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Tue, 11 May 2021 00:56:59 -0700 (PDT) MIME-Version: 1.0 References: <20210430202610.1136687-1-richard.henderson@linaro.org> <20210430202610.1136687-2-richard.henderson@linaro.org> In-Reply-To: <20210430202610.1136687-2-richard.henderson@linaro.org> From: Peter Maydell Date: Tue, 11 May 2021 08:55:46 +0100 Message-ID: Subject: Re: [PATCH v6 01/82] target/arm: Add ID_AA64ZFR0 fields and isar_feature_aa64_sve2 To: Richard Henderson Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::632; envelope-from=peter.maydell@linaro.org; helo=mail-ej1-x632.google.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, 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 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-arm , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 30 Apr 2021 at 21:26, Richard Henderson wrote: > > Will be used for SVE2 isa subset enablement. > > Reviewed-by: Alex Benn=C3=A9e > Signed-off-by: Richard Henderson > --- > v2: Do not read zfr0 from kvm unless sve is available. > --- > diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c > index dff85f6db9..e8729b53fd 100644 > --- a/target/arm/kvm64.c > +++ b/target/arm/kvm64.c > @@ -567,6 +567,17 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeature= s *ahcf) > err |=3D read_sys_reg64(fdarray[2], &ahcf->isar.id_aa64mmfr2, > ARM64_SYS_REG(3, 0, 0, 7, 2)); > > + /* > + * Before v5.1, KVM did not support SVE and did not expose > + * ID_AA64ZFR0_EL1 even as RAZ. After v5.1, KVM still does > + * not expose the register to "user" requests like this > + * unless the host supports SVE. > + */ > + if (isar_feature_aa64_sve(&ahcf->isar)) { > + err |=3D read_sys_reg64(fdarray[2], &ahcf->isar.id_aa64zfr0, > + ARM64_SYS_REG(3, 0, 0, 4, 4)); > + } > + This code is earlier in the function than the place where we update ahcf->isar to set the "SVE supported bits": /* Add feature bits that can't appear until after VCPU init. */ if (sve_supported) { t =3D ahcf->isar.id_aa64pfr0; t =3D FIELD_DP64(t, ID_AA64PFR0, SVE, 1); ahcf->isar.id_aa64pfr0 =3D t; } so won't the condition here be always false ? thanks -- PMM