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Tue, 18 Feb 2025 22:03:06 +0800 Message-ID: <88a674d7-4898-4bdd-aba9-65019bc5bb8c@linux.alibaba.com> Date: Tue, 18 Feb 2025 22:03:02 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/5] x86/mce: add EX_TYPE_EFAULT_REG as in-kernel recovery context to fix copy-from-user operations regression To: Peter Zijlstra , Borislav Petkov Cc: tony.luck@intel.com, bp@alien8.de, nao.horiguchi@gmail.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, linmiaohe@huawei.com, akpm@linux-foundation.org, jpoimboe@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, tianruidong@linux.alibaba.com References: <20250217063335.22257-1-xueshuai@linux.alibaba.com> <20250217063335.22257-4-xueshuai@linux.alibaba.com> <20250218125408.GD40464@noisy.programming.kicks-ass.net> <20250218130202.GG31462@noisy.programming.kicks-ass.net> From: Shuai Xue In-Reply-To: <20250218130202.GG31462@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 00B94180002 X-Stat-Signature: y743nu5wm9pdwjjmfr7hpctby4a6cq6f X-HE-Tag: 1739887392-260655 X-HE-Meta: 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 cuL6ivNl 2EOD1/sM1OWYS4XF4nKZIAgGdy0y1h8D960vg2Tf/8od2VUjlEFEHjhjvGmOBYkUeXg74AdILKgEZCRroeBpr/oIOVN4iDYwuR8/BgLhnDuGfzrk9oTxEuPoxoeHQ6xg03jOmN+uB0I/L+fvZFK84Tl6UJ1mO79cIhq/sRL6dZXtkL2Yj18uJfM3AFYN20l27wpl3h3xFq99ZuKo42XcDRA9NAMO9AyiULIWhoGUC/0AY2Lv4GCwEsIyHStOvM0MUOQAWJ7advlSdHcEtqOXhaQ/h6U5Y1g3TWq8XpbtjFMFGCti+VXYp6rbcJ8uskvLrOT48oU23BC40LM7xIqjaczbQN1Q2LJPl2QYKoo4Q+1EFWgPXr2avFGJ/Uar33y8rbWko14P3kL8LN/o= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2025/2/18 21:02, Peter Zijlstra 写道: > On Tue, Feb 18, 2025 at 01:54:08PM +0100, Peter Zijlstra wrote: > >> --- >> diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c >> index dac4d64dfb2a..cb021058165f 100644 >> --- a/arch/x86/kernel/cpu/mce/severity.c >> +++ b/arch/x86/kernel/cpu/mce/severity.c >> @@ -300,13 +300,12 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs) >> copy_user = is_copy_from_user(regs); >> instrumentation_end(); >> >> - switch (fixup_type) { >> - case EX_TYPE_UACCESS: >> - if (!copy_user) >> - return IN_KERNEL; >> - m->kflags |= MCE_IN_KERNEL_COPYIN; >> - fallthrough; >> + if (copy_user) { >> + m->kflags |= MCE_IN_KERNEL_COPYIN | MCE_IN_KERNEL_COPYIN; > > Typing is hard, obviously that second should'be been _RECOV. Hah, it doesn't matter, I got your point. > >> + return IN_KERNEL_RECOV > > But why are we having that bit *and* a return value saying the same > thing? Yes, it is rather redundant. I can refactor this out if @Borislav is happy with that. > >> + } >> >> + switch (fixup_type) { >> case EX_TYPE_FAULT_MCE_SAFE: >> case EX_TYPE_DEFAULT_MCE_SAFE: >> m->kflags |= MCE_IN_KERNEL_RECOV; Thanks. Shuai