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Fri, 26 Aug 2022 04:00:31 -0700 (PDT) X-Google-Smtp-Source: AA6agR7ukjxK7zbEStC1RaP+z3W1OcdycaKp5XVFq+gVrLjTJSIgli1jMlOF+8nJIyu2MzzDrkJ1EQ== X-Received: by 2002:a17:907:7202:b0:73d:6478:5ba5 with SMTP id dr2-20020a170907720200b0073d64785ba5mr5144663ejc.640.1661511630923; Fri, 26 Aug 2022 04:00:30 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: Peter Xu , Gavin Shan Subject: [PATCH] KVM: dirty ring: add missing memory barrier Date: Fri, 26 Aug 2022 13:00:29 +0200 Message-Id: <20220826110029.59382-1-pbonzini@redhat.com> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1661512834202100001 Content-Type: text/plain; charset="utf-8" The KVM_DIRTY_GFN_F_DIRTY flag ensures that the entry is valid. If the read of the fields are not ordered after the read of the flag, QEMU might see stale values. Cc: Peter Xu Cc: Gavin Shan Signed-off-by: Paolo Bonzini --- accel/kvm/kvm-all.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 8d81ab74de..f49643cd24 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -719,7 +719,7 @@ static void kvm_dirty_ring_mark_page(KVMState *s, uint3= 2_t as_id, =20 static bool dirty_gfn_is_dirtied(struct kvm_dirty_gfn *gfn) { - return gfn->flags =3D=3D KVM_DIRTY_GFN_F_DIRTY; + return qatomic_load_acquire(&gfn->flags, KVM_DIRTY_GFN_F_DIRTY); } =20 static void dirty_gfn_set_collected(struct kvm_dirty_gfn *gfn) --=20 2.37.1