From nobody Wed Dec 17 09:44:26 2025 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 7A305C00A98 for ; Fri, 20 Oct 2023 15:13:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377705AbjJTPNQ (ORCPT ); Fri, 20 Oct 2023 11:13:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377674AbjJTPNL (ORCPT ); Fri, 20 Oct 2023 11:13:11 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1EA0D79 for ; Fri, 20 Oct 2023 08:13:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1697814783; x=1729350783; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=FQt/ElawTffVXHEXsjLO8M8ZAD2Dp5CO9gICUmaNuMQ=; b=JwlV2vXMepybLmD1RTFGD6hjq0BkCEf2R5P7CfK6dONlApLTCPOSPOqE fPZen6ej1psU/SJyLsjR9Wp0XG3QlYNtDaIFbGhX/LRabHq8N0Z0g7mNW Eg7v8/D8ZL5+SDEBuXz8lSLPo3TPIiUsk2/snsKe3LGlEWn6RWPuMaKCO zrilSgKCmehK4eC38gWYZu4nUdaGQbI39v6ty23gcHtIlNVAiGo2fYKkO xc7D9x56LbQ9KQ3bDwshNT3LpDZ5CVCY8vzqYy7Q3a0yD+ZNVAGDIpqhm 2Uud2r0HNgN0r+rrjJKPNmVPlGAKHy8wuKpG50ECTZEyEor5XoHcibCd0 g==; X-IronPort-AV: E=McAfee;i="6600,9927,10869"; a="376893679" X-IronPort-AV: E=Sophos;i="6.03,239,1694761200"; d="scan'208";a="376893679" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2023 08:13:01 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10869"; a="761080289" X-IronPort-AV: E=Sophos;i="6.03,239,1694761200"; d="scan'208";a="761080289" Received: from dgutows1-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.249.39.237]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2023 08:12:56 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 3BB5B10A29A; Fri, 20 Oct 2023 18:12:45 +0300 (+03) From: "Kirill A. Shutemov" To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , "Kalra, Ashish" , Sean Christopherson , "Huang, Kai" , Baoquan He , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCHv2 08/13] x86/tdx: Account shared memory Date: Fri, 20 Oct 2023 18:12:37 +0300 Message-ID: <20231020151242.1814-9-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231020151242.1814-1-kirill.shutemov@linux.intel.com> References: <20231020151242.1814-1-kirill.shutemov@linux.intel.com> 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" The kernel will convert all shared memory back to private during kexec. The direct mapping page tables will provide information on which memory is shared. It is extremely important to convert all shared memory. If a page is missed, it will cause the second kernel to crash when it accesses it. Keep track of the number of shared pages. This will allow for cross-checking against the shared information in the direct mapping and reporting if the shared bit is lost. Include a debugfs interface that allows for the check to be performed at any point. Signed-off-by: Kirill A. Shutemov --- arch/x86/coco/tdx/tdx.c | 69 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 8897d3cc8a15..587bdeb88afa 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -5,6 +5,7 @@ #define pr_fmt(fmt) "tdx: " fmt =20 #include +#include #include #include #include @@ -37,6 +38,13 @@ =20 #define TDREPORT_SUBTYPE_0 0 =20 +static atomic_long_t nr_shared; + +static inline bool pte_decrypted(pte_t pte) +{ + return cc_mkdec(pte_val(pte)) =3D=3D pte_val(pte); +} + /* Called from __tdx_hypercall() for unrecoverable failure */ noinstr void __noreturn __tdx_hypercall_failed(void) { @@ -799,6 +807,11 @@ static int tdx_enc_status_change_finish(unsigned long = vaddr, int numpages, if (!enc && !tdx_enc_status_changed(vaddr, numpages, enc)) return -EIO; =20 + if (enc) + atomic_long_sub(numpages, &nr_shared); + else + atomic_long_add(numpages, &nr_shared); + return 0; } =20 @@ -874,3 +887,59 @@ void __init tdx_early_init(void) =20 pr_info("Guest detected\n"); } + +#ifdef CONFIG_DEBUG_FS +static int tdx_shared_memory_show(struct seq_file *m, void *p) +{ + unsigned long addr, end; + unsigned long found =3D 0; + + addr =3D PAGE_OFFSET; + end =3D PAGE_OFFSET + get_max_mapped(); + + while (addr < end) { + unsigned long size; + unsigned int level; + pte_t *pte; + + pte =3D lookup_address(addr, &level); + size =3D page_level_size(level); + + if (pte && pte_decrypted(*pte)) + found +=3D size / PAGE_SIZE; + + addr +=3D size; + + cond_resched(); + } + + seq_printf(m, "Number of unshared pages in kernel page tables: %16lu\n", + found); + seq_printf(m, "Number of pages accounted as unshared: %16ld\n", + atomic_long_read(&nr_shared)); + return 0; +} + +static int tdx_shared_memory_open(struct inode *inode, struct file *file) +{ + return single_open(file, tdx_shared_memory_show, NULL); +} + +static const struct file_operations tdx_shared_memory_fops =3D { + .open =3D tdx_shared_memory_open, + .read =3D seq_read, + .llseek =3D seq_lseek, + .release =3D single_release, +}; + +static __init int debug_tdx_shared_memory(void) +{ + if (!cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) + return 0; + + debugfs_create_file("tdx_shared_memory", S_IRUSR, arch_debugfs_dir, + NULL, &tdx_shared_memory_fops); + return 0; +} +fs_initcall(debug_tdx_shared_memory); +#endif --=20 2.41.0