linux-kernel - Re: [PATCH 7/9] KVM, VMX: add support for switching of PERF_GLOBAL

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Date:	Tue, 04 Oct 2011 11:32:03 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	joerg.roedel@....com, mingo@...e.hu, a.p.zijlstra@...llo.nl
Subject: Re: [PATCH 7/9] KVM, VMX: add support for switching of PERF_GLOBAL_CTRL

On 10/03/2011 03:49 PM, Gleb Natapov wrote:
> Some cpus have special support for switching PERF_GLOBAL_CTRL msr.
> Add logic to detect if such support exists and works properly and extend
> msr switching code to use it if available. Also extend number of generic
> msr switching entries to 8.
>
>
>   static DECLARE_BITMAP(vmx_vpid_bitmap, VMX_NR_VPIDS);
>   static DEFINE_SPINLOCK(vmx_vpid_lock);
> @@ -1195,10 +1196,29 @@ static void clear_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr)
>   {
>   	unsigned i;
>   	struct msr_autoload *m =&vmx->msr_autoload;
> +	u32 entry_load, exit_load;
> +	bool done = false;
>
> -	if (msr == MSR_EFER&&  cpu_has_load_ia32_efer) {
> -		vmcs_clear_bits(VM_ENTRY_CONTROLS, VM_ENTRY_LOAD_IA32_EFER);
> -		vmcs_clear_bits(VM_EXIT_CONTROLS, VM_EXIT_LOAD_IA32_EFER);
> +	switch (msr) {
> +	case MSR_EFER:
> +		if (cpu_has_load_ia32_efer) {
> +			entry_load = VM_ENTRY_LOAD_IA32_EFER;
> +			exit_load = VM_EXIT_LOAD_IA32_EFER;
> +			done = true;
> +		}
> +		break;
> +	case MSR_CORE_PERF_GLOBAL_CTRL:
> +		if (cpu_has_load_perf_global_ctrl) {
> +			entry_load = VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
> +			exit_load = VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
> +			done = true;
> +		}
> +		break;
> +	}
> +
> +	if (done) {
> +		vmcs_clear_bits(VM_ENTRY_CONTROLS, entry_load);
> +		vmcs_clear_bits(VM_EXIT_CONTROLS, exit_load);
>   		return;
>   	}
>
>

This is ugly.  How about

    if (msr == MSR_EFER && cpu_has_load_ia32_efer) {
        clear_atomic_switch_msr_special(VM_ENTRY_LOAD_IA32_EFER, 
VM_EXIT_LOAD_IA32_EFER);
        return;
    }

avoids the fake 'done' variable.

-- 
error compiling committee.c: too many arguments to function

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