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| author | Christoph Hellwig <hch@lst.de> | 2019-10-28 13:10:41 +0100 |
|---|---|---|
| committer | Paul Walmsley <paul.walmsley@sifive.com> | 2019-11-18 00:17:39 +0100 |
| commit | 6bd33e1ece528f67646db33bf97406b747dafda0 (patch) | |
| tree | f78c5001071a475fa5bed9781c07a609118684f7 /arch/riscv/include/asm/tlbflush.h | |
| parent | riscv: clear the instruction cache and all registers when booting (diff) | |
| download | linux-6bd33e1ece528f67646db33bf97406b747dafda0.tar.xz linux-6bd33e1ece528f67646db33bf97406b747dafda0.zip | |
riscv: add nommu support
The kernel runs in M-mode without using page tables, and thus can't run
bare metal without help from additional firmware.
Most of the patch is just stubbing out code not needed without page
tables, but there is an interesting detail in the signals implementation:
- The normal RISC-V syscall ABI only implements rt_sigreturn as VDSO
entry point, but the ELF VDSO is not supported for nommu Linux.
We instead copy the code to call the syscall onto the stack.
In addition to enabling the nommu code a new defconfig for a small
kernel image that can run in nommu mode on qemu is also provided, to run
a kernel in qemu you can use the following command line:
qemu-system-riscv64 -smp 2 -m 64 -machine virt -nographic \
-kernel arch/riscv/boot/loader \
-drive file=rootfs.ext2,format=raw,id=hd0 \
-device virtio-blk-device,drive=hd0
Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anup Patel <anup@brainfault.org>
[paul.walmsley@sifive.com: updated to apply; add CONFIG_MMU guards
around PCI_IOBASE definition to fix build issues; fixed checkpatch
issues; move the PCI_IO_* and VMEMMAP address space macros along
with the others; resolve sparse warning]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Diffstat (limited to 'arch/riscv/include/asm/tlbflush.h')
| -rw-r--r-- | arch/riscv/include/asm/tlbflush.h | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h index f02188a5b0f4..394cfbccdcd9 100644 --- a/arch/riscv/include/asm/tlbflush.h +++ b/arch/riscv/include/asm/tlbflush.h @@ -10,6 +10,7 @@ #include <linux/mm_types.h> #include <asm/smp.h> +#ifdef CONFIG_MMU static inline void local_flush_tlb_all(void) { __asm__ __volatile__ ("sfence.vma" : : : "memory"); @@ -20,14 +21,19 @@ static inline void local_flush_tlb_page(unsigned long addr) { __asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"); } +#else /* CONFIG_MMU */ +#define local_flush_tlb_all() do { } while (0) +#define local_flush_tlb_page(addr) do { } while (0) +#endif /* CONFIG_MMU */ -#ifdef CONFIG_SMP +#if defined(CONFIG_SMP) && defined(CONFIG_MMU) void flush_tlb_all(void); void flush_tlb_mm(struct mm_struct *mm); void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr); void flush_tlb_range(struct vm_area_struct *vma, unsigned long start, unsigned long end); -#else /* CONFIG_SMP */ +#else /* CONFIG_SMP && CONFIG_MMU */ + #define flush_tlb_all() local_flush_tlb_all() #define flush_tlb_page(vma, addr) local_flush_tlb_page(addr) @@ -38,7 +44,7 @@ static inline void flush_tlb_range(struct vm_area_struct *vma, } #define flush_tlb_mm(mm) flush_tlb_all() -#endif /* CONFIG_SMP */ +#endif /* !CONFIG_SMP || !CONFIG_MMU */ /* Flush a range of kernel pages */ static inline void flush_tlb_kernel_range(unsigned long start, |