linux-kernel - Re: [PATCH 3/3] x86/kvm/vmx: avoid expensive rdmsr for MSR_GS

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Message-ID: <CALCETrUnKsNh8mbe-F=i8ZpcbbH8hDo4WmDPdmF9vEGLYk75+w@mail.gmail.com>
Date:   Mon, 12 Mar 2018 15:42:23 +0000
From:   Andy Lutomirski <luto@...nel.org>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm list <kvm@...r.kernel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 3/3] x86/kvm/vmx: avoid expensive rdmsr for MSR_GS_BASE

On Mon, Mar 12, 2018 at 2:03 PM, Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
> vmx_save_host_state() is only called from kvm_arch_vcpu_ioctl_run() so
> the context is pretty well defined and as we're past 'swapgs' MSR_GS_BASE
> should contain kernel's GS base which we point to irq_stack_union.
>
> Add new kernelmode_gs_base() API, irq_stack_union needs to be exported
> as KVM can be build as module.
>

Acked-by: Andy Lutomirski <luto@...nel.org>