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[192.55.52.88]) by mx.google.com with ESMTPS id x3-v6si1202539pfj.289.2018.06.26.07.22.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jun 2018 07:22:58 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of kirill.shutemov@linux.intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of kirill.shutemov@linux.intel.com designates 192.55.52.88 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 fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Jun 2018 07:22:58 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,274,1526367600"; d="scan'208";a="50032960" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga007.fm.intel.com with ESMTP; 26 Jun 2018 07:22:55 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id 3890A983; Tue, 26 Jun 2018 17:22:52 +0300 (EEST) From: "Kirill A. Shutemov" To: Ingo Molnar , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" , Tom Lendacky Cc: Dave Hansen , Kai Huang , Jacob Pan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" Subject: [PATCHv4 15/18] x86/mm: Calculate direct mapping size Date: Tue, 26 Jun 2018 17:22:42 +0300 Message-Id: <20180626142245.82850-16-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180626142245.82850-1-kirill.shutemov@linux.intel.com> References: <20180626142245.82850-1-kirill.shutemov@linux.intel.com> 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. Signed-off-by: Kirill A. Shutemov --- Documentation/x86/x86_64/mm.txt | 4 ++++ arch/x86/include/asm/page_64.h | 1 + arch/x86/include/asm/setup.h | 6 +++++ arch/x86/kernel/head64.c | 2 ++ arch/x86/kernel/setup.c | 3 +++ arch/x86/mm/init_64.c | 40 +++++++++++++++++++++++++++++++++ arch/x86/mm/kaslr.c | 11 ++++++--- 7 files changed, 64 insertions(+), 3 deletions(-) diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt index 5432a96d31ff..c5b92904090f 100644 --- a/Documentation/x86/x86_64/mm.txt +++ b/Documentation/x86/x86_64/mm.txt @@ -61,6 +61,10 @@ 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_64.h b/arch/x86/include/asm/page_64.h index 939b1cff4a7b..53c32af895ab 100644 --- a/arch/x86/include/asm/page_64.h +++ b/arch/x86/include/asm/page_64.h @@ -14,6 +14,7 @@ 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; 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 ae13bc974416..bcac5080cca5 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -59,6 +59,12 @@ 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 8047379e575a..854e8665aba0 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -59,6 +59,8 @@ 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); #define __head __section(.head.text) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 2f86d883dd95..09ddbd142e3c 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1053,6 +1053,9 @@ 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 a688617c727e..6fc506f33e58 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1399,6 +1399,46 @@ 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 systrem has? */ + direct_mapping_size = max_pfn << PAGE_SHIFT; + direct_mapping_size = round_up(direct_mapping_size, 1UL << 40); + + if (!IS_ENABLED(CONFIG_X86_INTEL_MKTME) || !mktme_nr_keyids) + goto out; + + /* + * 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 (direct_mapping_size > available_va) + direct_mapping_size = available_va; +} +#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 4408cd9a3bef..bf044ff50ec0 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -101,10 +101,15 @@ 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;