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From:   Denis Nikitin <denik@chromium.org>
To:     Marc Zyngier <maz@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Cc:     James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Manoj Gupta <manojgupta@google.com>,
        David Brazdil <dbrazdil@google.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        linux-kernel@vger.kernel.org, Denis Nikitin <denik@chromium.org>
Subject: [PATCH] KVM: arm64: nvhe: Disable profile optimization
Date:   Tue, 20 Sep 2022 01:20:05 -0700
Message-Id: <20220920082005.2459826-1-denik@chromium.org>
MIME-Version: 1.0
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Kernel build with -fprofile-sample-use raises the following failure:

error: arch/arm64/kvm/hyp/nvhe/kvm_nvhe.tmp.o: Unexpected SHT_REL
section ".rel.llvm.call-graph-profile"

SHT_REL is generated by the latest lld, see
https://reviews.llvm.org/rGca3bdb57fa1ac98b711a735de048c12b5fdd8086.
Disable profile optimization in kvm/nvhe to fix the build with
AutoFDO.

Signed-off-by: Denis Nikitin <denik@chromium.org>
---
 arch/arm64/kvm/hyp/nvhe/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index b5c5119c7396..6a6188374a52 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -89,6 +89,9 @@ quiet_cmd_hypcopy = HYPCOPY $@
 # Remove ftrace, Shadow Call Stack, and CFI CFLAGS.
 # This is equivalent to the 'notrace', '__noscs', and '__nocfi' annotations.
 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))
+# Profile optimization creates SHT_REL section '.llvm.call-graph-profile' for
+# the hot code. SHT_REL is currently not supported by the KVM tools.
+KBUILD_CFLAGS += $(call cc-option,-fno-profile-sample-use,-fno-profile-use)
 
 # KVM nVHE code is run at a different exception code with a different map, so
 # compiler instrumentation that inserts callbacks or checks into the code may
-- 
2.37.3.968.ga6b4b080e4-goog