This patch series brings 52-bit kernel VA support to arm64; if supported at boot time. A new kernel option CONFIG_ARM64_VA_BITS_48_52 is available when configured with a 64KB PAGE_SIZE (as on ARMv8.2-LPA, 52-bit VAs are only allowed when running with a 64KB granule). Switching between 48 and 52-bit does not involve any changes to the number of page table levels. The number of PGDIR entries increases when running with a 52 bit kernel VA. In order to allow the kernel to switch between VA spaces at boot time, we need to re-arrange the current kernel VA space. If we place the kernel at the bottom of the address space, then symbol addresses will be independent of address space size. (We can't assume relocation will be enabled). The new kernel VA space looks like this (running with 48/52-bit kernel VA): 0xffff000000000000/0xfff0000000000000 ttbr1 start - linear mapping start 0xffff800000000000/0xfff8000000000000 midpoint of address space 0xffff800000000000/0xfffda00000000000 KASAN start 0xffffa00000000000/0xffffa00000000000 vmalloc start --- 0xfffffbdfd67b0000 vmemmap start 0xfffffbffd6800000 Fixed map start 0xffffffffd6c00000 PCI IO start 0xffffffffd7e00000 kernel modules start 0xffffffffdfe00000 kernel image start 0xffffffffffe00000 guard region for PTR_ERR The KASAN end address is the same for both 48 and 52 bit kernel VA spaces, meaning that KASAN "grows upwards" into the extra VA space available when running with 52-bit. This allows us to run with inline KASAN, where the offset is baked into the code in many places, on both VA spaces using the same binary. In order to allow for this logic, the KASAN_SHADOW_OFFSET logic was altered to match the system used for x86; namely that KASAN_SHADOW_OFFSET is a Kconfig constant rather than a derived quantity. In order to simplify future VA work, the code to compute the KASAN shadow offset is supplied as a script in the documentation folder. If KASAN is not enabled, then the VMALLOC start position is variable depending on VA_BITS. Thus VMALLOC_START cannot always be considered constant. This patch series modifies VA_BITS from a constant pre-processor macro, to a runtime variable and this requires changes to other parts of the arm64 code such the page table dumper. Some parts of the code require pre-processing constants derived from VA_BITS, so two new pre-processor constants have been introduced: VA_BITS_MIN the minimum number of VA_BITS used, this can be used to bound addresses conservatively s.t. mappings work for both address space sizes. An example use case being the EFI stub code efi_get_max_initrd_addr(). Another example being to determine whether or not we need an extra page table level for the identity mapping (on 64KB PAGE_SIZE we already have 3-levels for both 48-bit and 52-bit VA space). VA_BITS_ALT if running with a higher kernel VA space, this is the number of bits available. VA_BITS_MIN and VA_BITS_ALT can be used together to generate constants (or test compile time asserts) which are then chosen at runtime. I am mindful how disruptive the change to VA_BITS is, but I have so far been unable to simplify this further. One idea I had was to remove VA_BITS completely but that just makes the seris a lot more complicated. Another idea was to fix VA_BITS to either 48 or 52, this doesn't really help things. Either choice breaks derived addresses and also, less obviously, breaks the meaning behind the constant. efi_get_max_initrd_addr will give the wrong results if we choose 52 for example. Though disruptive, having VA_BITS de-constified will help us pick out bugs at compile time that one may not otherwise notice if it is set to the wrong constant. That said, I'm receptive to any ideas that can simplify this. One can't assume that ARMv8.2-LPA implies ARMv8.1-VHE, so changes are also made to the KVM HYP mapping code to support both 48 and 52-bit VAs. In writing the support, I unearthed some subtle bugs in the KVM HYP mapping logic and these are addressed in the first two patches of this series. This patch series applies to 4.15-rc2, and the early pagetable patches I posted earlier: http://lists.infradead.org/pipermail/linux-arm-kernel/2017-November/543494.html Steve Capper (12): KVM: arm/arm64: vgic: Remove spurious call to kern_hyp_va arm64: KVM: Enforce injective kern_hyp_va mappings arm/arm64: KVM: Formalise end of direct linear map arm64: Initialise high_memory global variable earlier arm64: mm: Remove VMALLOC checks from update_mapping_prot(.) arm64: mm: Flip kernel VA space arm64: mm: Place kImage at bottom of VA space arm64: kasan: Switch to using KASAN_SHADOW_OFFSET arm64: dump: Make kernel page table dumper dynamic again arm64: mm: Make VA_BITS variable, introduce VA_BITS_MIN arm64: KVM: Add support for an alternative VA space arm64: mm: Add 48/52-bit kernel VA support Documentation/arm64/kasan-offsets.sh | 17 ++++++++ arch/arm/include/asm/kvm_hyp.h | 2 + arch/arm/include/asm/memory.h | 1 + arch/arm64/Kconfig | 22 ++++++++++ arch/arm64/Makefile | 7 --- arch/arm64/include/asm/assembler.h | 2 +- arch/arm64/include/asm/cpucaps.h | 6 ++- arch/arm64/include/asm/efi.h | 4 +- arch/arm64/include/asm/kasan.h | 24 +++++------ arch/arm64/include/asm/kvm_hyp.h | 10 +++++ arch/arm64/include/asm/kvm_mmu.h | 83 ++++++++++++++++++++++++++++-------- arch/arm64/include/asm/memory.h | 42 +++++++++++------- arch/arm64/include/asm/mmu_context.h | 2 +- arch/arm64/include/asm/pgtable.h | 13 ++++-- arch/arm64/include/asm/processor.h | 2 +- arch/arm64/kernel/cpufeature.c | 47 +++++++++++++++++--- arch/arm64/kernel/head.S | 13 +++--- arch/arm64/kvm/hyp-init.S | 2 +- arch/arm64/mm/dump.c | 59 ++++++++++++++++++++----- arch/arm64/mm/fault.c | 2 +- arch/arm64/mm/init.c | 16 +++---- arch/arm64/mm/kasan_init.c | 14 +++--- arch/arm64/mm/mmu.c | 11 ++--- arch/arm64/mm/proc.S | 42 +++++++++++++++++- virt/kvm/arm/hyp/vgic-v2-sr.c | 4 +- virt/kvm/arm/mmu.c | 4 +- 26 files changed, 336 insertions(+), 115 deletions(-) create mode 100644 Documentation/arm64/kasan-offsets.sh -- 2.11.0 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
