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Tsirkin" , BALATON Zoltan , Mark Cave-Ayland , Pierrick Bouvier , Zide Chen , Dapeng Mi , Zhao Liu , qemu-devel@nongnu.org, devel@lists.libvirt.org Subject: [PATCH v2 20/21] target/i386: detect user provided lbr-fmt via property flag Date: Tue, 10 Feb 2026 11:23:47 +0800 Message-Id: <20260210032348.987549-21-zhao1.liu@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260210032348.987549-1-zhao1.liu@intel.com> References: <20260210032348.987549-1-zhao1.liu@intel.com> 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=198.175.65.14; envelope-from=zhao1.liu@intel.com; helo=mgamail.intel.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @intel.com) X-ZM-MESSAGEID: 1770692440454154100 Content-Type: text/plain; charset="utf-8" At present, QEMU determines if the user has set the "lbr-fmt" property by checking if its value differs from a special value, `~PERF_CAP_LBR_FMT` (`~0x3f`). Relying on such a magic number to distinguish user input from the default state is implicit and fragile. It also prevents the helper macro `DEFINE_PROP_UINT64_CHECKMASK` from supporting a *valid* default value, as initializing the property with a valid default would make it impossible to distinguish from a user-provided value. With the introduction of `OBJ_PROP_FLAG_USER_SET`, it's possible to directly check this flag to determine whether the user has modified the property, which can help get rid of invalid "sentinel" value. Therefore, detect user-provided value by checking the USER_SET property flag in x86_cpu_realizefn(). The invalid initialization value will be dropped in subsequent work. Signed-off-by: Zhao Liu --- target/i386/cpu.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index a594747f0030..a6d943c53a3f 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -9779,6 +9779,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error= **errp) CPUX86State *env =3D &cpu->env; Error *local_err =3D NULL; unsigned requested_lbr_fmt; + int lbr_fmt_set; =20 #if defined(CONFIG_TCG) && !defined(CONFIG_USER_ONLY) /* Use pc-relative instructions in system-mode */ @@ -9815,7 +9816,11 @@ static void x86_cpu_realizefn(DeviceState *dev, Erro= r **errp) * Override env->features[FEAT_PERF_CAPABILITIES].LBR_FMT * with user-provided setting. */ - if (cpu->lbr_fmt !=3D ~PERF_CAP_LBR_FMT) { + lbr_fmt_set =3D object_property_check_flags(OBJECT(dev), "lbr-fmt", + OBJ_PROP_FLAG_USER_SET, errp= ); + if (lbr_fmt_set < 0) { + return; + } else if (lbr_fmt_set > 0) { env->features[FEAT_PERF_CAPABILITIES] &=3D ~PERF_CAP_LBR_FMT; env->features[FEAT_PERF_CAPABILITIES] |=3D cpu->lbr_fmt; } --=20 2.34.1