_NOTIFIER
>         select PREEMPT_NOTIFIERS
>         select HAVE_KVM_CPU_RELAX_INTERCEPT
> diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
> index 91d197bee9c0..29e51649203b 100644
> --- a/arch/mips/kvm/Kconfig
> +++ b/arch/mips/kvm/Kconfig
> @@ -28,6 +28,7 @@ config KVM
>         select MMU_NOTIFIER
>         select SRCU
>         select INTERVAL_TREE
> +       select KVM_GENERIC_HARDWARE_ENABLING
>         help
>           Support for hosting Guest kernels.
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 0a80e80c7b9e..959f566a455c 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -876,7 +876,6 @@ struct kvm_vcpu_arch {
>  #define __KVM_HAVE_ARCH_WQP
>  #define __KVM_HAVE_CREATE_DEVICE
>
> -static inline void kvm_arch_hardware_disable(void) {}
>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>  static inline void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) {}
>  static inline void kvm_arch_flush_shadow_all(struct kvm *kvm) {}
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 51268be60dac..ed426c9ee0e9 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -436,11 +436,6 @@ int kvmppc_ld(struct kvm_vcpu *vcpu, ulong *eaddr, int size, void *ptr,
>  }
>  EXPORT_SYMBOL_GPL(kvmppc_ld);
>
> -int kvm_arch_hardware_enable(void)
> -{
> -       return 0;
> -}
> -
>  int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>  {
>         struct kvmppc_ops *kvm_ops = NULL;
> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> index f36a737d5f96..d5a658a047a7 100644
> --- a/arch/riscv/kvm/Kconfig
> +++ b/arch/riscv/kvm/Kconfig
> @@ -20,6 +20,7 @@ if VIRTUALIZATION
>  config KVM
>         tristate "Kernel-based Virtual Machine (KVM) support (EXPERIMENTAL)"
>         depends on RISCV_SBI && MMU
> +       select KVM_GENERIC_HARDWARE_ENABLING
>         select MMU_NOTIFIER
>         select PREEMPT_NOTIFIERS
>         select KVM_MMIO
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index b1e98a9ed152..d3e4b5d7013a 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -1023,7 +1023,6 @@ extern char sie_exit;
>  extern int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc);
>  extern int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc);
>
> -static inline void kvm_arch_hardware_disable(void) {}
>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>  static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
>  static inline void kvm_arch_free_memslot(struct kvm *kvm,
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 949231f1393e..129c159ab5ee 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -248,12 +248,6 @@ debug_info_t *kvm_s390_dbf;
>  debug_info_t *kvm_s390_dbf_uv;
>
>  /* Section: not file related */
> -int kvm_arch_hardware_enable(void)
> -{
> -       /* every s390 is virtualization enabled ;-) */
> -       return 0;
> -}
> -
>  /* forward declarations */
>  static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
>                               unsigned long end);
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index fbeaa9ddef59..8e578311ca9d 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -49,6 +49,7 @@ config KVM
>         select SRCU
>         select INTERVAL_TREE
>         select HAVE_KVM_PM_NOTIFIER if PM
> +       select KVM_GENERIC_HARDWARE_ENABLING
>         help
>           Support hosting fully virtualized guest machines using hardware
>           virtualization extensions.  You will need a fairly recent
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 0b96d836a051..23c89c1e7788 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1441,8 +1441,10 @@ void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_
>  static inline void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {}
>  #endif
>
> +#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
>  int kvm_arch_hardware_enable(void);
>  void kvm_arch_hardware_disable(void);
> +#endif
>  int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
