Re: [RFC PATCH 00/12] Introduce sv48 support without relocable kernel
On Sat, 30 Jan 2021 01:33:20 PST (-0800), a...@ghiti.fr wrote: Hi Palmer, On 1/4/21 2:58 PM, Alexandre Ghiti wrote: This patchset, contrary to the previous versions, allows to have a single kernel for sv39 and sv48 without being relocatable. The idea comes from Arnd Bergmann who suggested to do the same as x86, that is mapping the kernel to the end of the address space, which allows the kernel to be linked at the same address for both sv39 and sv48 and then does not require to be relocated at runtime. This is an RFC because I need to at least rebase a few commits and add documentation. The most interesting patches where I expect feedbacks are 1/12, 2/12 and 8/12. Note that moving the kernel out of the linear mapping and sv48 support can be separate patchsets, I share them together today to show that it works (this patchset is rebased on top of v5.10). If we agree about the overall idea, I'll rebase my relocatable patchset on top of that and then KASLR implementation from Zong will be greatly simplified since moving the kernel out of the linear mapping will avoid to copy the kernel physically. This implements sv48 support at runtime. The kernel will try to boot with 4-level page table and will fallback to 3-level if the HW does not support it. Folding the 4th level into a 3-level page table has almost no cost at runtime. Finally, the user can now ask for sv39 explicitly by using the device-tree which will reduce memory footprint and reduce the number of memory accesses in case of TLB miss. Alexandre Ghiti (12): riscv: Move kernel mapping outside of linear mapping riscv: Protect the kernel linear mapping riscv: Get rid of compile time logic with MAX_EARLY_MAPPING_SIZE riscv: Allow to dynamically define VA_BITS riscv: Simplify MAXPHYSMEM config riscv: Prepare ptdump for vm layout dynamic addresses asm-generic: Prepare for riscv use of pud_alloc_one and pud_free riscv: Implement sv48 support riscv: Allow user to downgrade to sv39 when hw supports sv48 riscv: Use pgtable_l4_enabled to output mmu type in cpuinfo riscv: Explicit comment about user virtual address space size riscv: Improve virtual kernel memory layout dump arch/riscv/Kconfig | 34 +-- arch/riscv/boot/loader.lds.S| 3 +- arch/riscv/include/asm/csr.h| 3 +- arch/riscv/include/asm/fixmap.h | 3 + arch/riscv/include/asm/page.h | 33 ++- arch/riscv/include/asm/pgalloc.h| 40 +++ arch/riscv/include/asm/pgtable-64.h | 104 ++- arch/riscv/include/asm/pgtable.h| 68 +++-- arch/riscv/include/asm/sparsemem.h | 6 +- arch/riscv/kernel/cpu.c | 23 +- arch/riscv/kernel/head.S| 6 +- arch/riscv/kernel/module.c | 4 +- arch/riscv/kernel/vmlinux.lds.S | 3 +- arch/riscv/mm/context.c | 2 +- arch/riscv/mm/init.c| 376 arch/riscv/mm/physaddr.c| 2 +- arch/riscv/mm/ptdump.c | 56 +++- drivers/firmware/efi/libstub/efi-stub.c | 2 +- include/asm-generic/pgalloc.h | 24 +- include/linux/sizes.h | 3 +- 20 files changed, 648 insertions(+), 147 deletions(-) Any thought about the idea ? Is it going in the right direction ? I have fixed quite a few things since I posted this so don't bother giving this patchset a full review. My only real issue was the relocation stuff, which appears to be fixed. I haven't had the time to look at the patches, but it wouldn't hurt to send another revision. The best bet might be to just wait until 5.11 and send on top of that, it's too late for this one anyway and that'll be a stable base to test from.
