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[192.55.52.93]) by mx.google.com with ESMTPS id y4si21166079pgv.154.2019.05.08.07.44.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 May 2019 07:44:45 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of kirill.shutemov@linux.intel.com designates 192.55.52.93 as permitted sender) client-ip=192.55.52.93; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of kirill.shutemov@linux.intel.com designates 192.55.52.93 as permitted sender) smtp.mailfrom=kirill.shutemov@linux.intel.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP; 08 May 2019 07:44:44 -0700 X-ExtLoop1: 1 Received: from black.fi.intel.com ([10.237.72.28]) by orsmga008.jf.intel.com with ESMTP; 08 May 2019 07:44:39 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id 8189A9B0; Wed, 8 May 2019 17:44:29 +0300 (EEST) From: "Kirill A. Shutemov" To: Andrew Morton , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , David Howells Cc: Kees Cook , Dave Hansen , Kai Huang , Jacob Pan , Alison Schofield , linux-mm@kvack.org, kvm@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCH, RFC 17/62] x86/mm: Calculate direct mapping size Date: Wed, 8 May 2019 17:43:37 +0300 Message-Id: <20190508144422.13171-18-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190508144422.13171-1-kirill.shutemov@linux.intel.com> References: <20190508144422.13171-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 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: X-Virus-Scanned: ClamAV using ClamSMTP The kernel needs to have a way to access encrypted memory. We have two option on how approach it: - Create temporary mappings every time kernel needs access to encrypted memory. That's basically brings highmem and its overhead back. - Create multiple direct mappings, one per-KeyID. In this setup we don't need to create temporary mappings on the fly -- encrypted memory is permanently available in kernel address space. We take the second approach as it has lower overhead. It's worth noting that with per-KeyID direct mappings compromised kernel would give access to decrypted data right away without additional tricks to get memory mapped with the correct KeyID. Per-KeyID mappings require a lot more virtual address space. On 4-level machine with 64 KeyIDs we max out 46-bit virtual address space dedicated for direct mapping with 1TiB of RAM. Given that we round up any calculation on direct mapping size to 1TiB, we effectively claim all 46-bit address space for direct mapping on such machine regardless of RAM size. Increased usage of virtual address space has implications for KASLR: we have less space for randomization. With 64 TiB claimed for direct mapping with 4-level we left with 27 TiB of entropy to place page_offset_base, vmalloc_base and vmemmap_base. 5-level paging provides much wider virtual address space and KASLR doesn't suffer significantly from per-KeyID direct mappings. It's preferred to run MKTME with 5-level paging. A direct mapping for each KeyID will be put next to each other in the virtual address space. We need to have a way to find boundaries of direct mapping for particular KeyID. The new variable direct_mapping_size specifies the size of direct mapping. With the value, it's trivial to find direct mapping for KeyID-N: PAGE_OFFSET + N * direct_mapping_size. Size of direct mapping is calculated during KASLR setup. If KALSR is disabled it happens during MKTME initialization. With MKTME size of direct mapping has to be power-of-2. It makes implementation of __pa() efficient. Signed-off-by: Kirill A. Shutemov --- Documentation/x86/x86_64/mm.txt | 4 +++ arch/x86/include/asm/page_32.h | 1 + arch/x86/include/asm/page_64.h | 2 ++ arch/x86/include/asm/setup.h | 6 ++++ arch/x86/kernel/head64.c | 4 +++ arch/x86/kernel/setup.c | 3 ++ arch/x86/mm/init_64.c | 58 +++++++++++++++++++++++++++++++++ arch/x86/mm/kaslr.c | 11 +++++-- 8 files changed, 86 insertions(+), 3 deletions(-) diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt index 804f9426ed17..81a1b96e0902 100644 --- a/Documentation/x86/x86_64/mm.txt +++ b/Documentation/x86/x86_64/mm.txt @@ -132,6 +132,10 @@ The direct mapping covers all memory in the system up to the highest memory address (this means in some cases it can also include PCI memory holes). +With MKTME, we have multiple direct mappings. One per-KeyID. They are put +next to each other. PAGE_OFFSET + N * direct_mapping_size can be used to +find direct mapping for KeyID-N. + vmalloc space is lazily synchronized into the different PML4/PML5 pages of the processes using the page fault handler, with init_top_pgt as reference. diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h index 94dbd51df58f..8bce788f9ca9 100644 --- a/arch/x86/include/asm/page_32.h +++ b/arch/x86/include/asm/page_32.h @@ -6,6 +6,7 @@ #ifndef __ASSEMBLY__ +#define direct_mapping_size 0 #define __phys_addr_nodebug(x) ((x) - PAGE_OFFSET) #ifdef