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[209.85.208.181]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-530de478b8asm805222e87.254.2024.08.08.18.22.31 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Aug 2024 18:22:31 -0700 (PDT) Received: by mail-lj1-f181.google.com with SMTP id 38308e7fff4ca-2f149845d81so17698331fa.0 for ; Thu, 08 Aug 2024 18:22:31 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXVzJ8TScrpE1NitZRHlKKYtiS0s+DQnRWmISctcEfG2RdV7HrDJZ1wqVE+XNFgEnwL3V0LrUGiD1UKvm0P1kC2GzI= X-Received: by 2002:a2e:9917:0:b0:2ef:24dd:8d86 with SMTP id 38308e7fff4ca-2f1a6d0a79dmr700401fa.49.1723166551521; Thu, 08 Aug 2024 18:22:31 -0700 (PDT) MIME-Version: 1.0 References: <20240723144752.1478226-1-andrew.zaborowski@intel.com> <202408052135.342F9455@keescook> <6273D749-9CEC-45E4-8C56-FA3A1DBE1137@alien8.de> <20240808145331.GAZrTb60FX_I3p0Ukx@fat_crate.local> In-Reply-To: <20240808145331.GAZrTb60FX_I3p0Ukx@fat_crate.local> From: Andrew Zaborowski Date: Fri, 9 Aug 2024 03:22:19 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RESEND][PATCH 1/3] x86: Add task_struct flag to force SIGBUS on MCE To: Borislav Petkov Cc: "linux-edac@vger.kernel.org" , "linux-mm@kvack.org" , Eric Biederman , "x86@kernel.org" , Tony Luck Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: CFA3380009 X-Rspamd-Server: rspam01 X-Stat-Signature: 18benejypamwsr4wtcsus8ud6botq9xg X-HE-Tag: 1723166554-102435 X-HE-Meta: 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 fkc5mUQ0 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000018, 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 Thu, 8 Aug 2024 at 16:55, Borislav Petkov wrote: > I'm not sure it matters either. You're adding all that code and > task_struct member just because the kernel sends SIGBUS on a memory > failure. Oh well. > > How is that more beneficial for the overall recovery strategy than > killing the current task? IOW, what is the real, practical advantage of > this and why do we want to support it indefinitely? I don't have a "real world" use case, we hit these two bugs in HW testing. Qemu relies on the SIGBUS logic but the execve and rseq cases cannot be recovered from, the main benefit of sending the correct signal is perhaps information to the user. If this cannot be fixed then optimally it should be documented. As for "all that code", the memory failure handling code is of certain size and this is a comparatively tiny fix for a tiny issue. Best regards