linux-kernel - Re: [PATCH 9/9] KVM: x86: Disable intercept for Intel processor trace MSRs

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Date:   Tue, 17 Oct 2017 13:50:44 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Luwei Kang <luwei.kang@...el.com>, kvm@...r.kernel.org
CC:     pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Chao Peng <chao.p.peng@...ux.intel.com>
Subject: Re: [PATCH 9/9] KVM: x86: Disable intercept for Intel processor trace MSRs

On October 16, 2017 8:14:11 AM EDT, Luwei Kang <luwei.kang@...el.com> wrote:
>From: Chao Peng <chao.p.peng@...ux.intel.com>
>
>Trap for Intel processor trace is none sense. Pass through to
>guest directly.


And none of those MSRs can be subverted by the guest? That is none of these should be filtered / audited first?


>
>Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
>Signed-off-by: Luwei Kang <luwei.kang@...el.com>
>---
> arch/x86/kvm/vmx.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
>diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>index 3c9ce3e..58606ce 100644
>--- a/arch/x86/kvm/vmx.c
>+++ b/arch/x86/kvm/vmx.c
>@@ -7076,6 +7076,20 @@ static __init int hardware_setup(void)
> 	if (pt_mode == PT_MODE_GUEST)
> 		pt_register_virt_ops(&pt_virt_ops);
> 
>+	if (pt_mode == PT_MODE_GUEST || pt_mode == PT_MODE_HOST_GUEST) {
>+		u32 i, eax, ebx, ecx, edx;
>+
>+		cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx);
>+		vmx_disable_intercept_for_msr(MSR_IA32_RTIT_CTL, false);
>+		vmx_disable_intercept_for_msr(MSR_IA32_RTIT_STATUS, false);
>+		vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_BASE, false);
>+		vmx_disable_intercept_for_msr(MSR_IA32_RTIT_OUTPUT_MASK, false);
>+		vmx_disable_intercept_for_msr(MSR_IA32_RTIT_CR3_MATCH, false);
>+		for (i = 0; i < (eax & 0x7); i++)
>+			vmx_disable_intercept_for_msr(MSR_IA32_RTIT_ADDR0_A + i,
>+									false);
>+	}
>+
> 	return alloc_kvm_area();
> 
> out:


Thanks!