From nobody Sat May 30 18:38:47 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 177866674053236.63471723582268; Wed, 13 May 2026 03:05:40 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wN6Sl-000721-Ja; Wed, 13 May 2026 06:05:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wN6Si-0006yY-Cd; Wed, 13 May 2026 06:05:08 -0400 Received: from smtp25.cstnet.cn ([159.226.251.25] helo=cstnet.cn) by eggs.gnu.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1wN6Sf-0007bQ-7u; Wed, 13 May 2026 06:05:07 -0400 Received: from iscas.ac.cn (unknown [113.16.146.186]) by APP-05 (Coremail) with SMTP id zQCowADXaw+_TARqE8gkEA--.50441S2; Wed, 13 May 2026 18:04:48 +0800 (CST) From: Meng Zhuo To: qemu-riscv@nongnu.org Cc: qemu-devel@nongnu.org, Meng Zhuo Subject: [PATCH] target/riscv/kvm: skip FP/Vector sync on KVM_PUT_RUNTIME_STATE Date: Wed, 13 May 2026 18:04:47 +0800 Message-ID: <20260513100447.2167615-1-mengzhuo@iscas.ac.cn> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: zQCowADXaw+_TARqE8gkEA--.50441S2 X-Coremail-Antispam: 1UD129KBjvJXoW7Zr13urW7Wr1UCw4UKF1ftFb_yoW8Kr4xpr 45Ca9xGr1xGrWxC3yIyF4kXF1rWFWxWrZrury2y3y7KF4YkrWYgr1ktFWF9F4DCrW8ur1a 9F4jyF43u398AaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUyq14x267AKxVWUJVW8JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26r4j6ryUM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4j 6F4UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s 0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xII jxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr 1lF7xvr2IYc2Ij64vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7MxAIw28IcxkI7VAKI48J MxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwV AFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUXVWUAwCIc40Y0x0EwIxGrwCI42IY6xIIjxv2 0xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4 v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AK xVWUJVW8JbIYCTnIWIevJa73UjIFyTuYvjfU5WlkUUUUU X-Originating-IP: [113.16.146.186] X-CM-SenderInfo: pphqw6xkxrqxpvfd2hldfou0/1tbiBwsGEmoES64EdgAAsh 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=lists1p.gnu.org; Received-SPF: pass client-ip=159.226.251.25; envelope-from=mengzhuo@iscas.ac.cn; helo=cstnet.cn X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-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-ZM-MESSAGEID: 1778666743203158500 During KVM exit processing (KVM_PUT_RUNTIME_STATE), QEMU never modifies FP or Vector registers =E2=80=94 only core GPRs/PC and CSRs are potentially changed. Re-syncing 32 FP and 32 Vector registers on every KVM exit wastes 36-68 individual KVM_SET_ONE_REG ioctls per vCPU exit. Follow the s390x pattern: early return on RUNTIME after syncing core registers and CSRs. KVM_PUT_FULL_STATE and KVM_PUT_RESET_STATE continue to sync everything for correctness during migration and initialization. Signed-off-by: Meng Zhuo --- target/riscv/kvm/kvm-cpu.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c index b047ffa9c0..12a440971e 100644 --- a/target/riscv/kvm/kvm-cpu.c +++ b/target/riscv/kvm/kvm-cpu.c @@ -1373,7 +1373,7 @@ int kvm_riscv_sync_mpstate_to_kvm(RISCVCPU *cpu, int = state) =20 int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp) { - int ret =3D 0; + int ret; =20 ret =3D kvm_riscv_put_regs_core(cs); if (ret) { @@ -1385,6 +1385,17 @@ int kvm_arch_put_registers(CPUState *cs, KvmPutState= level, Error **errp) return ret; } =20 + /* + * For RUNTIME_STATE, KVM already has the correct FP and Vector state + * from the preceding KVM_RUN exit. QEMU never modifies these registers + * during exit handling, so re-syncing is unnecessary. This saves ~68 + * KVM_SET_ONE_REG ioctls per vCPU exit. See also s390x which uses + * the same pattern. + */ + if (level =3D=3D KVM_PUT_RUNTIME_STATE) { + return 0; + } + ret =3D kvm_riscv_put_regs_fp(cs); if (ret) { return ret; @@ -1395,19 +1406,17 @@ int kvm_arch_put_registers(CPUState *cs, KvmPutStat= e level, Error **errp) return ret; } =20 - if (KVM_PUT_RESET_STATE =3D=3D level) { + if (level =3D=3D KVM_PUT_RESET_STATE) { RISCVCPU *cpu =3D RISCV_CPU(cs); - if (cs->cpu_index =3D=3D 0) { - ret =3D kvm_riscv_sync_mpstate_to_kvm(cpu, KVM_MP_STATE_RUNNAB= LE); - } else { - ret =3D kvm_riscv_sync_mpstate_to_kvm(cpu, KVM_MP_STATE_STOPPE= D); - } + int state =3D cs->cpu_index =3D=3D 0 ? KVM_MP_STATE_RUNNABLE + : KVM_MP_STATE_STOPPED; + ret =3D kvm_riscv_sync_mpstate_to_kvm(cpu, state); if (ret) { return ret; } } =20 - return ret; + return 0; } =20 int kvm_arch_release_virq_post(int virq) --=20 2.47.3