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([94.75.70.14]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54504fc26b3sm1409118e87.44.2025.02.12.08.50.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Feb 2025 08:50:19 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 71e6e335-e961-11ef-b3ef-695165c68f79 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1739379020; x=1739983820; darn=lists.xenproject.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=w6Ju1c/EKr8BS6g8kPT3M1roaRELu8awq2bLgFaPOzY=; b=mtW3D7lkN7xnrc5XqJlDn94EbwxIcItWg8ejQ9lhA9cE4nKqM/h4DdU0ze+sCj3nNL 0vgo3H65W+D9zWg77mgN6xM6ucI2UpkOBxW1nobXirFH2OtzFwZFObQdjFGOCX7jkU5n jfv1SWOg9Ri5jLAy18X+r6d+h2NFcNV4C4Hl8km1B+PKUAwNSoXIZCqKaPxO1I5/wqDJ B8CXsOD/yACD1PzJ0LSqCiWUbnGj3cb3nLMtzWCxb/gwZnZTNln3EqtCDUIp4o40gDU2 w5lgRPV28eafnsKE1nawTkwQph4YPXkJaBb0ru2tfhZDYFBH09/aehxF6mKZUhJC1FEK bG1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739379020; x=1739983820; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=w6Ju1c/EKr8BS6g8kPT3M1roaRELu8awq2bLgFaPOzY=; b=Z6wzx8DlGh/TByXUm+WeDflOobugE/q9xfFSNCUv50XSUDTF/iCkSyjX6pDhbxddf5 cDVga1Khf5rZZ0fAZ+OU7o+60FSix+vyAIj3QAW9hNN8k7CMmVZUZeUplb61bc7K7noA nhK+pAfH3RBiO/qBh+sE3wVHMju0qlUa/rqRJtrViZi8jSVoyWLAWgRa0MPEsALS+cu5 FQQs/t5abIRrxtfXyZ8Tud3TK80+GIQP+v7M5wRn93EbM0a6EyNgL8HIS/6XvOxxDjnA ghYRC62ZKS/vwnZ0LNeNwiW1wtVMlXer/dLZt/O3gMYBop/T+6Dur3t9d+uKN87hWVLq NrZA== X-Gm-Message-State: AOJu0YzGC4vlUqUNgVmJ9PEBe8Wa7UkpUBwasiZECd1hacQtaALzRt0C ajO7v4f0kiP+T4K5uM9L5Pj0Pvd+0UdsoMrcjQbNxm30ab+WQdh4BO6iBA== X-Gm-Gg: ASbGncvrXDyuAkG1Jnyh7xsgZC8E7HyYyhNV7qA80fWdkilXxB3BHXig6CnTCtylCJ/ YJtlJpBYFUBMBKCd0Af5ASwKnUpvyb9T3VfNM+8Q8/qBJJT5Ux4eHZyhnBXO7vmzWpYN9vqOY0I AvhgWOqqtZgQVz/dXab6SrYhkRZAbTqK7hP6qliclfJ/ZWSBZ9e2clL5XrhQjUQD9iBhz91GqgK K60DZCuPChAaN9zUNNULnNMnTv+E8U965ZgjrQ2Ju21odDClafv148dcWzE3mBIOqHWr6XAh6T6 5nfNFdTDc3V2KlkQ X-Google-Smtp-Source: AGHT+IF49H77zg0gqFLnPXN29InT0mAjlfxNZqmf8Rjnu9yg4fuqcu0t8647RlM+JI6hTu6BbC3b+A== X-Received: by 2002:a05:6512:2247:b0:545:1098:88db with SMTP id 2adb3069b0e04-545180ea954mr1122217e87.11.1739379019478; Wed, 12 Feb 2025 08:50:19 -0800 (PST) From: Oleksii Kurochko To: xen-devel@lists.xenproject.org Cc: Oleksii Kurochko , Alistair Francis , Bob Eshleman , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , Jan Beulich , Julien Grall , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini Subject: [PATCH for 4.20? v4 3/3] xen/riscv: update mfn calculation in pt_mapping_level() Date: Wed, 12 Feb 2025 17:50:13 +0100 Message-ID: <38093d9843afbba9dda7326ee6e8cc3c99343cf6.1739363240.git.oleksii.kurochko@gmail.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: References: MIME-Version: 1.0 When pt_update() is called with arguments (..., INVALID_MFN, ..., 0 or 1), it indicates that a mapping is being destroyed/modifyed. In the case when modifying or destroying a mapping, it is necessary to search until a leaf node is found, instead of searching for a page table entry based on the precalculated `level` and `order`(look at pt_update()). This is because when `mfn` == INVALID_MFN, the `mask` (in pt_mapping_level()) will take into account only `vfn`, which could accidentally return an incorrect level, leading to the discovery of an incorrect page table entry. For example, if `vfn` is page table level 1 aligned, but it was mapped as page table level 0, then pt_mapping_level() will return `level` = 1, since only `vfn` (which is page table level 1 aligned) is taken into account when `mfn` == INVALID_MFN (look at pt_mapping_level()). Fixes: c2f1ded524 ("xen/riscv: page table handling") Signed-off-by: Oleksii Kurochko --- Changes in v4: - Move defintion of local variable table inside `else` case as it is used only there. - Change unmap_table(table) to unmap_table(entry) for unifying both cases when _pt_walk() is used and when pte is seached on the specified level. - Initialize local variable `entry` to avoid compilation error caused by uninitialized variable. --- Changes in v3: - Drop ASSERT() for order as it isn't needed anymore. - Drop PTE_LEAF_SEARCH and use instead level=CONFIG_PAGING_LEVELS; refactor connected code correspondingly. - Calculate order once. - Drop initializer for local variable order. - Drop BUG_ON(!pte_is_mapping(*entry)) for the case when leaf searching happens as there is a similar check in pt_check_entry(). Look at