linux-kernel - Re: [PATCH v7 2/4] KVM: X86: Add Paravirt TLB Shootdown

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Message-ID: <20171130151715.GB1399@flask>
Date:   Thu, 30 Nov 2017 16:17:16 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v7 2/4] KVM: X86: Add Paravirt TLB Shootdown

2017-11-29 22:01-0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@...mail.com>
> ---
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> @@ -498,6 +498,34 @@ static void __init kvm_apf_trap_init(void)
>  	update_intr_gate(X86_TRAP_PF, async_page_fault);
>  }
>  
> +static DEFINE_PER_CPU(cpumask_var_t, __pv_tlb_mask);
> +
> +static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> +			const struct flush_tlb_info *info)
> +{
> +	u8 state;
> +	int cpu;
> +	struct kvm_steal_time *src;
> +	struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_tlb_mask);
> +
> +	cpumask_copy(flushmask, cpumask);

Is it impossible to call this function before the allocation?

I was guessing that early_initcall might allow us to avoid a (static)
condition as there is no point in calling when there are no others, but
expected the worst ...

thanks.