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h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=GeDzh8jA6WHp/CxKP0OUKid/aof8nCv7fI6c2Z6/esAnHXjkaYY5h9T5qBYA9bGhq F55tRn31n4Ja8nd0kjwpooY0qXEZqPg8h1XltOwsqwEkCHWla6jI1W+mpSOniWCRIO cTyHNZY3uVgxbGTuAFKDeJwSGtCFDksU0Z+GPvAzFL5FBR55w5FH6CZgbi9tFUZsPn k2ABDr0oG0AhvA7h+BD/cjpRdlJgEyEx15b8i2C4yiSrz5fsFFUjSIiLUzFggCeJGR YlQ9eFU/CVl4LE6PzYCHykNQPZyO+jrzwfwt0NvBg/RPWeZq4aZfX8orOhWYPBGycq yqEI3TKmy0F+w== Received: by mail-ed1-f53.google.com with SMTP id 4fb4d7f45d1cf-55569b59f81so4974406a12.1 for ; Tue, 02 Jan 2024 03:21:05 -0800 (PST) X-Gm-Message-State: AOJu0Yw2WsQXDFS3sec6OZWXujnhllqU+3mae8h+88EwYx2BGC/YZhg+ +7Gs8N3U8QuBZy4uI42K/SVN2mOK3jszfVc4Vi8= X-Google-Smtp-Source: AGHT+IFlsPq24WCd2yxgqmcSvJkW3nbzdQEW3v5ivSTAT0THQwBtZN9+rL4w0A9AFZUm25f69rf/1O7XVxbOBueUL+0= X-Received: by 2002:a17:906:7399:b0:a23:68ec:a863 with SMTP id f25-20020a170906739900b00a2368eca863mr7697697ejl.87.1704194463900; Tue, 02 Jan 2024 03:21:03 -0800 (PST) MIME-Version: 1.0 References: <20240102101711.10872-2-xry111@xry111.site> <7a6aa1bbdbbe2e63ae96ff163fab0349f58f1b9e.camel@xry111.site> In-Reply-To: <7a6aa1bbdbbe2e63ae96ff163fab0349f58f1b9e.camel@xry111.site> From: Huacai Chen Date: Tue, 2 Jan 2024 19:20:57 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: MIPS: fcsr31 may be dirty after execve when kernel preempt is enabled (was: Re: [PATCH v2] LoongArch: Fix and simplify fcsr initialization on execve) To: Xi Ruoyao Cc: WANG Xuerui , Jiaxun Yang , Eric Biederman , Kees Cook , Tiezhu Yang , Jinyang He , loongarch@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-mips@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: A5DC640014 X-Rspam-User: X-Stat-Signature: 8jwtah3rufqrtfok9arcubm93hasmx9c X-Rspamd-Server: rspam03 X-HE-Tag: 1704194466-526218 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000062, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jan 2, 2024 at 6:48=E2=80=AFPM Xi Ruoyao wrote= : > > On Tue, 2024-01-02 at 18:25 +0800, Xi Ruoyao wrote: > > On Tue, 2024-01-02 at 18:17 +0800, Xi Ruoyao wrote: > > > The only other architecture setting FCSR in SET_PERSONALITY2 is MIPS. > > > They do this for supporting different FP flavors (NaN encodings etc). > > > which do not exist on LoongArch. I'm not sure how MIPS evades the is= sue > > > (or maybe it's just buggy too) but I'll investigate it later. > > > > Phew. I just managed to recommission my 3A4000 and I can reproduce the > > issue as well with Linux 5.18.1 (the latest kernel release when I > > decommissioned it) and CONFIG_PREEMPT=3Dy. > > > > % cat measure.c > > #include > > int main() { return fetestexcept(FE_INEXACT); } > > > > % echo $((1./3)) > > 0.33333333333333331 > > > > % while ./a.out; do ; done > > (stopped in seconds) > > > > I'm building the mainline kernel on the 3A4000 now, will see if the > > issue still exists... > > Still happening with 6.7.0-rc8. I'm not sure how to fix it for MIPS. > Maybe lose_fpu in SET_PERSONALITY2? But to me doing so will be really > nasty. Anyway I'll leave this for MIPS maintainers. Disable preemption in SET_PERSONALITY2 and enable in START_THREAD? Huacai > > -- > Xi Ruoyao > School of Aerospace Science and Technology, Xidian University