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Date:   Thu, 16 Jun 2022 18:44:53 +0000
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From:   oliver.upton@linux.dev
Message-ID: <7b1040c48bc9b2986798322c336660ab@linux.dev>
Subject: Re: [PATCH] selftests: KVM: Handle compiler optimizations in
 ucall
To:     "David Laight" <David.Laight@aculab.com>
Cc:     "Raghavendra Rao Ananta" <rananta@google.com>,
        "Marc Zyngier" <maz@kernel.org>,
        "James Morse" <james.morse@arm.com>,
        "Alexandru Elisei" <alexandru.elisei@arm.com>,
        "Suzuki K Poulose" <suzuki.poulose@arm.com>,
        "Paolo Bonzini" <pbonzini@redhat.com>,
        "Catalin Marinas" <catalin.marinas@arm.com>,
        "Will Deacon" <will@kernel.org>, "Peter Shier" <pshier@google.com>,
        "Ricardo Koller" <ricarkol@google.com>,
        "Oliver Upton" <oupton@google.com>,
        "Reiji Watanabe" <reijiw@google.com>,
        "Jing Zhang" <jingzhangos@google.com>,
        "Colton Lewis" <coltonlewis@google.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        "Andrew Jones" <drjones@redhat.com>
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References: <3e73cb07968d4c92b797781b037c2d45@AcuMS.aculab.com>
 <20220615185706.1099208-1-rananta@google.com>
 <20220616120232.ctkekviusrozqpru@gator>
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June 16, 2022 11:48 AM, "David Laight" <David.Laight@aculab.com> wrote:=
=0A> No wonder I was confused.=0A> It's not surprising the compiler optim=
ises it all away.=0A> =0A> It doesn't seem right to be 'abusing' WRITE_ON=
CE() here.=0A> Just adding barrier() should be enough and much more descr=
iptive.=0A=0AI had the same thought, although I do not believe barrier() =
is sufficient=0Aon its own. barrier_data() with a pointer to uc passed th=
rough=0Ais required to keep clang from eliminating the dead store.=0A=0A-=
-=0AThanks,=0AOliver