From mboxrd@z Thu Jan 1 00:00:00 1970 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 6D516C433FE for ; Tue, 3 May 2022 17:50:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240711AbiECRxm (ORCPT ); Tue, 3 May 2022 13:53:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42838 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240674AbiECRxh (ORCPT ); Tue, 3 May 2022 13:53:37 -0400 Received: from mail-il1-x132.google.com (mail-il1-x132.google.com [IPv6:2607:f8b0:4864:20::132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC02C3B29F for ; Tue, 3 May 2022 10:50:04 -0700 (PDT) Received: by mail-il1-x132.google.com with SMTP id s14so4022219ild.6 for ; Tue, 03 May 2022 10:50:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digitalocean.com; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=gw+un10uJqUNP/SbL+e25B/lzjHm7kiGfOYsGY9F7XM=; b=IQ5l1Tw0QCU5PbCxVcnsc+tTDYVs0hkTHeCetz8NmOg+tc+WmC7hJ9Db1EH0ffn3vt lWg5GdxzYnone+VZISJSZcdXLdgw+/rkq0ScHAzuDlP8aaHL8YJrpDCusQSa2CwLTYVQ 5kiLmnnxp6CBthc47Q1I3FP1g2FAl3KmjJcy0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=gw+un10uJqUNP/SbL+e25B/lzjHm7kiGfOYsGY9F7XM=; b=pnE5Q3y2RiFUR8mrMZBiFXuM+fjLzM44tzgoVGS6NsWIUR9uVOED3An6eXI1ACLzG7 HTp4ZH3wRnRmVnR622jzrCmdMmlJ2wfubHklWbA58laDWyMISCJFaljW9UMBG/JnfH2y QZf6aYzbdOP5MJfUXH7vucF9nhWqZNGtRxnPIEi20dmh3LZ2rz6VPEAw4z+UEhOqX77E bu/LEvFmleMkHQjQY6s/JY8NL7a9dtJzSqjzP7utDyjJhRdqzL9qbr+sTSzOli5fkSOF rNSUzU3kJdJw0FqRuHz4G/gT5ltaG0WPfA6qblVwxlvVdGR1xkoGGZm1zOtqmnHlg6IJ zZgg== X-Gm-Message-State: AOAM532DzjW2BDqk/omGhs7aJALI3EE92gYD6tzhwgVYjsmoSZWLTPfg cRNHEXXKLS7alIrt5LnoiDUYAA== X-Google-Smtp-Source: ABdhPJzh+zb6aoHIl3yp5z+2hS5YP62Z1ngPLTw5+X3w+daEd6SSNy6hBReYVKdBs4/XoKgoLBqttA== X-Received: by 2002:a05:6e02:20e4:b0:2cc:4535:9d22 with SMTP id q4-20020a056e0220e400b002cc45359d22mr7443763ilv.195.1651600203864; Tue, 03 May 2022 10:50:03 -0700 (PDT) Received: from localhost ([2605:a601:ac0f:820:80d8:f53c:c84d:deaa]) by smtp.gmail.com with ESMTPSA id u6-20020a02aa86000000b0032b3a78176dsm4049997jai.49.2022.05.03.10.49.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 May 2022 10:49:48 -0700 (PDT) From: Seth Forshee To: Thomas Gleixner , Peter Zijlstra , Andy Lutomirski Cc: Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Paolo Bonzini , Sean Christopherson , linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, kvm@vger.kernel.org Subject: [PATCH v2] entry/kvm: Make vCPU tasks exit to userspace when a livepatch is pending Date: Tue, 3 May 2022 12:49:34 -0500 Message-Id: <20220503174934.2641605-1-sforshee@digitalocean.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org A task can be livepatched only when it is sleeping or it exits to userspace. This may happen infrequently for a heavily loaded vCPU task, leading to livepatch transition failures. Fake signals will be sent to tasks which fail patching via stack checking. This will cause running vCPU tasks to exit guest mode, but since no signal is pending they return to guest execution without exiting to userspace. Fix this by treating a pending livepatch migration like a pending signal, exiting to userspace with EINTR. This allows the task to be patched, and userspace should re-excecute KVM_RUN to resume guest execution. In my testing, systems where livepatching would timeout after 60 seconds were able to load livepatches within a couple of seconds with this change. Signed-off-by: Seth Forshee --- Changes in v2: - Added _TIF_SIGPENDING to XFER_TO_GUEST_MODE_WORK - Reworded commit message and comments to avoid confusion around the term "migrate" include/linux/entry-kvm.h | 4 ++-- kernel/entry/kvm.c | 7 ++++++- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h index 6813171afccb..bf79e4cbb5a2 100644 --- a/include/linux/entry-kvm.h +++ b/include/linux/entry-kvm.h @@ -17,8 +17,8 @@ #endif #define XFER_TO_GUEST_MODE_WORK \ - (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL | \ - _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK) + (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_PATCH_PENDING | \ + _TIF_NOTIFY_SIGNAL | _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK) struct kvm_vcpu; diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c index 9d09f489b60e..98439dfaa1a0 100644 --- a/kernel/entry/kvm.c +++ b/kernel/entry/kvm.c @@ -14,7 +14,12 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) task_work_run(); } - if (ti_work & _TIF_SIGPENDING) { + /* + * When a livepatch is pending, force an exit to userspace + * as though a signal is pending to allow the task to be + * patched. + */ + if (ti_work & (_TIF_SIGPENDING | _TIF_PATCH_PENDING)) { kvm_handle_signal_exit(vcpu); return -EINTR; } -- 2.32.0