>  bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
> @@ -2074,7 +2076,9 @@ static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
>         }
>  }
>
> +#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
>  extern bool kvm_rebooting;
> +#endif
>
>  extern unsigned int halt_poll_ns;
>  extern unsigned int halt_poll_ns_grow;
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 800f9470e36b..d28df77345e1 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -86,3 +86,6 @@ config KVM_XFER_TO_GUEST_WORK
>
>  config HAVE_KVM_PM_NOTIFIER
>         bool
> +
> +config KVM_GENERIC_HARDWARE_ENABLING
> +       bool
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 859bc27091cd..6736b36cf469 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -102,9 +102,6 @@ EXPORT_SYMBOL_GPL(halt_poll_ns_shrink);
>  DEFINE_MUTEX(kvm_lock);
>  LIST_HEAD(vm_list);
>
> -static DEFINE_PER_CPU(bool, hardware_enabled);
> -static int kvm_usage_count;
> -
>  static struct kmem_cache *kvm_vcpu_cache;
>
>  static __read_mostly struct preempt_ops kvm_preempt_ops;
> @@ -146,9 +143,6 @@ static void hardware_disable_all(void);
>
>  static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
>
> -__visible bool kvm_rebooting;
> -EXPORT_SYMBOL_GPL(kvm_rebooting);
> -
>  #define KVM_EVENT_CREATE_VM 0
>  #define KVM_EVENT_DESTROY_VM 1
>  static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
> @@ -5005,6 +4999,13 @@ static struct miscdevice kvm_dev = {
>         &kvm_chardev_ops,
>  };
>
> +#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
> +__visible bool kvm_rebooting;
> +EXPORT_SYMBOL_GPL(kvm_rebooting);
> +
> +static DEFINE_PER_CPU(bool, hardware_enabled);
> +static int kvm_usage_count;
> +
>  static int __hardware_enable_nolock(void)
>  {
>         if (__this_cpu_read(hardware_enabled))
> @@ -5171,6 +5172,17 @@ static struct syscore_ops kvm_syscore_ops = {
>         .suspend = kvm_suspend,
>         .resume = kvm_resume,
>  };
> +#else /* CONFIG_KVM_GENERIC_HARDWARE_ENABLING */
> +static int hardware_enable_all(void)
> +{
> +       return 0;
> +}
> +
> +static void hardware_disable_all(void)
> +{
> +
> +}
> +#endif /* CONFIG_KVM_GENERIC_HARDWARE_ENABLING */
>
>  static void kvm_io_bus_destroy(struct kvm_io_bus *bus)
>  {
> @@ -5859,6 +5871,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
>         int r;
>         int cpu;
>
> +#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
>         r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_ONLINE, "kvm/cpu:online",
>                                       kvm_online_cpu, kvm_offline_cpu);
>         if (r)
> @@ -5866,6 +5879,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
>
>         register_reboot_notifier(&kvm_reboot_notifier);
>         register_syscore_ops(&kvm_syscore_ops);
> +#endif
>
>         /* A kmem cache lets us meet the alignment requirements of fx_save. */
>         if (!vcpu_align)
> @@ -5933,9 +5947,11 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
>                 free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
>         kmem_cache_destroy(kvm_vcpu_cache);
>  out_free_3:
> +#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
>         unregister_syscore_ops(&kvm_syscore_ops);
>         unregister_reboot_notifier(&kvm_reboot_notifier);
>         cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE);
> +#endif
>         return r;
>  }
>  EXPORT_SYMBOL_GPL(kvm_init);
> @@ -5957,9 +5973,11 @@ void kvm_exit(void)
>         kmem_cache_destroy(kvm_vcpu_cache);
>         kvm_vfio_ops_exit();
>         kvm_async_pf_deinit();
> +#ifdef CONFIG_KVM_GENERIC_HARDWARE_ENABLING
>         unregister_syscore_ops(&kvm_syscore_ops);
>         unregister_reboot_notifier(&kvm_reboot_notifier);
>         cpuhp_remove_state_nocalls(CPUHP_AP_KVM_ONLINE);
> +#endif
>         kvm_irqfd_exit();
>  }
>  EXPORT_SYMBOL_GPL(kvm_exit);
> --
> 2.38.1.431.g37b22c650d-goog
>