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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 40070CD5BD0 for ; Thu, 28 May 2026 00:43:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XmiM0zp4RpwFxnSgF35nU0/vhB3kyRAcJWx3icQ9ch4=; b=st5aoKlG0kJZuiE7GdSsEwschj uLsf74neMTjwSJS0noH0JPzesqI32nAW7EIKKK8ndEC7y8ZZYha001cPCBv4soMMNt4eAN2BY2zZF TeDrISBZA3sXvVF4MLUWMq0rPHRAb31qP8yQ6mpCR4rhxK+UVvytZMgdLDAlq88CA9w0JXk7C2dgm +LPU6CfuzK94MAVLKSOC/63m4YBQ/wL5yWGhe2DtbMv1r3uTlDTEpCMoAn+soT3dGu/FZTkkbohqF gnAnQVGYVuNyvo0kn3nW6AUdMdSqqNed5DCOxH7H+H0W5jUcrfy+VkGGQO8eaCQYVyzNYqpk15nxF gNZvUYeA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wSOq5-00000004sr1-0Fgj; Thu, 28 May 2026 00:43:09 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wSOpU-00000004s53-1dzs; Thu, 28 May 2026 00:42:33 +0000 Received: by linux.microsoft.com (Postfix, from userid 1241) id 34DCB20B7179; Wed, 27 May 2026 17:42:21 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 34DCB20B7179 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1779928941; bh=XmiM0zp4RpwFxnSgF35nU0/vhB3kyRAcJWx3icQ9ch4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nT1WAQhYVhGyQcrpwbh+CUuDn4l7hSwQ+9uxGmhB3nC0ccpLqDneLzA5HOAC4gcP0 XE/P6+XloPaQe44ldBRelsVosfdKGOxFV4YKTqHcQyjrMNZBuBDzpNthSEaExCfyPe xuDZ/6yBo8hPaZmgKUYioRILvs5pkRdZegB9bmO0= From: Jork Loeser To: linux-hyperv@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org Cc: "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Alexander Graf , Jason Miu , Andrew Morton , David Hildenbrand , Muchun Song , Oscar Salvador , Baoquan He , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Kees Cook , Ran Xiaokai , Justinien Bouron , Sourabh Jain , Pingfan Liu , "Rafael J. Wysocki" , Mario Limonciello , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linux-kernel@vger.kernel.org, Michael Kelley , Jork Loeser Subject: [RFC PATCH 13/20] kho: add radix tree freeze and del_key() error reporting Date: Wed, 27 May 2026 17:41:55 -0700 Message-ID: <20260528004204.1484584-14-jloeser@linux.microsoft.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260528004204.1484584-1-jloeser@linux.microsoft.com> References: <20260528004204.1484584-1-jloeser@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260527_174232_458195_FAD892A7 X-CRM114-Status: GOOD ( 25.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add kho_radix_tree_freeze() to prevent further modifications to a KHO radix tree. After freezing, kho_radix_add_key() and kho_radix_del_key() return -EBUSY. This is used by the MSHV page preservation code to lock the tree before serializing it for kexec. Also change kho_radix_del_key() from void to int so it can report -EBUSY (frozen) and -ENOENT (key not present). Signed-off-by: Jork Loeser --- include/linux/kho_radix_tree.h | 24 ++++++++++---- kernel/liveupdate/kexec_handover.c | 51 +++++++++++++++++++++++------- 2 files changed, 57 insertions(+), 18 deletions(-) diff --git a/include/linux/kho_radix_tree.h b/include/linux/kho_radix_tree.h index c0840ecb230c..4fe2238e1e30 100644 --- a/include/linux/kho_radix_tree.h +++ b/include/linux/kho_radix_tree.h @@ -21,10 +21,10 @@ * scheme. Each key is an unsigned long that combines a page's physical * address and its order. * - * Client code is responsible for allocating the root node of the tree, - * initializing the mutex lock, and managing its lifecycle. It must use the - * tree data structures defined in the KHO ABI, - * `include/linux/kho/abi/kexec_handover.h`. + * Client code must initialize the tree using kho_radix_tree_init(). Pass + * a physical address to restore a tree preserved across kexec, or 0 to + * allocate a fresh empty tree. The tree uses data structures defined in + * the KHO ABI, `include/linux/kho/abi/kexec_handover.h`. */ struct kho_radix_node; @@ -32,6 +32,7 @@ struct kho_radix_node; struct kho_radix_tree { struct kho_radix_node *root; struct mutex lock; /* protects the tree's structure and root pointer */ + bool frozen; }; /** @@ -51,11 +52,12 @@ struct kho_radix_walk_cb { #ifdef CONFIG_KEXEC_HANDOVER int kho_radix_add_key(struct kho_radix_tree *tree, unsigned long key); -void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key); +int kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key); int kho_radix_walk_tree(struct kho_radix_tree *tree, const struct kho_radix_walk_cb *cb, void *data); int kho_radix_init_tree(struct kho_radix_tree *tree, struct kho_radix_node *root); void kho_radix_destroy_tree(struct kho_radix_tree *tree); +int kho_radix_tree_freeze(struct kho_radix_tree *tree); #else /* #ifdef CONFIG_KEXEC_HANDOVER */ @@ -64,8 +66,11 @@ static inline int kho_radix_add_key(struct kho_radix_tree *tree, unsigned long k return -EOPNOTSUPP; } -static inline void kho_radix_del_key(struct kho_radix_tree *tree, - unsigned long key) { } +static inline int kho_radix_del_key(struct kho_radix_tree *tree, + unsigned long key) +{ + return -EOPNOTSUPP; +} static inline int kho_radix_walk_tree(struct kho_radix_tree *tree, const struct kho_radix_walk_cb *cb, void *data) @@ -81,6 +86,11 @@ static inline int kho_radix_init_tree(struct kho_radix_tree *tree, static inline void kho_radix_destroy_tree(struct kho_radix_tree *tree) { } +static inline int kho_radix_tree_freeze(struct kho_radix_tree *tree) +{ + return -EOPNOTSUPP; +} + #endif /* #ifdef CONFIG_KEXEC_HANDOVER */ #endif /* _LINUX_KHO_RADIX_TREE_H */ diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 797ec285b698..2e2b4e73f00d 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -79,9 +79,6 @@ struct kho_out { static struct kho_out kho_out = { .lock = __MUTEX_INITIALIZER(kho_out.lock), - .radix_tree = { - .lock = __MUTEX_INITIALIZER(kho_out.radix_tree.lock), - }, }; struct kho_in { @@ -180,6 +177,28 @@ static void __ref kho_radix_free_node(struct kho_radix_node *node) memblock_free(node, PAGE_SIZE); } +/** + * kho_radix_tree_freeze - Freeze the tree, preventing further modifications. + * @tree: The KHO radix tree to freeze. + * + * After freezing, kho_radix_add_key() and kho_radix_del_key() will return + * -EBUSY. The check is performed under the tree's mutex, so there is no + * race between a concurrent add/del and the freeze. + * + * Return: 0 on success, -EBUSY if the tree is already frozen. + */ +int kho_radix_tree_freeze(struct kho_radix_tree *tree) +{ + guard(mutex)(&tree->lock); + + if (tree->frozen) + return -EBUSY; + + tree->frozen = true; + return 0; +} +EXPORT_SYMBOL_GPL(kho_radix_tree_freeze); + /** * kho_radix_add_key - Add a key to the radix tree. * @tree: The KHO radix tree. @@ -210,6 +229,9 @@ int kho_radix_add_key(struct kho_radix_tree *tree, unsigned long key) guard(mutex)(&tree->lock); + if (tree->frozen) + return -EBUSY; + /* Go from high levels to low levels */ for (i = KHO_TREE_MAX_DEPTH - 1; i > 0; i--) { idx = kho_radix_get_table_index(key, i); @@ -268,20 +290,26 @@ EXPORT_SYMBOL_GPL(kho_radix_add_key); * This function traverses the radix tree and clears the bit corresponding to * the key, effectively removing it from the tree. It does not free the tree's * intermediate nodes, even if they become empty. + * + * Return: 0 on success, -EINVAL if the tree is uninitialized, -EBUSY if + * frozen, -ENOENT if the key was not present. */ -void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key) +int kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key) { struct kho_radix_node *node = tree->root; struct kho_radix_leaf *leaf; unsigned int i, idx; if (WARN_ON_ONCE(!tree->root)) - return; + return -EINVAL; might_sleep(); guard(mutex)(&tree->lock); + if (WARN_ON_ONCE(tree->frozen)) + return -EBUSY; + /* Go from high levels to low levels */ for (i = KHO_TREE_MAX_DEPTH - 1; i > 0; i--) { idx = kho_radix_get_table_index(key, i); @@ -291,7 +319,7 @@ void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key) * return with a warning. */ if (WARN_ON(!node->table[idx])) - return; + return -ENOENT; node = phys_to_virt(node->table[idx]); } @@ -300,6 +328,8 @@ void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key) leaf = (struct kho_radix_leaf *)node; idx = kho_radix_get_bitmap_index(key); __clear_bit(idx, leaf->bitmap); + + return 0; } EXPORT_SYMBOL_GPL(kho_radix_del_key); @@ -346,6 +376,7 @@ int kho_radix_init_tree(struct kho_radix_tree *tree, struct kho_radix_node *root tree->root = root; mutex_init(&tree->lock); + tree->frozen = false; return 0; } EXPORT_SYMBOL_GPL(kho_radix_init_tree); @@ -1746,11 +1777,9 @@ static __init int kho_init(void) if (!kho_enable) return 0; - tree->root = kzalloc(PAGE_SIZE, GFP_KERNEL); - if (!tree->root) { - err = -ENOMEM; + err = kho_radix_init_tree(tree, NULL); + if (err) goto err_free_scratch; - } kho_out.fdt = kho_alloc_preserve(PAGE_SIZE); if (IS_ERR(kho_out.fdt)) { @@ -1807,7 +1836,7 @@ static __init int kho_init(void) err_free_fdt: kho_unpreserve_free(kho_out.fdt); err_free_kho_radix_tree_root: - kfree(tree->root); + free_page((unsigned long)tree->root); tree->root = NULL; err_free_scratch: kho_out.fdt = NULL; -- 2.43.0