Re: [RFC PATCH 00/12] Introduce sv48 support without relocable kernel
Hi Palmer, On 1/4/21 2:58 PM, Alexandre Ghiti wrote: This patchset, contrary to the previous versions, allows to have a single kernel for sv39 and sv48 without being relocatable. The idea comes from Arnd Bergmann who suggested to do the same as x86, that is mapping the kernel to the end of the address space, which allows the kernel to be linked at the same address for both sv39 and sv48 and then does not require to be relocated at runtime. This is an RFC because I need to at least rebase a few commits and add documentation. The most interesting patches where I expect feedbacks are 1/12, 2/12 and 8/12. Note that moving the kernel out of the linear mapping and sv48 support can be separate patchsets, I share them together today to show that it works (this patchset is rebased on top of v5.10). If we agree about the overall idea, I'll rebase my relocatable patchset on top of that and then KASLR implementation from Zong will be greatly simplified since moving the kernel out of the linear mapping will avoid to copy the kernel physically. This implements sv48 support at runtime. The kernel will try to boot with 4-level page table and will fallback to 3-level if the HW does not support it. Folding the 4th level into a 3-level page table has almost no cost at runtime. Finally, the user can now ask for sv39 explicitly by using the device-tree which will reduce memory footprint and reduce the number of memory accesses in case of TLB miss. Alexandre Ghiti (12): riscv: Move kernel mapping outside of linear mapping riscv: Protect the kernel linear mapping riscv: Get rid of compile time logic with MAX_EARLY_MAPPING_SIZE riscv: Allow to dynamically define VA_BITS riscv: Simplify MAXPHYSMEM config riscv: Prepare ptdump for vm layout dynamic addresses asm-generic: Prepare for riscv use of pud_alloc_one and pud_free riscv: Implement sv48 support riscv: Allow user to downgrade to sv39 when hw supports sv48 riscv: Use pgtable_l4_enabled to output mmu type in cpuinfo riscv: Explicit comment about user virtual address space size riscv: Improve virtual kernel memory layout dump arch/riscv/Kconfig | 34 +-- arch/riscv/boot/loader.lds.S| 3 +- arch/riscv/include/asm/csr.h| 3 +- arch/riscv/include/asm/fixmap.h | 3 + arch/riscv/include/asm/page.h | 33 ++- arch/riscv/include/asm/pgalloc.h| 40 +++ arch/riscv/include/asm/pgtable-64.h | 104 ++- arch/riscv/include/asm/pgtable.h| 68 +++-- arch/riscv/include/asm/sparsemem.h | 6 +- arch/riscv/kernel/cpu.c | 23 +- arch/riscv/kernel/head.S| 6 +- arch/riscv/kernel/module.c | 4 +- arch/riscv/kernel/vmlinux.lds.S | 3 +- arch/riscv/mm/context.c | 2 +- arch/riscv/mm/init.c| 376 arch/riscv/mm/physaddr.c| 2 +- arch/riscv/mm/ptdump.c | 56 +++- drivers/firmware/efi/libstub/efi-stub.c | 2 +- include/asm-generic/pgalloc.h | 24 +- include/linux/sizes.h | 3 +- 20 files changed, 648 insertions(+), 147 deletions(-) Any thought about the idea ? Is it going in the right direction ? I have fixed quite a few things since I posted this so don't bother giving this patchset a full review. Thanks, Alex
[RFC PATCH 00/12] Introduce sv48 support without relocable kernel
This patchset, contrary to the previous versions, allows to have a single kernel for sv39 and sv48 without being relocatable. The idea comes from Arnd Bergmann who suggested to do the same as x86, that is mapping the kernel to the end of the address space, which allows the kernel to be linked at the same address for both sv39 and sv48 and then does not require to be relocated at runtime. This is an RFC because I need to at least rebase a few commits and add documentation. The most interesting patches where I expect feedbacks are 1/12, 2/12 and 8/12. Note that moving the kernel out of the linear mapping and sv48 support can be separate patchsets, I share them together today to show that it works (this patchset is rebased on top of v5.10). If we agree about the overall idea, I'll rebase my relocatable patchset on top of that and then KASLR implementation from Zong will be greatly simplified since moving the kernel out of the linear mapping will avoid to copy the kernel physically. This implements sv48 support at runtime. The kernel will try to boot with 4-level page table and will fallback to 3-level if the HW does not support it. Folding the 4th level into a 3-level page table has almost no cost at runtime. Finally, the user can now ask for sv39 explicitly by using the device-tree which will reduce memory footprint and reduce the number of memory accesses in case of TLB miss. Alexandre Ghiti (12): riscv: Move kernel mapping outside of linear mapping riscv: Protect the kernel linear mapping riscv: Get rid of compile time logic with MAX_EARLY_MAPPING_SIZE riscv: Allow to dynamically define VA_BITS riscv: Simplify MAXPHYSMEM config riscv: Prepare ptdump for vm layout dynamic addresses asm-generic: Prepare for riscv use of pud_alloc_one and pud_free riscv: Implement sv48 support riscv: Allow user to downgrade to sv39 when hw supports sv48 riscv: Use pgtable_l4_enabled to output mmu type in cpuinfo riscv: Explicit comment about user virtual address space size riscv: Improve virtual kernel memory layout dump arch/riscv/Kconfig | 34 +-- arch/riscv/boot/loader.lds.S| 3 +- arch/riscv/include/asm/csr.h| 3 +- arch/riscv/include/asm/fixmap.h | 3 + arch/riscv/include/asm/page.h | 33 ++- arch/riscv/include/asm/pgalloc.h| 40 +++ arch/riscv/include/asm/pgtable-64.h | 104 ++- arch/riscv/include/asm/pgtable.h| 68 +++-- arch/riscv/include/asm/sparsemem.h | 6 +- arch/riscv/kernel/cpu.c | 23 +- arch/riscv/kernel/head.S| 6 +- arch/riscv/kernel/module.c | 4 +- arch/riscv/kernel/vmlinux.lds.S | 3 +- arch/riscv/mm/context.c | 2 +- arch/riscv/mm/init.c| 376 arch/riscv/mm/physaddr.c| 2 +- arch/riscv/mm/ptdump.c | 56 +++- drivers/firmware/efi/libstub/efi-stub.c | 2 +- include/asm-generic/pgalloc.h | 24 +- include/linux/sizes.h | 3 +- 20 files changed, 648 insertions(+), 147 deletions(-) -- 2.20.1
