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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 25338CE8D79 for ; Fri, 14 Nov 2025 19:00:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B1BB98E000F; Fri, 14 Nov 2025 14:00:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ACC6F8E0006; Fri, 14 Nov 2025 14:00:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F8B28E000F; Fri, 14 Nov 2025 14:00:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 7E28C8E0006 for ; Fri, 14 Nov 2025 14:00:13 -0500 (EST) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 4EBC44D254 for ; Fri, 14 Nov 2025 19:00:13 +0000 (UTC) X-FDA: 84110127906.12.6FCD80D Received: from mail-yx1-f50.google.com (mail-yx1-f50.google.com [74.125.224.50]) by imf29.hostedemail.com (Postfix) with ESMTP id 6B36F120014 for ; Fri, 14 Nov 2025 19:00:11 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=crjC2pRx; spf=pass (imf29.hostedemail.com: domain of pasha.tatashin@soleen.com designates 74.125.224.50 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=pass (policy=reject) header.from=soleen.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763146811; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Ihe0loas1LrTsn9bRuxuUBOFUFQUEsXdHcA1ZYhZ3IY=; b=e8Pta/JfWy7zKmovBWgE/dVJnsq/stKCM5MV4R223k71Zt5pi1f7VB43lRTXnRLx2KGNQw N2TkKRP4W8vVCos62xBV38waVMf3AdhE6y40OfTAwflqCZWGVQpn2Gfiu7YSABMUFbx/Nc 5YdLF0IyE0mTq+O9SKjRjegi2WJddF8= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=crjC2pRx; spf=pass (imf29.hostedemail.com: domain of pasha.tatashin@soleen.com designates 74.125.224.50 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=pass (policy=reject) header.from=soleen.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763146811; a=rsa-sha256; cv=none; b=AlT1Uj+VH9L+Wp9FGMwyTqSg4rI7fGIk5tlV1dIeH0SEd+OGHd+B9FOTBdVdC1xKV8OXYd +eXLmtRuXBOhj1wau8mIW0wwKFdCkHSNgYGScEd0JFg6AtMOEE6ytqfxR08LR7DZCAMA4i Jb7u/syzZ8ceo/9AoYk4QZslTvRF3fk= Received: by mail-yx1-f50.google.com with SMTP id 956f58d0204a3-63fc6115d65so2261990d50.0 for ; Fri, 14 Nov 2025 11:00:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1763146810; x=1763751610; darn=kvack.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:from:to:cc:subject:date:message-id :reply-to; bh=Ihe0loas1LrTsn9bRuxuUBOFUFQUEsXdHcA1ZYhZ3IY=; b=crjC2pRx6CMalFM49cJYnJfjOFzw8lWVZOGDZvn9XwbhBSrUmpsRinZY8PiyK8DUUV X4OYEQxDWnDpku95wNuDHbuQR2luMkDU04QwLbrmvKpgZqJncbvzP3TvR+xBDV0hwad1 +qP918/ITbOrUL/+ObVziE1lsQuq9YcYIoqcYwqnhEauQPjgUbNplNzzOROciuUEoc6Z KUp+uxU+w06qNkdR7moD03EJUxrduCcHUq2GJQa04EN5VkjSEAkOZBnUyWFtggfFxFSJ DEDR6VrGY7D1uJSjrIOrJ1dQ3a9An3gJgUZ0ZG5huGfYv6qvKV3CEmN2H9wgPE9PVDhW onWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763146810; x=1763751610; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=Ihe0loas1LrTsn9bRuxuUBOFUFQUEsXdHcA1ZYhZ3IY=; b=odhQnWLcBOMDeOU7ay0eHvIwDlC1J0Dh7BfLp6VULSSOssO0U4nXzsEHf3ZCJpfa/J 7DDVoMpCVJ4iqe/v1NhOZY9ja2tHYIxv/09cQSgat5PZRHW0P8NzCA/C/V2j0IejGH2/ RJ0wapp5MgmGKWO5ey3oEvp35QNTA0uy0y3/LqRiV8zhpWYLaQBYTvgpWiFxI4I432ND t6scDFVuoR/ZeHQOb84nqajDzNqnn1ySF8ks7sJd0nXu6KLe08OW6hJvv4FnVkcAQVVN rVzw/1WrJ2gwdehB16mcaQSaRgMq/2y7RotMegmFesunZD53GcG67kMc6LPf69ssr7OK p1Dw== X-Forwarded-Encrypted: i=1; AJvYcCVB6QPs6E/y8jzZn+4fJJZARVVraCJzC/B7EgJv1UDhCuu1K6w+7L/MGz+XjriQedLZjgZpdIdPPQ==@kvack.org X-Gm-Message-State: AOJu0YxlTUhNkxkn+CCVZtgwjM4Wa4rS8lPE1Bj6vFtkuhsNwRFfHcof 5JHRPlGO7Dhq1o+SWqNn6QaqJvbZbbdQbgY0quWwErOPgxcet6Mqh6PeWoLtFDXo9F8= X-Gm-Gg: ASbGncvAhYOi4zwUeSnnM+f4ztq3rLEiBDP0PogiRUVLzcz9L+XDCUFIjmJL/Ku1HO4 0BalGj0pu74kwQ8QVXlJSIvqAiE5XAAQuc1w+E/aideoEP/j1sBhu95kcGIbX9QN8u3RwTv/oPu wdtQOUrhS5dGDNrPvO99ui0eUrz6CX+MSGjbBHwzZu0E05HP96Xmh4jUrgv+Keqh82jUHNJl7Uh +0SP5ew3TIR4r+ISokVBPa07bG2nbxwTsnzt505rBMTRnrr1F5vZt3/QXuB9+eHWL73FMHaZ2S9 