pt.c:41 and pt.c:75. --- Changes in v2: - Introduce PTE_LEAF_SEARCH to tell page table update operation to walk down to wherever the leaf entry is. - Use introduced PTE_LEAF_SEARCH to not searching pte_t entry twice. - Update the commit message. --- xen/arch/riscv/pt.c | 97 +++++++++++++++++++++++++++++---------------- 1 file changed, 63 insertions(+), 34 deletions(-) diff --git a/xen/arch/riscv/pt.c b/xen/arch/riscv/pt.c index 260a3a9699..ed0587d58b 100644 --- a/xen/arch/riscv/pt.c +++ b/xen/arch/riscv/pt.c @@ -249,12 +249,10 @@ pte_t pt_walk(vaddr_t va, unsigned int *pte_level) /* Update an entry at the level @target. */ static int pt_update_entry(mfn_t root, vaddr_t virt, - mfn_t mfn, unsigned int target, + mfn_t mfn, unsigned int *target, unsigned int flags) { int rc; - unsigned int level = HYP_PT_ROOT_LEVEL; - pte_t *table; /* * The intermediate page table shouldn't be allocated when MFN isn't * valid and we are not populating page table. @@ -265,41 +263,48 @@ static int pt_update_entry(mfn_t root, vaddr_t virt, * combinations of (mfn, flags). */ bool alloc_tbl = !mfn_eq(mfn, INVALID_MFN) || (flags & PTE_POPULATE); - pte_t pte, *entry; - - /* convenience aliases */ - DECLARE_OFFSETS(offsets, virt); + pte_t pte, *entry = NULL; - table = map_table(root); - for ( ; level > target; level-- ) + if ( *target == CONFIG_PAGING_LEVELS ) + entry = _pt_walk(virt, target); + else { - rc = pt_next_level(alloc_tbl, &table, offsets[level]); - if ( rc == XEN_TABLE_MAP_NOMEM ) + pte_t *table; + unsigned int level = HYP_PT_ROOT_LEVEL; + /* convenience aliases */ + DECLARE_OFFSETS(offsets, virt); + + table = map_table(root); + for ( ; level > *target; level-- ) { - rc = -ENOMEM; - goto out; + rc = pt_next_level(alloc_tbl, &table, offsets[level]); + if ( rc == XEN_TABLE_MAP_NOMEM ) + { + rc = -ENOMEM; + goto out; + } + + if ( rc == XEN_TABLE_MAP_NONE ) + { + rc = 0; + goto out; + } + + if ( rc != XEN_TABLE_NORMAL ) + break; } - if ( rc == XEN_TABLE_MAP_NONE ) + if ( level != *target ) { - rc = 0; + dprintk(XENLOG_ERR, + "%s: Shattering superpage is not supported\n", __func__); + rc = -EOPNOTSUPP; goto out; } - if ( rc != XEN_TABLE_NORMAL ) - break; - } - - if ( level != target ) - { - dprintk(XENLOG_ERR, - "%s: Shattering superpage is not supported\n", __func__); - rc = -EOPNOTSUPP; - goto out; + entry = table + offsets[level]; } - entry = table + offsets[level]; - rc = -EINVAL; if ( !pt_check_entry(*entry, mfn, flags) ) goto out; @@ -331,7 +336,8 @@ static int pt_update_entry(mfn_t root, vaddr_t virt, rc = 0; out: - unmap_table(table); + if ( entry ) + unmap_table(entry); return rc; } @@ -424,17 +430,40 @@ static int pt_update(vaddr_t virt, mfn_t mfn, while ( left ) { - unsigned int order, level; - - level = pt_mapping_level(vfn, mfn, left, flags); - order = XEN_PT_LEVEL_ORDER(level); + unsigned int order, level = CONFIG_PAGING_LEVELS; - ASSERT(left >= BIT(order, UL)); + /* + * In the case when modifying or destroying a mapping, it is necessary + * to search until a leaf node is found, instead of searching for + * a page table entry based on the precalculated `level` and `order` + * (look at pt_update()). + * This is because when `mfn` == INVALID_MFN, the `mask`(in + * pt_mapping_level()) will take into account only `vfn`, which could + * accidentally return an incorrect level, leading to the discovery of + * an incorrect page table entry. + * + * For example, if `vfn` is page table level 1 aligned, but it was + * mapped as page table level 0, then pt_mapping_level() will return + * `level` = 1, since only `vfn` (which is page table level 1 aligned) + * is taken into account when `mfn` == INVALID_MFN + * (look at pt_mapping_level()). + * + * To force searching until a leaf node is found is necessary to have + * `level` == CONFIG_PAGING_LEVELS which is a default value for + * `level`. + * + * For other cases (when a mapping is not being modified or destroyed), + * pt_mapping_level() should be used. + */ + if ( !mfn_eq(mfn, INVALID_MFN) || (flags & PTE_POPULATE) ) + level = pt_mapping_level(vfn, mfn, left, flags); - rc = pt_update_entry(root, vfn << PAGE_SHIFT, mfn, level, flags); + rc = pt_update_entry(root, vfn << PAGE_SHIFT, mfn, &level, flags); if ( rc ) break; + order = XEN_PT_LEVEL_ORDER(level); + vfn += 1UL << order; if ( !mfn_eq(mfn, INVALID_MFN) ) mfn = mfn_add(mfn, 1UL << order);