From nobody Sun Feb 8 14:30:43 2026 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 3A10DC4332F for ; Mon, 12 Dec 2022 17:06:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231817AbiLLRGm (ORCPT ); Mon, 12 Dec 2022 12:06:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232848AbiLLRGS (ORCPT ); Mon, 12 Dec 2022 12:06:18 -0500 Received: from esa2.hc3370-68.iphmx.com (esa2.hc3370-68.iphmx.com [216.71.145.153]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 386D926E4 for ; Mon, 12 Dec 2022 09:06:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1670864777; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=sMPzjY9YCDiCSf18nv+XYdrNotL4tPcjoEGZ13RJQys=; b=EJm/AeVbjpUAPNTcydgPeRlpOp6LmePfkaepbQ8z5BEM6DGoyZgF21x6 4yzRZX3tj1b37gmjymERE6py6Iph+a8ugYuyf54+VBvQYHeYQaq8zqr6t Vu2g/074JEkft0yojXFp0KVxF3W3ivaIa3WTHifJ/uwJkN7+/aH+By0tt g=; Authentication-Results: esa2.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none X-SBRS: 4.0 X-MesageID: 87954350 X-Ironport-Server: esa2.hc3370-68.iphmx.com X-Remote-IP: 162.221.156.83 X-Policy: $RELAYED IronPort-Data: A9a23:rm/1iKBo8za6zBVW//7jw5YqxClBgxIJ4kV8jS/XYbTApGx33mNSz jQaWWiDa/aNZzT9KIh3aI/g/RxT75+DzNZmQQY4rX1jcSlH+JHPbTi7wuUcHAvJd5GeExg3h yk6QoOdRCzhZiaE/n9BCpC48T8nk/nNHuCnYAL9EngZbRd+Tys8gg5Ulec8g4p56fC0GArIs t7pyyHlEAbNNwVcbyRFtcpvlDs15K6o4WlB5ARkDRx2lAS2e0c9Xcp3yZ6ZdxMUcqEMdsamS uDKyq2O/2+x13/B3fv8z94X2mVTKlLjFVDmZkh+AsBOsTAbzsAG6Y4pNeJ0VKtio27hc+ada jl6ncfYpQ8BZsUgkQmGOvVSO3kW0aZuoNcrLZUj2CA6IoKvn3bEmp1T4E8K0YIw0eRRIUhgp PsiBTlVVkGPpPnu8Ym+Vbw57igjBJGD0II3v3hhyXfSDOo8QICFSKLPjTNa9G5u3IYUR6+YP pdHL2o0BPjDS0Qn1lM/MJ8k2s2pgmLyWzZZtEiUtew85G27IAlZgOe8bYaOJ4TiqcN9mHyyl H7/wk/FMhhdCfC2yWre0W29mbqa9c/8cN1LT+DpnhJwu3WI3XAaAhASUVq9oNG6h1S4VtYZL FYbkgIpqaUx70WtQsPKQwyjoHWEsxgfXPJdC+Q/rgqKz8L88wufQ2QJUDNFQNgnr9MtAywn0 EeTmNHkDiApt6eaIVqZ97GJvXaxNDITIGsqeyAJV00G7sPlrYV1iQjAJv5hH7SylcbdAizrz naBqy1WulkIpZdVjePhpwmB2m/y4MiSJuIo2unJdkmnyCNQSt+iXaGhsWCK4dVbdLeiS0bU6 RDohPOixOwJCJiMkgmET+MMAKyl6p65DdHMvbJ8N8J/rmrwohZPaagVuWgjfxkxbq7obBezO CfuVRVtCIi/1ZdARYt+eMqPBssj1sAM/vy1B6mPPrKijnWcHTJrHR2Ch2bKhAgBc2B2y8nT3 Kt3lu7yZUv28Yw9kFKLqx41iNfHPBwWy2LJXozcxB+6y7eYb3P9Ye5bbwPRPrtksvPf8FS9H zNj2yyikkU3bQEDSnOPrd57wa4ichDX+qwaW+QIL7Xec2KK6UkqCuPLwKNJRmCWt/09qws8x VnkAhUw4AOm1RX6xfCiNigLhEXHAcwu8hrW/EUEYT6V5pTUSdz/tPtOK8VsI+hPGS4K5accc sTpsv6oWpxnIgkrMRxHBXUhhOSOrCiWuD8= IronPort-HdrOrdr: A9a23:FB7TDqp+xM8KxmKDlMMcfy0aV5rzeYIsimQD101hICG9JPbo8f xGUs516faUskdzZJhOo7u90cW7K080lqQU3WByB9mftVLdyQyVxehZhOPfKlvbdhEWndQ96U 4PScRDIey1N1Rgksbx7C6/DZINxNGG9YqshevY0h5WPGVXgw4L1XYBNu42eHcGITWvpPACZf ih2vY= X-IronPort-AV: E=Sophos;i="5.96,239,1665460800"; d="scan'208";a="87954350" From: Per Bilse To: CC: Per Bilse , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , "moderated list:XEN HYPERVISOR INTERFACE" Subject: [PATCH v2] drivers/xen/hypervisor: Expose Xen SIF flags to userspace Date: Mon, 12 Dec 2022 17:06:05 +0000 Message-ID: <20221212170605.28192-1-per.bilse@citrix.