riscv: handle superpage in pmap_enter_quick_locked()
Previously, if pmap_enter_l2() was asked to re-map an existing superpage (the result of madvise(MADV_WILLNEED) on a mapped range), it could 'fail' to do so, falling back to trying pmap_enter_quick_locked() for each 4K virtual page. Because this function does not check if the l2 entry it finds is a superpage, it would proceed, sometimes resulting in the creation of false PV entries. If the relevant range was later munmap'ed, the system would panic during the process' exit in pmap_remove_pages(), while attempting to clean up the PV entries for mappings which no longer exist. Instead, we should return early in the presence of an existing superpage, as is done in other pmaps. PR: 266108 Reviewed by: markj, alc MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D36563
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@ -3383,6 +3383,8 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
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* attempt fails, we don't retry. Instead, we give up.
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*/
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if (l2 != NULL && pmap_load(l2) != 0) {
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if ((pmap_load(l2) & PTE_RWX) != 0)
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return (NULL);
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phys = PTE_TO_PHYS(pmap_load(l2));
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mpte = PHYS_TO_VM_PAGE(phys);
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mpte->ref_count++;
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