From mboxrd@z Thu Jan 1 00:00:00 1970 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 139C2C7618D for ; Thu, 6 Apr 2023 02:40:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pkFXQ-00010T-Ax; Wed, 05 Apr 2023 22:39:48 -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 1pkFXO-000105-4C; Wed, 05 Apr 2023 22:39:46 -0400 Received: from smtp80.cstnet.cn ([159.226.251.80] helo=cstnet.cn) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pkFXL-00015n-5X; Wed, 05 Apr 2023 22:39:45 -0400 Received: from [192.168.0.120] (unknown [180.175.29.170]) by APP-01 (Coremail) with SMTP id qwCowAD3_2PkMC5kx1ALAA--.1870S2; Thu, 06 Apr 2023 10:39:33 +0800 (CST) Message-ID: Date: Thu, 6 Apr 2023 10:39:32 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Cc: liweiwei@iscas.ac.cn, qemu-riscv@nongnu.org, qemu-devel@nongnu.org, palmer@dabbelt.com, alistair.francis@wdc.com, bin.meng@windriver.com, dbarboza@ventanamicro.com, zhiwei_liu@linux.alibaba.com, wangjunqiang@iscas.ac.cn, lazyparser@gmail.com Subject: Re: [PATCH 1/2] target/riscv: Fix the mstatus.MPP value after executing MRET Content-Language: en-US To: Alistair Francis References: <20230330135818.68417-1-liweiwei@iscas.ac.cn> <20230330135818.68417-2-liweiwei@iscas.ac.cn> <2b52f993-158e-a7ee-9180-b84f85f432c6@iscas.ac.cn> <0b8f3928-1901-b338-43a6-b436fb9013ed@iscas.ac.cn> From: liweiwei In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: qwCowAD3_2PkMC5kx1ALAA--.1870S2 X-Coremail-Antispam: 1UD129KBjvJXoWxurWxKF4rXryxKry7Xr4ruFg_yoWrAF1xpr W5GFW2kFWDJFZF93WIqw1Fgr43t3y3KryDWwn5Jr1UAFZ0qw4kuFsFyw4Y9rWDZFy0kryj vF4jk3sxZFW7ZFDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9Y14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26ryj6F1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4j 6r4UJwA2z4x0Y4vEx4A2jsIE14v26r4UJVWxJr1l84ACjcxK6I8E87Iv6xkF7I0E14v26r xl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj 6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr 0_Gr1lF7xvr2IY64vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7M4IIrI8v6xkF7I0E8cxa n2IY04v7Mxk0xIA0c2IEe2xFo4CEbIxvr21l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x 0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2 zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF 4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWU CwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCT nIWIevJa73UjIFyTuYvjfUoOJ5UUUUU X-Originating-IP: [180.175.29.170] X-CM-SenderInfo: 5olzvxxzhlqxpvfd2hldfou0/ Received-SPF: pass client-ip=159.226.251.80; envelope-from=liweiwei@iscas.ac.cn; helo=cstnet.cn X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-1.355, RCVD_IN_MSPIKE_H2=-0.001, 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: 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 On 2023/4/6 10:24, Alistair Francis wrote: > On Thu, Apr 6, 2023 at 12:14 PM liweiwei wrote: >> >> On 2023/4/6 09:46, Alistair Francis wrote: >>> On Thu, Apr 6, 2023 at 10:56 AM liweiwei wrote: >>>> On 2023/4/6 08:43, Alistair Francis wrote: >>>> >>>> On Thu, Mar 30, 2023 at 11:59 PM Weiwei Li wrote: >>>> >>>> The MPP will be set to the least-privileged supported mode (U if >>>> U-mode is implemented, else M). >>>> >>>> I don't think this is right, the spec in section 8.6.4 says this: >>>> >>>> Sorry, I didn't find this section in latest release of both privilege and un-privilege spec >>> I updated my spec, using commit >>> f6b8d5c7d2dcd935b48689a337c8f5bc2be4b5e5 it's now section 9.6.4 Trap >>> Return >> Yeah. I see it. However, this is a little different from the description >> in section 3.1.6.1. > They seem to be in conflict. It's probably worth opening an issue > against the spec to get some clarification here. OK. I'll send an issue for it. > >> And MPP is WARL field. PRV_U will be an illegal value for MPP if U-mode >> is not implemented. > Yeah, I think you are right. It just directly goes against the mret > section. I suspect the mret section is wrong and needs to be updated > >> So I think description in section 3.1.6.1 seems more reasonable. >> >>>> (draft-20230131-c0b298a: Clarify WFI trapping behavior (#972)). >>> Also, you replied with a HTML email which loses the conversation >>> history (just see above). Can you fixup your client to reply with >>> plain text please >> Sorry. I don't get your problem. I replied by Thunderbird. Above is the > Have a look at your previous email, it's a HTML email. If I view the > source of the email I see this: > > Content-Type: text/html; charset=UTF-8 > > and the formatting is a little off. > > This email that I'm replying to is a plain text email. I'm not sure > what happened, but try to check that your responses are plain text. I > think there is a setting in Thunderbird to just open and reply to all > emails as plain text, which is probably worth turning on OK . Thanks! I'll try to set it later. Regards, Weiwei Li > > Alistair > >> title for the latest release version of the spec in riscv-isa-manual >> github >> (https://github.com/riscv/riscv-isa-manual/releases/tag/draft-20230131-c0b298a). >> >> Regards, >> >> Weiwei Li >> >>> Alistair >>> >>>> "MRET then in mstatus/mstatush sets MPV=0, MPP=0, >>>> MIE=MPIE, and MPIE=1" >>>> >>>> In section 3.1.6.1, the privilege spec says this: >>>> >>>> "An MRET or SRET instruction is used to return from a trap in M-mode or S-mode respectively. >>>> When executing an xRET instruction, supposing xPP holds the value y, xIE is set to xPIE; the >>>> privilege mode is changed to y; xPIE is set to 1; and xPP is set to the least-privileged supported >>>> mode (U if U-mode is implemented, else M). If y̸=M, xRET also sets MPRV=0" >>>> >>>> And I think PRV_U is an illegal value for MPP if U-mode is not implemented. >>>> >>>> Regards, >>>> >>>> Weiwei Li >>>> >>>> So it should just always be 0 (PRV_U is 0) >>>> >>>> Alistair >>>> >>>> Signed-off-by: Weiwei Li >>>> Signed-off-by: Junqiang Wang >>>> --- >>>> target/riscv/op_helper.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c >>>> index 84ee018f7d..991f06d98d 100644 >>>> --- a/target/riscv/op_helper.c >>>> +++ b/target/riscv/op_helper.c >>>> @@ -339,7 +339,8 @@ target_ulong helper_mret(CPURISCVState *env) >>>> mstatus = set_field(mstatus, MSTATUS_MIE, >>>> get_field(mstatus, MSTATUS_MPIE)); >>>> mstatus = set_field(mstatus, MSTATUS_MPIE, 1); >>>> - mstatus = set_field(mstatus, MSTATUS_MPP, PRV_U); >>>> + mstatus = set_field(mstatus, MSTATUS_MPP, >>>> + riscv_has_ext(env, RVU) ? PRV_U : PRV_M); >>>> mstatus = set_field(mstatus, MSTATUS_MPV, 0); >>>> if ((env->priv_ver >= PRIV_VERSION_1_12_0) && (prev_priv != PRV_M)) { >>>> mstatus = set_field(mstatus, MSTATUS_MPRV, 0); >>>> -- >>>> 2.25.1 >>>> >>>>