From patchwork Wed Sep 25 06:17:04 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Heinrich Schuchardt X-Patchwork-Id: 13811632 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 57A49CF9C6C for ; Wed, 25 Sep 2024 06:18:45 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1stLLL-00052r-MF; Wed, 25 Sep 2024 02:17:44 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1stLLI-00050X-PY; Wed, 25 Sep 2024 02:17:41 -0400 Received: from smtp-relay-canonical-0.canonical.com ([185.125.188.120]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1stLLG-0006Zm-G7; Wed, 25 Sep 2024 02:17:40 -0400 Received: from LT2ubnt.. (dynamic-046-114-104-111.46.114.pool.telefonica.de [46.114.104.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-canonical-0.canonical.com (Postfix) with ESMTPSA id 23A6F3F045; Wed, 25 Sep 2024 06:17:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1727245052; bh=dR3A/zHjjfI/7spRaVCvxh3g/ioPBZB42x3FY2qEW/M=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=RZTQohsZjUcEgBq/HJNJg0MWvpSIKifCE0HwpW69X4uBw0xUJ4JFjdk1nSQiIbRmw ZIIYZ0Dyd3gNkR4HvWaGj7cbB8Ak5pEJAXtcA+81MkCqY2uiC2fUVpHutIvGOTOn61 YbeZWNS52aaV7SS0LbO7c6dF85mHBffqvCsbdactOPGiJjlFZaJ2eV5e4a7pjH23DE oArQLAoBkZGt0arTBvzO3x16/Wb5/UwJhDfdZ4gWS9hptgQ6bA6TKGQei8VC/DngIC GXylmnUE4fxmUW5uTWt1xETxwFtr5NzWoIVThuDiwJjMTQJ2IM8I1P22BstuR5KB1s Ib6TY3sBDggkw== From: Heinrich Schuchardt To: Palmer Dabbelt , Alistair Francis , Bin Meng Cc: Weiwei Li , Daniel Henrique Barboza , Liu Zhiwei , Andrew Jones , Peter Maydell , qemu-riscv@nongnu.org, qemu-devel@nongnu.org, kvm-riscv@lists.infradead.org, Heinrich Schuchardt Subject: [PATCH v2 1/1] target/riscv: enable floating point unit Date: Wed, 25 Sep 2024 08:17:04 +0200 Message-ID: <20240925061704.12440-1-heinrich.schuchardt@canonical.com> X-Mailer: git-send-email 2.45.2 MIME-Version: 1.0 Received-SPF: pass client-ip=185.125.188.120; envelope-from=heinrich.schuchardt@canonical.com; helo=smtp-relay-canonical-0.canonical.com X-Spam_score_int: -44 X-Spam_score: -4.5 X-Spam_bar: ---- X-Spam_report: (-4.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.09, 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The status and mstatus CSRs contain bit field FS, which control if the floating point unit of RISC-V hart is enabled. There seems to be no specification prescribing the value of the field when entering S-mode from M-mode. But OpenSBI, as the leading SBI M-mode firmware, has set a precedent by enabling the FPU by setting the value of FS to 3 (dirty). In TCG mode, QEMU uses OpenSBI by default. Users can reasonably expect that software running QEMU in TCG mode and in KVM mode behaves similarly. When QEMU in KVM mode creates a vCPU, Linux' KVM code sets FS=1 (initial) in kvm_riscv_vcpu_fp_reset(). However, QEMU internally keeps a value of FS=0 (off) and then synchronizes this value into KVM. Thus VS-mode software is invoked with a disabled floating point unit. One example of software being impacted is EDK II with TLS enabled. It crashes when hitting the first floating point instruction while running QEMU with --accel kvm, and runs fine with --accel tcg. With this patch the FPU will be enabled when entering S-mode in KVM mode and when entering M-mode in TCG mode. Signed-off-by: Heinrich Schuchardt Reviewed-by: Andrew Jones --- v2: Rewrite the commit message as suggested in the v1 thread https://lore.kernel.org/qemu-riscv/20240916181633.366449-1-heinrich.schuchardt@canonical.com/ --- target/riscv/cpu.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c index 4bda754b01..c32e2721d4 100644 --- a/target/riscv/cpu.c +++ b/target/riscv/cpu.c @@ -923,6 +923,13 @@ static void riscv_cpu_reset_hold(Object *obj, ResetType type) if (mcc->parent_phases.hold) { mcc->parent_phases.hold(obj, type); } + if (riscv_has_ext(env, RVF) || riscv_has_ext(env, RVD)) { + env->mstatus = set_field(env->mstatus, MSTATUS_FS, env->misa_mxl); + for (int regnr = 0; regnr < 32; ++regnr) { + env->fpr[regnr] = 0; + } + riscv_csrrw(env, CSR_FCSR, NULL, 0, -1); + } #ifndef CONFIG_USER_ONLY env->misa_mxl = mcc->misa_mxl_max; env->priv = PRV_M;