linux-kernel - Re: [PATCH 03/44] KVM: Allocate cpus_hardware

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Date:   Fri, 4 Nov 2022 13:37:45 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Atish Patra <atishp@...shpatra.org>,
        David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvmarm@...ts.cs.columbia.edu, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Chao Gao <chao.gao@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yuan Yao <yuan.yao@...el.com>
Subject: Re: [PATCH 03/44] KVM: Allocate cpus_hardware_enabled after arch
 hardware setup

On Wed, Nov 02, 2022 at 11:18:30PM +0000, Sean Christopherson wrote:
> Allocate cpus_hardware_enabled after arch hardware setup so that arch
> "init" and "hardware setup" are called back-to-back and thus can be
> combined in a future patch.  cpus_hardware_enabled is never used before
> kvm_create_vm(), i.e. doesn't have a dependency with hardware setup and
> only needs to be allocated before /dev/kvm is exposed to userspace.
>
> Free the object before the arch hooks are invoked to maintain symmetry,
> and so that arch code can move away from the hooks without having to
> worry about ordering changes.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  virt/kvm/kvm_main.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e0424af52acc..8b7534cc953b 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -5843,15 +5843,15 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>  	if (r)
>  		return r;
>
> +	r = kvm_arch_hardware_setup(opaque);
> +	if (r < 0)
> +		goto err_hw_setup;
> +
>  	if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
>  		r = -ENOMEM;
>  		goto err_hw_enabled;
>  	}
>
> -	r = kvm_arch_hardware_setup(opaque);
> -	if (r < 0)
> -		goto out_free_1;
> -
>  	c.ret = &r;
>  	c.opaque = opaque;
>  	for_each_online_cpu(cpu) {
> @@ -5937,10 +5937,10 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>  	unregister_reboot_notifier(&kvm_reboot_notifier);
>  	cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
>  out_free_2:
> -	kvm_arch_hardware_unsetup();
> -out_free_1:
>  	free_cpumask_var(cpus_hardware_enabled);
>  err_hw_enabled:
> +	kvm_arch_hardware_unsetup();
> +err_hw_setup:
>  	kvm_arch_exit();
>  	return r;
>  }
> @@ -5967,9 +5967,9 @@ void kvm_exit(void)
>  	cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
>  	on_each_cpu(hardware_disable_nolock, NULL, 1);
>  	kvm_irqfd_exit();
> +	free_cpumask_var(cpus_hardware_enabled);
>  	kvm_arch_hardware_unsetup();
>  	kvm_arch_exit();
> -	free_cpumask_var(cpus_hardware_enabled);
>  	kvm_vfio_ops_exit();

Looks good to me.

Reviewed-by: Yuan Yao <yuan.yao@...el.com>

>  }
>  EXPORT_SYMBOL_GPL(kvm_exit);
> --
> 2.38.1.431.g37b22c650d-goog
>