CONFIG_DEBUG_VIRTUAL extern unsigned long __phys_addr(unsigned long); diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h index 939b1cff4a7b..f57fc3cc2246 100644 --- a/arch/x86/include/asm/page_64.h +++ b/arch/x86/include/asm/page_64.h @@ -14,6 +14,8 @@ extern unsigned long phys_base; extern unsigned long page_offset_base; extern unsigned long vmalloc_base; extern unsigned long vmemmap_base; +extern unsigned long direct_mapping_size; +extern unsigned long direct_mapping_mask; static inline unsigned long __phys_addr_nodebug(unsigned long x) { diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index ed8ec011a9fd..d2861074cf83 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -62,6 +62,12 @@ extern void x86_ce4100_early_setup(void); static inline void x86_ce4100_early_setup(void) { } #endif +#ifdef CONFIG_MEMORY_PHYSICAL_PADDING +void calculate_direct_mapping_size(void); +#else +static inline void calculate_direct_mapping_size(void) { } +#endif + #ifndef _SETUP #include diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 16b1cbd3a61e..c1a3ef88cb08 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -60,6 +60,10 @@ EXPORT_SYMBOL(vmalloc_base); unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4; EXPORT_SYMBOL(vmemmap_base); #endif +unsigned long direct_mapping_size __ro_after_init = -1UL; +EXPORT_SYMBOL(direct_mapping_size); +unsigned long direct_mapping_mask __ro_after_init = -1UL; +EXPORT_SYMBOL(direct_mapping_mask); #define __head __section(.head.text) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 3d872a527cd9..8b47e3e38926 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1057,6 +1057,9 @@ void __init setup_arch(char **cmdline_p) */ init_cache_modes(); + /* direct_mapping_size has to be initialized before KASLR and MKTME */ + calculate_direct_mapping_size(); + /* * Define random base addresses for memory sections after max_pfn is * defined and before each memory section base is used. diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index bccff68e3267..3a08d707eec8 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1383,6 +1383,64 @@ unsigned long memory_block_size_bytes(void) return memory_block_size_probed; } +#ifdef CONFIG_MEMORY_PHYSICAL_PADDING +void __init calculate_direct_mapping_size(void) +{ + unsigned long available_va; + + /* 1/4 of virtual address space is didicated for direct mapping */ + available_va = 1UL << (__VIRTUAL_MASK_SHIFT - 1); + + /* How much memory the system has? */ + direct_mapping_size = max_pfn << PAGE_SHIFT; + direct_mapping_size = round_up(direct_mapping_size, 1UL << 40); + + if (!mktme_nr_keyids) + goto out; + + /* + * For MKTME we need direct_mapping_size to be power-of-2. + * It makes __pa() implementation efficient. + */ + direct_mapping_size = roundup_pow_of_two(direct_mapping_size); + + /* + * Not enough virtual address space to address all physical memory with + * MKTME enabled. Even without padding. + * + * Disable MKTME instead. + */ + if (direct_mapping_size > available_va / (mktme_nr_keyids + 1)) { + pr_err("x86/mktme: Disabled. Not enough virtual address space\n"); + pr_err("x86/mktme: Consider switching to 5-level paging\n"); + mktme_disable(); + goto out; + } + + /* + * Virtual address space is divided between per-KeyID direct mappings. + */ + available_va /= mktme_nr_keyids + 1; +out: + /* Add padding, if there's enough virtual address space */ + direct_mapping_size += (1UL << 40) * CONFIG_MEMORY_PHYSICAL_PADDING; + if (mktme_nr_keyids) + direct_mapping_size = roundup_pow_of_two(direct_mapping_size); + + if (direct_mapping_size > available_va) + direct_mapping_size = available_va; + + /* + * For MKTME, make sure direct_mapping_size is still power-of-2 + * after adding padding and calculate mask that is used in __pa(). + */ + if (mktme_nr_keyids) { + direct_mapping_size = rounddown_pow_of_two(direct_mapping_size); + direct_mapping_mask = direct_mapping_size - 1; + } +} +#endif + #ifdef CONFIG_SPARSEMEM_VMEMMAP /* * Initialise the sparsemem vmemmap using huge-pages at the PMD level. diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 2228cc7d6b42..9cfba6627603 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -102,10 +102,15 @@ void __init kernel_randomize_memory(void) * add padding if needed (especially for memory hotplug support). */ BUG_ON(kaslr_regions[0].base != &page_offset_base); - memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + - CONFIG_MEMORY_PHYSICAL_PADDING; - /* Adapt phyiscal memory region size based on available memory */ + /* + * Calculate space required to map all physical memory. + * In case of MKTME, we map physical memory multiple times, one for + * each KeyID. If MKTME is disabled mktme_nr_keyids is 0. + */ + memory_tb = (direct_mapping_size * (mktme_nr_keyids + 1)) >> TB_SHIFT; + + /* Adapt physical memory region size based on available memory */ if (memory_tb < kaslr_regions[0].size_tb) kaslr_regions[0].size_tb = memory_tb;