linux-kernel - [PATCHv15 6/9] KVM: arm64: Add a flag to disable MMIO trace for nVHE KVM

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Message-ID: <b1656f2f05147357b2b698db1196be6bab16f7f7.1652891705.git.quic_saipraka@quicinc.com>
Date:   Wed, 18 May 2022 22:14:15 +0530
From:   Sai Prakash Ranjan <quic_saipraka@...cinc.com>
To:     <arnd@...db.de>, <catalin.marinas@....com>, <rostedt@...dmis.org>
CC:     <gregkh@...uxfoundation.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <coresight@...ts.linaro.org>, <suzuki.poulose@....com>,
        <maz@...nel.org>, <quic_psodagud@...cinc.com>,
        <quic_tsoni@...cinc.com>, <will@...nel.org>,
        Sai Prakash Ranjan <quic_saipraka@...cinc.com>
Subject: [PATCHv15 6/9] KVM: arm64: Add a flag to disable MMIO trace for nVHE KVM

Add a generic flag (__DISABLE_TRACE_MMIO__) to disable MMIO
tracing in nVHE KVM as the tracepoint and MMIO logging symbols
should not be visible at nVHE KVM as there is no way to execute
them. It can also be used to disable MMIO tracing for specific
drivers.

Signed-off-by: Sai Prakash Ranjan <quic_saipraka@...cinc.com>
---
 arch/arm64/kvm/hyp/nvhe/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index f9fe4dc21b1f..87d22a18b7a5 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -4,7 +4,12 @@
 #
 
 asflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS
-ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS
+
+# Tracepoint and MMIO logging symbols should not be visible at nVHE KVM as
+# there is no way to execute them and any such MMIO access from nVHE KVM
+# will explode instantly (Words of Marc Zyngier). So introduce a generic flag
+# __DISABLE_TRACE_MMIO__ to disable MMIO tracing for nVHE KVM.
+ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS -D__DISABLE_TRACE_MMIO__
 
 hostprogs := gen-hyprel
 HOST_EXTRACFLAGS += -I$(objtree)/include
-- 
2.33.1