From nobody Fri May 17 05:54:36 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; 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 ARC-Seal: i=1; a=rsa-sha256; t=1690263584; cv=none; d=zohomail.com; s=zohoarc; b=TKon9IlorUzJfhCzAqFLoJOqaQ6Oa1P3FkE1Fn0UBto7AeTdsGn/On29I+lNAYyNrB0SZUGdfz2D91WMFez4awT5x2Qu5qa7Ige9uww8elgLCygsZ2TLeSug4q6bE9HGwg5mGw3iEyArM3ghGGX4iP3HsSRYucARar1o1L4cO+4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1690263584; h=Content-Transfer-Encoding:Cc:Date:From:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:To; bh=qBO2Omcn5BargoaMfiM6gEzoIgFTjptpKB2sMLMlBk0=; b=O/ygtz/O/UXkEvz2Q7o5zhT493wCt8eIXFI4sROXlwKsUTVdNEvD/meZtAMwjYRc1Nthj/m5T2nrz4gBqD0wauLl6uGm3a8MhmeMa4bA5PIQM+tYL9MZJMmOc0tTEO6FIEy+/qepd+PEYm0PypMQEljufUhAGM2x1HvS2vXWN0c= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1690263584285937.1697243953874; Mon, 24 Jul 2023 22:39:44 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qOAkz-0000p7-73; Tue, 25 Jul 2023 01:38:49 -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 1qOAkX-0000nK-SW; Tue, 25 Jul 2023 01:38:22 -0400 Received: from forward103c.mail.yandex.net ([2a02:6b8:c03:500:1:45:d181:d103]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qOAkU-0001T1-IR; Tue, 25 Jul 2023 01:38:21 -0400 Received: from mail-nwsmtp-smtp-production-main-59.iva.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-59.iva.yp-c.yandex.net [IPv6:2a02:6b8:c0c:1e2b:0:640:94b5:0]) by forward103c.mail.yandex.net (Yandex) with ESMTP id D239060024; Tue, 25 Jul 2023 08:38:08 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-59.iva.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id 6cClcVZDfuQ0-WdPkXeM7; Tue, 25 Jul 2023 08:38:08 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=maquefel.me; s=mail; t=1690263488; bh=qBO2Omcn5BargoaMfiM6gEzoIgFTjptpKB2sMLMlBk0=; h=Message-Id:Date:Cc:Subject:To:From; b=GjibuyiM0Td72mliUJ4qIQmVxaCUgFBJO/scaMnVOEyCaWoTfKtnK3ztiNzY9Yi33 +Ajfy6ySCMr9FL7r+y8ZE7/MkT4cZRo+WCntTqa5BosNudHEYENzukx+3gFVMgw7mT BQncMoqJRt5Z7SClVGTYLN6OxnLRKXKM+2CfowBQ= Authentication-Results: mail-nwsmtp-smtp-production-main-59.iva.yp-c.yandex.net; dkim=pass header.i=@maquefel.me From: Nikita Shubin To: Weiwei Li , Daniel Henrique Barboza , Liu Zhiwei , qemu-riscv@nongnu.org, qemu-devel@nongnu.org Cc: linux@yadro.com, Nikita Shubin Subject: [PATCH] target/riscv: don't read write-only CSR Date: Tue, 25 Jul 2023 08:38:06 +0300 Message-Id: <20230725053806.9463-1-nikita.shubin@maquefel.me> X-Mailer: git-send-email 2.39.2 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=2a02:6b8:c03:500:1:45:d181:d103; envelope-from=nikita.shubin@maquefel.me; helo=forward103c.mail.yandex.net X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, 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-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @maquefel.me) X-ZM-MESSAGEID: 1690263587137100003 Content-Type: text/plain; charset="utf-8" From: Nikita Shubin In case of write-only CSR don't return illegal inst error when CSR is written and lacks read op. Signed-off-by: Nikita Shubin --- Anyway it not might be a good idea to read CSR when we are not asked for, during CSRRW or CSRRWI: "For CSRRWI, if rd=3Dx0, then the instruction shall not read the CSR and=20 shall not cause any of the side effects that might occur on a CSR read." May be i am missing something of course. --- target/riscv/csr.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/target/riscv/csr.c b/target/riscv/csr.c index ea7585329e..6d6a8821a8 100644 --- a/target/riscv/csr.c +++ b/target/riscv/csr.c @@ -3915,14 +3915,17 @@ static RISCVException riscv_csrrw_do64(CPURISCVStat= e *env, int csrno, return csr_ops[csrno].op(env, csrno, ret_value, new_value, write_m= ask); } =20 - /* if no accessor exists then return failure */ - if (!csr_ops[csrno].read) { - return RISCV_EXCP_ILLEGAL_INST; - } - /* read old value */ - ret =3D csr_ops[csrno].read(env, csrno, &old_value); - if (ret !=3D RISCV_EXCP_NONE) { - return ret; + /* don't read if ret_value=3D=3DNULL */ + if (ret_value) { + /* if no accessor exists then return failure */ + if (!csr_ops[csrno].read) { + return RISCV_EXCP_ILLEGAL_INST; + } + /* read old value */ + ret =3D csr_ops[csrno].read(env, csrno, &old_value); + if (ret !=3D RISCV_EXCP_NONE) { + return ret; + } } =20 /* write value if writable and write mask set, otherwise drop writes */ --=20 2.39.2