BvcUf6QaKbmmMPZCLudHUgDAuWAPorOY8WoR7WcIVuRPlMlxQqgcrIL30ehqfZGF1Mb7nWMbW4k 1P9hFbnDJyEp0OnJ+h+WAi2qa2By11No8yVF8J3B3DrNKoPu+BAkYtUlPktV2S5lqMPPKvQeUgZ 04clp4BDR8nr6kxTxaM3qKlXlYN1cMZad5+8NvlkYYrdqZPba461tyUPhP76jmvCMWZxb7XJoeB rRPKgg= X-Google-Smtp-Source: AGHT+IHtcsADCaRWmb9vZYl521slB2k1TyP9yi6kP/peGKq0p/n4sbxoK2XQz6YSUfgIDyLwv/pwEw== X-Received: by 2002:a05:690e:23c3:b0:636:563a:6725 with SMTP id 956f58d0204a3-641e7644cefmr2737299d50.49.1763146810418; Fri, 14 Nov 2025 11:00:10 -0800 (PST) Received: from soleen.c.googlers.com.com (182.221.85.34.bc.googleusercontent.com. [34.85.221.182]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-6410e8f4f2esm2014058d50.0.2025.11.14.11.00.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Nov 2025 11:00:10 -0800 (PST) From: Pasha Tatashin To: akpm@linux-foundation.org, bhe@redhat.com, pasha.tatashin@soleen.com, rppt@kernel.org, jasonmiu@google.com, arnd@arndb.de, coxu@redhat.com, dave@vasilevsky.ca, ebiggers@google.com, graf@amazon.com, kees@kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: [PATCH v2 03/13] kho: Introduce high-level memory allocation API Date: Fri, 14 Nov 2025 13:59:52 -0500 Message-ID: <20251114190002.3311679-4-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.52.0.rc1.455.g30608eb744-goog In-Reply-To: <20251114190002.3311679-1-pasha.tatashin@soleen.com> References: <20251114190002.3311679-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6B36F120014 X-Stat-Signature: aq843z8ky1fsaj9e4qsrrdatw56tknfi X-Rspam-User: X-HE-Tag: 1763146811-875216 X-HE-Meta: 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 PhEMnkEH nhLPmmxGgXT4hauVRsnLHUG8GwN9fYT46eHlP8YE33gVSJfsmyvhuY982iF/xr4N2zTsKNVJ4eq5y6eR/gnMoVpRr/Xgdaf8PcyHx6IJmXZLgP+BR+WXwPlk5Pnt2PAUygT/II8AAesdigARVPIHPqXWdPOBu9V/oRNpO1wbLBpkr8nxYb5JmVL5nTNO/YoDTudg4paevsSBfN5CxbtC867HqiVccMQCehfo0eaPCt4d3OUg0WqtG0gdf96SN2BQIt0d57w+y0r1yy2SVBgJkM2v2nzAZhKcGa85NqJYtbzhS21IWf4UOnzQMu2zxTZ/M7rPSYgNyZf/U5J6vLQqNX3ZMH9lQ7FM9z5FoPmq29gaNFqI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently, clients of KHO must manually allocate memory (e.g., via alloc_pages), calculate the page order, and explicitly call kho_preserve_folio(). Similarly, cleanup requires separate calls to unpreserve and free the memory. Introduce a high-level API to streamline this common pattern: - kho_alloc_preserve(size): Allocates physically contiguous, zeroed memory and immediately marks it for preservation. - kho_unpreserve_free(ptr): Unpreserves and frees the memory in the current kernel. - kho_restore_free(ptr): Restores the struct page state of preserved memory in the new kernel and immediately frees it to the page allocator. Signed-off-by: Pasha Tatashin Reviewed-by: Mike Rapoport (Microsoft) --- include/linux/kexec_handover.h | 22 +++++--- kernel/liveupdate/kexec_handover.c | 87 ++++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+), 7 deletions(-) diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h index 80ece4232617..38a9487a1a00 100644 --- a/include/linux/kexec_handover.h +++ b/include/linux/kexec_handover.h @@ -2,8 +2,9 @@ #ifndef LINUX_KEXEC_HANDOVER_H #define LINUX_KEXEC_HANDOVER_H -#include +#include #include +#include struct kho_scratch { phys_addr_t addr; @@ -48,6 +49,9 @@ int kho_preserve_pages(struct page *page, unsigned int nr_pages); int kho_unpreserve_pages(struct page *page, unsigned int nr_pages); int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation); int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation); +void *kho_alloc_preserve(size_t size); +void kho_unpreserve_free(void *mem); +void kho_restore_free(void *mem); struct folio *kho_restore_folio(phys_addr_t phys); struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages); void *kho_restore_vmalloc(const struct kho_vmalloc *preservation); @@ -101,6 +105,14 @@ static inline int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation) return -EOPNOTSUPP; } +void *kho_alloc_preserve(size_t size) +{ + return ERR_PTR(-EOPNOTSUPP); +} + +void kho_unpreserve_free(void *mem) { } +void kho_restore_free(void *mem) { } + static inline struct folio *kho_restore_folio(phys_addr_t phys) { return NULL; @@ -122,18 +134,14 @@ static inline int kho_add_subtree(const char *name, void *fdt) return -EOPNOTSUPP; } -static inline void kho_remove_subtree(void *fdt) -{ -} +static inline void kho_remove_subtree(void *fdt) { } static inline int kho_retrieve_subtree(const char *name, phys_addr_t *phys) { return -EOPNOTSUPP; } -static inline void kho_memory_init(void) -{ -} +static inline void kho_memory_init(void) { } static inline void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys, u64 scratch_len) diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index bc7f046a1313..5c5c9c46fe92 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -4,6 +4,7 @@ * Copyright (C) 2023 Alexander Graf * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport * Copyright (C) 2025 Google LLC, Changyuan Lyu + * Copyright (C) 2025 Pasha Tatashin */ #define pr_fmt(fmt) "KHO: " fmt @@ -1117,6 +1118,92 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation) } EXPORT_SYMBOL_GPL(kho_restore_vmalloc); +/** + * kho_alloc_preserve - Allocate, zero, and preserve memory. + * @size: The number of bytes to allocate. + * + * Allocates a physically contiguous block of zeroed pages that is large + * enough to hold @size bytes. The allocated memory is then registered with + * KHO for preservation across a kexec. + * + * Note: The actual allocated size will be rounded up to the nearest + * power-of-two page boundary. + * + * @return A virtual pointer to the allocated and preserved memory on success, + * or an ERR_PTR() encoded error on failure. + */ +void *kho_alloc_preserve(size_t size) +{ + struct folio *folio; + int order, ret; + + if (!size) + return ERR_PTR(-EINVAL); + + order = get_order(size); + if (order > MAX_PAGE_ORDER) + return ERR_PTR(-E2BIG); + + folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, order); + if (!folio) + return ERR_PTR(-ENOMEM); + + ret = kho_preserve_folio(folio); + if (ret) { + folio_put(folio); + return ERR_PTR(ret); + } + + return folio_address(folio); +} +EXPORT_SYMBOL_GPL(kho_alloc_preserve); + +/** + * kho_unpreserve_free - Unpreserve and free memory. + * @mem: Pointer to the memory allocated by kho_alloc_preserve(). + * + * Unregisters the memory from KHO preservation and frees the underlying + * pages back to the system. This function should be called to clean up + * memory allocated with kho_alloc_preserve(). + */ +void kho_unpreserve_free(void *mem) +{ + struct folio *folio; + + if (!mem) + return; + + folio = virt_to_folio(mem); + WARN_ON_ONCE(kho_unpreserve_folio(folio)); + folio_put(folio); +} +EXPORT_SYMBOL_GPL(kho_unpreserve_free); + +/** + * kho_restore_free - Restore and free memory after kexec. + * @mem: Pointer to the memory (in the new kernel's address space) + * that was allocated by the old kernel. + * + * This function is intended to be called in the new kernel (post-kexec) + * to take ownership of and free a memory region that was preserved by the + * old kernel using kho_alloc_preserve(). + * + * It first restores the pages from KHO (using their physical address) + * and then frees the pages back to the new kernel's page allocator. + */ +void kho_restore_free(void *mem) +{ + struct folio *folio; + + if (!mem) + return; + + folio = kho_restore_folio(__pa(mem)); + if (!WARN_ON(!folio)) + folio_put(folio); +} +EXPORT_SYMBOL_GPL(kho_restore_free); + static void __kho_abort(void) { if (kho_out.preserved_mem_map) { -- 2.52.0.rc1.455.g30608eb744-goog