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Peter Anvin" , Helge Deller , Ingo Molnar , "James E.J. Bottomley" , John Hubbard , Liu Shixin , "Matthew Wilcox (Oracle)" , Michael Ellerman , Muchun Song , "Naveen N. Rao" , Nicholas Piggin , Peter Xu , Peter Zijlstra , Suren Baghdasaryan , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [PATCH v2 1/1] arch/fault: don't print logs for pte marker poison errors Message-ID: <20240515183222.GCZkT_tvEffgYtah4T@fat_crate.local> References: <20240510182926.763131-1-axelrasmussen@google.com> <20240510182926.763131-2-axelrasmussen@google.com> <20240515104142.GBZkSRZsa3cxJ3DKVy@fat_crate.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: ABBC04001A X-Stat-Signature: j8jdu33ugbjx3hu35tnazapzqu1fhy4f X-HE-Tag: 1715797986-256641 X-HE-Meta: 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 z03soMA1 dx/gJb2LRKgWhcyH1WikffoUSv5urrnY5e305wE4S7cK7D7Lx30tzjzRjC5srofw6dPVsCamd+QCpOWeoBKgoYsDN289aykLt+BJh8XcdhE+Rc7+BFkp51w/lJZDv2TTfDW1/liTxpA/hEuAlShPJonQoJeRENXpEYxznFFYVZwVStzuCzsTsnROR0fXhn7149hSAP1YQFdwXxJI= 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: On Wed, May 15, 2024 at 10:33:03AM -0700, Axel Rasmussen wrote: > Right, the goal is to still have the process get a SIGBUS, but to > avoid the "MCE error" log message. The basic issue is, unprivileged > users can set these markers up, and thereby completely spam up the > log. What is the real attack scenario you want to protect against? Or is this something hypothetical? > That said, one thing I'm not sure about is whether or not > VM_FAULT_SIGBUS is a viable alternative (returned for a new PTE marker > type specific to simulated poison). The goal of the simulated poison > feature is to "closely simulate" a real hardware poison event. If you > live migrate a VM from a host with real poisoned memory, to a new > host: you'd want to keep the same behavior if the guest accessed those > addresses again, so as not to confuse the guest about why it suddenly > became "un-poisoned". Well, the recovery action is to poison the page and the process should be resilient enough and allocate a new, clean page which doesn't trigger hw poison hopefully, if possible. It doesn't make a whole lotta sense if poison "remains". Hardware poison you don't want to touch a second time either - otherwise you might consume that poison and die. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette