From nobody Tue Dec 30 14:56:25 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 05E3EC07548 for ; Wed, 15 Nov 2023 12:02:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343730AbjKOMCK (ORCPT ); Wed, 15 Nov 2023 07:02:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343713AbjKOMBd (ORCPT ); Wed, 15 Nov 2023 07:01:33 -0500 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6647E130 for ; Wed, 15 Nov 2023 04:01:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1700049689; x=1731585689; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=mn/ktomsmTvfB65J7SyJ0k/NJICrPsNe3CbwcOdaxtI=; b=Y0L7AgpqrBSjS6f0mtY8cqGC2N/c6L08BJogxaT5RQNvYYblnoGNOnwB P3NIvdfm6GUSQadjBNHo47Ec2Mhpewn30OyOQbpHK99XOn20hXPPBi4eJ 0D3d5U5Elkn4Yf0PtgoeCqe/+an0jlQKOjbbvSu2XgIQrMBjahkIDyR1D YN+HofW2uMBUUqdSCBcDwm2O4uy9ocpfTgJ61lQKRedjvJK6Q7AC+17DA w05tjRDPFMoCG79k0KuWG7eKw8UIGE1jGPZNI8B+tmll250J6UapVN/0Z fSgHmyXilGtzp7qrgoHysEIwMmg0bMrnynMjmKTpzGPEAlO88xyyJQm21 g==; X-IronPort-AV: E=McAfee;i="6600,9927,10894"; a="12411950" X-IronPort-AV: E=Sophos;i="6.03,304,1694761200"; d="scan'208";a="12411950" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Nov 2023 04:01:28 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.03,304,1694761200"; d="scan'208";a="6377705" Received: from mituomis-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.249.44.135]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Nov 2023 04:01:22 -0800 Received: by box.shutemov.name (Postfix, from userid 1000) id 9421310A31B; Wed, 15 Nov 2023 15:01:12 +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: [PATCHv3 09/14] x86/tdx: Account shared memory Date: Wed, 15 Nov 2023 15:00:39 +0300 Message-ID: <20231115120044.8034-10-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231115120044.8034-1-kirill.shutemov@linux.intel.com> References: <20231115120044.8034-1-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 2d90043a0e91..039f81b7c172 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) { @@ -820,6 +828,11 @@ 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 @@ -895,3 +908,59 @@ 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