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" /proc/xen is a legacy pseudo filesystem which predates Xen support getting merged into Linux. It has largely been replaced with more normal locations for data (/sys/hypervisor/ for info, /dev/xen/ for user devices). We want to compile xenfs support out of the dom0 kernel. There is one item which only exists in /proc/xen, namely /proc/xen/capabilities with "control_d" being the signal of "you're in the control domain". This ultimately comes from the SIF flags provided at VM start. This patch exposes all SIF flags in /sys/hypervisor/start_flags/ as boolean files, one for each bit, returning '1' if set, '0' otherwise. Two known flags, 'privileged' and 'initdomain', are explicitly named, and all remaining flags can be accessed via generically named files, as suggested by Andrew Cooper. Signed-off-by: Per Bilse --- v2: minor fix to layout, incorporate suggestions from Juergen Gross --- Documentation/ABI/stable/sysfs-hypervisor-xen | 13 ++++ drivers/xen/sys-hypervisor.c | 69 +++++++++++++++++-- 2 files changed, 78 insertions(+), 4 deletions(-) diff --git a/Documentation/ABI/stable/sysfs-hypervisor-xen b/Documentation/= ABI/stable/sysfs-hypervisor-xen index 748593c64568..dbc5eccce8ea 100644 --- a/Documentation/ABI/stable/sysfs-hypervisor-xen +++ b/Documentation/ABI/stable/sysfs-hypervisor-xen @@ -120,3 +120,16 @@ Contact: xen-devel@lists.xenproject.org Description: If running under Xen: The Xen version is in the format . This is the part of it. + +What: /sys/hypervisor/start_flags/* +Date: December 2022 +KernelVersion: 6.1.0 +Contact: xen-devel@lists.xenproject.org +Description: If running under Xen: + All bits in Xen's start-flags are represented as + boolean files, returning '1' if set, '0' otherwise. + This takes the place of the defunct /proc/xen/capabilities, + which would contain "control_d" on dom0, and be empty + otherwise. This flag is now exposed as "initdomain" in + addition to the "privileged" flag; all other possible flags + are accessible as "unknownXX". diff --git a/drivers/xen/sys-hypervisor.c b/drivers/xen/sys-hypervisor.c index fcb0792f090e..f5460b34ae6f 100644 --- a/drivers/xen/sys-hypervisor.c +++ b/drivers/xen/sys-hypervisor.c @@ -31,7 +31,10 @@ struct hyp_sysfs_attr { struct attribute attr; ssize_t (*show)(struct hyp_sysfs_attr *, char *); ssize_t (*store)(struct hyp_sysfs_attr *, const char *, size_t); - void *hyp_attr_data; + union { + void *hyp_attr_data; + unsigned