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The RISC-V port requires that kernel PGD entries are to be synchronized between MMs. This is done via the vmalloc_fault() function, that simply copies the PGD entries from init_mm to the faulting one. Historically, faulting in PGD entries have been a source for both bugs [1], and poor performance. One way to get rid of vmalloc faults is by pre-allocating the PGD entries. Pre-allocating the entries potientially wastes 64 * 4K (65 on SV39). The pre-allocation function is pulled from Jörg Rödel's x86 work, with the addition of 3-level page tables (PMD allocations). The pmd_alloc() function needs the ptlock cache to be initialized (when split page locks is enabled), so the pre-allocation is done in a RISC-V specific pgtable_cache_init() implementation. Pre-allocate the kernel PGD entries for the vmalloc/modules area, but only for 64b platforms. Link: https://lore.kernel.org/lkml/20200508144043.13893-1-joro@8bytes.org/ # [1] Signed-off-by: Björn Töpel <bjorn@rivosinc.com> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com> Link: https://lore.kernel.org/r/20230531093817.665799-1-bjorn@kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> |
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| boot | ||
| configs | ||
| errata | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mm | ||
| net | ||
| purgatory | ||
| tools | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.debug | ||
| Kconfig.errata | ||
| Kconfig.socs | ||
| Makefile | ||
| Makefile.postlink | ||