linux-kernel - [PATCH] kvm: Handle reads of SandyBridge RAPL PMU MSRs rather than injecting #GP

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Message-Id: <20200416184254.248374-1-jcargill@google.com>
Date:   Thu, 16 Apr 2020 11:42:54 -0700
From:   Jon Cargille <jcargill@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Venkatesh Srinivas <venkateshs@...gle.com>,
        Jon Cargille <jcargill@...gle.com>
Subject: [PATCH] kvm: Handle reads of SandyBridge RAPL PMU MSRs rather than
 injecting #GP

From: Venkatesh Srinivas <venkateshs@...gle.com>

Linux 3.14 unconditionally reads the RAPL PMU MSRs on boot, without handling
General Protection Faults on reading those MSRs. Rather than injecting a #GP,
which prevents boot, handle the MSRs by returning 0 for their data. Zero was
checked to be safe by code review of the RAPL PMU driver and in discussion
with the original driver author (eranian@...gle.com).

Signed-off-by: Venkatesh Srinivas <venkateshs@...gle.com>
Signed-off-by: Jon Cargille <jcargill@...gle.com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>
---
 arch/x86/kvm/x86.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3cc3f673785c8..4f9b7dd687e3c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3060,6 +3060,17 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_PERF_CTL:
 	case MSR_AMD64_DC_CFG:
 	case MSR_F15H_EX_CFG:
+	/*
+	 * Intel Sandy Bridge CPUs must support the RAPL (running average power
+	 * limit) MSRs. Just return 0, as we do not want to expose the host
+	 * data here. Do not conditionalize this on CPUID, as KVM does not do
+	 * so for existing CPU-specific MSRs.
+	 */
+	case MSR_RAPL_POWER_UNIT:
+	case MSR_PP0_ENERGY_STATUS:	/* Power plane 0 (core) */
+	case MSR_PP1_ENERGY_STATUS:	/* Power plane 1 (graphics uncore) */
+	case MSR_PKG_ENERGY_STATUS:	/* Total package */
+	case MSR_DRAM_ENERGY_STATUS:	/* DRAM controller */
 		msr_info->data = 0;
 		break;
 	case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
-- 
2.26.0.110.g2183baf09c-goog