forked from Mirrors/opensbi
6966ad0abe
This is achieved by removing the 'no-map' property from the 'reserved-memory' node when PMP is present, otherwise we keep it as it offers a small protection if the OS does not map this region at all. A new callback in platform_override is introduced and allows to fixup the device-tree. It is used here to override this new default behaviour on SiFive Fu540 platforms that has an erratum that prevents S-mode software to access a PMP protected region using 1GB page table mapping. If PMP is present, telling the OS not to map the reserved regions does not add much protection since it only avoids access to regions that are already protected by PMP. But by not allowing the OS to map those regions, it creates holes in the OS system memory map and prevents the use of hugepages which would generate, among other benefits, less TLB miss. Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> Reviewed-by: Atish Patra <atish.patra@wdc.com> Reviewed-by: Anup Patel <anup.patel@wdc.com>
48 lines
1.2 KiB
C
48 lines
1.2 KiB
C
/*
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2020 Western Digital Corporation or its affiliates.
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*
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* Authors:
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* Anup Patel <anup.patel@wdc.com>
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*/
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#include <platform_override.h>
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#include <sbi_utils/fdt/fdt_helper.h>
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#include <sbi_utils/fdt/fdt_fixup.h>
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static u64 sifive_fu540_tlbr_flush_limit(const struct fdt_match *match)
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{
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/*
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* The sfence.vma by virtual address does not work on
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* SiFive FU540 so we return remote TLB flush limit as zero.
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*/
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return 0;
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}
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static int sifive_fu540_fdt_fixup(void *fdt, const struct fdt_match *match)
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{
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/*
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* SiFive Freedom U540 has an erratum that prevents S-mode software
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* to access a PMP protected region using 1GB page table mapping, so
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* always add the no-map attribute on this platform.
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*/
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fdt_reserved_memory_nomap_fixup(fdt);
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return 0;
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}
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static const struct fdt_match sifive_fu540_match[] = {
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{ .compatible = "sifive,fu540" },
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{ .compatible = "sifive,fu540g" },
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{ .compatible = "sifive,fu540-c000" },
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{ .compatible = "sifive,hifive-unleashed-a00" },
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{ },
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};
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const struct platform_override sifive_fu540 = {
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.match_table = sifive_fu540_match,
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.tlbr_flush_limit = sifive_fu540_tlbr_flush_limit,
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.fdt_fixup = sifive_fu540_fdt_fixup,
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};
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