forked from Mirrors/opensbi
platform/lib: Allow the OS to map the regions that are protected by PMP
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>
This commit is contained in:

committed by
Anup Patel

parent
e2c3f01af4
commit
6966ad0abe
@@ -70,7 +70,7 @@ void fdt_plic_fixup(void *fdt, const char *compat)
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static int fdt_resv_memory_update_node(void *fdt, unsigned long addr,
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unsigned long size, int index,
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int parent)
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int parent, bool no_map)
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{
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int na = fdt_address_cells(fdt, 0);
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int ns = fdt_size_cells(fdt, 0);
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@@ -99,14 +99,16 @@ static int fdt_resv_memory_update_node(void *fdt, unsigned long addr,
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if (subnode < 0)
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return subnode;
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/*
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* Tell operating system not to create a virtual
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* mapping of the region as part of its standard
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* mapping of system memory.
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*/
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err = fdt_setprop_empty(fdt, subnode, "no-map");
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if (err < 0)
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return err;
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if (no_map) {
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/*
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* Tell operating system not to create a virtual
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* mapping of the region as part of its standard
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* mapping of system memory.
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*/
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err = fdt_setprop_empty(fdt, subnode, "no-map");
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if (err < 0)
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return err;
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}
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/* encode the <reg> property value */
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val = reg;
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@@ -199,7 +201,8 @@ int fdt_reserved_memory_fixup(void *fdt)
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*/
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addr = scratch->fw_start & ~(scratch->fw_size - 1UL);
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size = (1UL << log2roundup(scratch->fw_size));
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return fdt_resv_memory_update_node(fdt, addr, size, 0, parent);
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return fdt_resv_memory_update_node(fdt, addr, size,
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0, parent, true);
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}
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for (i = 0, j = 0; i < sbi_hart_pmp_count(scratch); i++) {
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@@ -211,13 +214,37 @@ int fdt_reserved_memory_fixup(void *fdt)
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if (prot & (PMP_R | PMP_W | PMP_X))
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continue;
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fdt_resv_memory_update_node(fdt, addr, size, j, parent);
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fdt_resv_memory_update_node(fdt, addr, size, j, parent, false);
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j++;
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}
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return 0;
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}
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int fdt_reserved_memory_nomap_fixup(void *fdt)
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{
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int parent, subnode;
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int err;
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/* Locate the reserved memory node */
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parent = fdt_path_offset(fdt, "/reserved-memory");
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if (parent < 0)
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return parent;
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fdt_for_each_subnode(subnode, fdt, parent) {
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/*
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* Tell operating system not to create a virtual
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* mapping of the region as part of its standard
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* mapping of system memory.
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*/
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err = fdt_setprop_empty(fdt, subnode, "no-map");
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if (err < 0)
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return err;
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}
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return 0;
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}
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void fdt_fixups(void *fdt)
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{
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fdt_plic_fixup(fdt, "riscv,plic0");
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