From patchwork Thu Jun 29 20:50:40 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 698220 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B169EC0015E for ; Thu, 29 Jun 2023 20:51:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232542AbjF2Uvv (ORCPT ); Thu, 29 Jun 2023 16:51:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232311AbjF2Uu7 (ORCPT ); Thu, 29 Jun 2023 16:50:59 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D93B35B7 for ; Thu, 29 Jun 2023 13:50:58 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id 3f1490d57ef6-c38c87ea9ceso1716875276.1 for ; Thu, 29 Jun 2023 13:50:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688071857; x=1690663857; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=yLzMk6njG0VUm6oo8ECi7NNqjOvlkj+YcLB9LCE7+MA=; b=vd6FO9RKLDqV//QD3xfOnLM9ABYCd6dUPJXpRHT4NX5noS8/sUBwSo898iH3nVkB0i DtNAyV+Pi6bgq0S9jGXWkBhQ9/YdQKbSPEohpFeN8NdUWPbX25v+l+vYnpTa7r6jcPht dbVhBKQwNHFgV1WouNWGszv4XwOpqInDK4ouCSz6Ak/7s9gGDRqjeI3/ZhamBO61VWCa Z6gPSDN+iIv39tWkyOgXo6urQM1zLyzmqO53tLfzCPB+LOgT197q6GD2uuEhk9CDZuub vqBRd9kZ1XKyBS+VrCDyZJ59YXT8sSu0AY+uPtiN0Du5fb03DdmO0Rm9zeWUxhbXnaCv j0ow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688071857; x=1690663857; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=yLzMk6njG0VUm6oo8ECi7NNqjOvlkj+YcLB9LCE7+MA=; b=EjRW7QN5LiOfVovR1zQsPzCo/kTYXFzrdj+NaiZTsv6gW6YKs51f/MMr9hX/ocSFge MYeh9qsnccsXMWPTGrtT4M3MJ6OrTdSpdjstFIO0BSIirI57LZ335GtcAl+qHMcub00A CY4ci5zCg4W87tQP9r3zsDnIWnyHVtwr+2exfa2IB8ruKq0wC+iswJlfj+TeV/VUtfgA TFAMZrsGkreolgRQ4ofbZdNM+oS4tksIs9Q8Dy25hmqM4fUfighij3WIFamjlJqYAZVw 7NZP7aWf3oeCEwfNmHeqkyhW4Mg+kK2N2T0YpLvjo24l4Q+SVgGvMjb0Zx1bvOwYnX/g zUCA== X-Gm-Message-State: ABy/qLaWvTeU2DbzHNRmQxpjp9g8IL1I+FvSbDtqC4S2sIOKZsM1dT8z DJlwIYEX9q3Ey6+zAWV4cAElQT405WaVj79Qk6Bq X-Google-Smtp-Source: APBJJlFxXqx6n/8cIVb44SOqXuMVe8nfJc8KbVSjzubcNqQNTjaVwvxr+Cfitw1Wlj4qp7VAwfdaVDGWjSlIa4+NsAGc X-Received: from axel.svl.corp.google.com ([2620:15c:2a3:200:e20f:5917:3efa:d4bb]) (user=axelrasmussen job=sendgmr) by 2002:a05:6902:1105:b0:bc3:cdb7:4ec8 with SMTP id o5-20020a056902110500b00bc3cdb74ec8mr74829ybu.6.1688071857157; Thu, 29 Jun 2023 13:50:57 -0700 (PDT) Date: Thu, 29 Jun 2023 13:50:40 -0700 In-Reply-To: <20230629205040.665834-1-axelrasmussen@google.com> Mime-Version: 1.0 References: <20230629205040.665834-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.41.0.255.g8b1d071c50-goog Message-ID: <20230629205040.665834-6-axelrasmussen@google.com> Subject: [PATCH v2 6/6] mm: userfaultfd: add basic documentation for UFFDIO_POISON From: Axel Rasmussen To: Alexander Viro , Andrew Morton , Christian Brauner , David Hildenbrand , Huang Ying , Hugh Dickins , James Houghton , Jiaqi Yan , Jonathan Corbet , "Liam R. Howlett" , Miaohe Lin , Mike Kravetz , "Mike Rapoport (IBM)" , Muchun Song , Nadav Amit , Naoya Horiguchi , Peter Xu , Shuah Khan , ZhangPeng Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Axel Rasmussen Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Just describe the feature at a really basic level. Signed-off-by: Axel Rasmussen Acked-by: Peter Xu --- Documentation/admin-guide/mm/userfaultfd.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 7c304e432205..b19053436369 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -244,6 +244,21 @@ write-protected (so future writes will also result in a WP fault). These ioctls support a mode flag (``UFFDIO_COPY_MODE_WP`` or ``UFFDIO_CONTINUE_MODE_WP`` respectively) to configure the mapping this way. +Memory Poisioning Emulation +--------------------------- + +In response to a fault (either missing or minor), an action userspace can +take to "resolve" it is to issue a ``UFFDIO_POISON``. This will cause any +future faulters to either get a SIGBUS, or in KVM's case the guest will +receive an MCE as if there were hardware memory poisoning. + +This is used to emulate hardware memory poisoning. Imagine a VM running on a +machine which experiences a real hardware memory error. Later, we live migrate +the VM to another physical machine. Since we want the migration to be +transparent to the guest, we want that same address range to act as if it was +still poisoned, even though it's on a new physical host which ostentisbly +doesn't have a memory error in the exact same spot. + QEMU/KVM ========