linux-kernel - Re: [PATCH v2] X86/VMX: Disable VMX preemption timer if MWAIT is not intercepted

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Message-ID: <724738be-2117-3a44-8328-e3ec2f54711f@redhat.com>
Date:   Tue, 10 Apr 2018 13:07:05 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH v2] X86/VMX: Disable VMX preemption timer if MWAIT is not
 intercepted

On 10/04/2018 12:08, KarimAllah Ahmed wrote:
> @@ -11908,6 +11908,9 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc)
>  	u64 guest_tscl = kvm_read_l1_tsc(vcpu, tscl);
>  	u64 delta_tsc = max(guest_deadline_tsc, guest_tscl) - guest_tscl;
>  
> +	if (kvm_pause_in_guest(vcpu->kvm))
> +		return -EOPNOTSUPP;
> +

This is still doing a relatively expensive kvm_read_l1_tsc, so move it
even further up. :)

Paolo