long hyp_attr_value; + }; }; =20 static ssize_t type_show(struct hyp_sysfs_attr *attr, char *buffer) @@ -399,6 +402,60 @@ static int __init xen_sysfs_properties_init(void) return sysfs_create_group(hypervisor_kobj, &xen_properties_group); } =20 +#define FLAG_UNAME "unknown" +#define FLAG_UNAME_FMT FLAG_UNAME "%02u" +#define FLAG_UNAME_MAX sizeof(FLAG_UNAME "XX") +#define FLAG_COUNT (sizeof(xen_start_flags) * BITS_PER_BYTE) +static_assert(sizeof(xen_start_flags)=20 + <=3D sizeof_field(struct hyp_sysfs_attr, hyp_attr_value)); + +static ssize_t flag_show(struct hyp_sysfs_attr *attr, char *buffer) +{ + char *p =3D buffer; + + *p++ =3D '0' + ((xen_start_flags & attr->hyp_attr_value) !=3D 0); + *p++ =3D '\n'; + return p - buffer;=20 +} + +#define FLAG_NODE(flag, node) \ + [ilog2(flag)] =3D { \ + .attr =3D { .name =3D #node, .mode =3D 0444 },\ + .show =3D flag_show, \ + .hyp_attr_value =3D flag \ + } + +/* + * Add new, known flags here. No other changes are required, but + * note that each known flag wastes one entry in flag_unames[]. + * The code/complexity machinations to avoid this isn't worth it + * for a few entries, but keep it in mind. + */ +static struct hyp_sysfs_attr flag_attrs[FLAG_COUNT] =3D { + FLAG_NODE(SIF_PRIVILEGED, privileged), + FLAG_NODE(SIF_INITDOMAIN, initdomain) +}; +static struct attribute_group xen_flags_group =3D { + .name =3D "start_flags", + .attrs =3D (struct attribute *[FLAG_COUNT + 1]){} +}; +static char flag_unames[FLAG_COUNT][FLAG_UNAME_MAX]; + +static int __init xen_sysfs_flags_init(void) +{ + for (unsigned fnum =3D 0; fnum !=3D FLAG_COUNT; fnum++) { + if (likely(flag_attrs[fnum].attr.name =3D=3D NULL)) { + sprintf(flag_unames[fnum], FLAG_UNAME_FMT, fnum); + flag_attrs[fnum].attr.name =3D flag_unames[fnum]; + flag_attrs[fnum].attr.mode =3D 0444; + flag_attrs[fnum].show =3D flag_show; + flag_attrs[fnum].hyp_attr_value =3D 1 << fnum; + } + xen_flags_group.attrs[fnum] =3D &flag_attrs[fnum].attr; + } + return sysfs_create_group(hypervisor_kobj, &xen_flags_group); +} + #ifdef CONFIG_XEN_HAVE_VPMU struct pmu_mode { const char *name; @@ -539,18 +596,22 @@ static int __init hyper_sysfs_init(void) ret =3D xen_sysfs_properties_init(); if (ret) goto prop_out; + ret =3D xen_sysfs_flags_init(); + if (ret) + goto flags_out; #ifdef CONFIG_XEN_HAVE_VPMU if (xen_initial_domain()) { ret =3D xen_sysfs_pmu_init(); if (ret) { - sysfs_remove_group(hypervisor_kobj, - &xen_properties_group); - goto prop_out; + sysfs_remove_group(hypervisor_kobj, &xen_flags_group); + goto flags_out; } } #endif goto out; =20 +flags_out: + sysfs_remove_group(hypervisor_kobj, &xen_properties_group); prop_out: sysfs_remove_file(hypervisor_kobj, &uuid_attr.attr); uuid_out: --=20 2.31.1