xen: Do not pin/unpin PMD pages
i.e. with this simple test case: int fd = open("/dev/zero", O_RDONLY); munmap(mmap((void *)0x40000000, 0x1000_LEN, PROT_READ, MAP_PRIVATE, fd, 0), 0x1000); close(fd); we currently get: kernel BUG at arch/x86/xen/enlighten.c:678! ... EIP is at xen_release_pt+0x79/0xa9 ... Call Trace: [<c041da25>] ? __pmd_free_tlb+0x1a/0x75 [<c047a192>] ? free_pgd_range+0x1d2/0x2b5 [<c047a2f3>] ? free_pgtables+0x7e/0x93 [<c047b272>] ? unmap_region+0xb9/0xf5 [<c047c1bd>] ? do_munmap+0x193/0x1f5 [<c047c24f>] ? sys_munmap+0x30/0x3f [<c0408cce>] ? syscall_call+0x7/0xb ======================= and xen complains: (XEN) mm.c:2241:d4 Mfn 1cc37 not pinned Further details at: https://bugzilla.redhat.com/436453 Signed-off-by: Mark McLoughlin <markmc@redhat.com> Cc: xen-devel@lists.xensource.com Cc: Mark McLoughlin <markmc@redhat.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -689,8 +689,6 @@ static void xen_alloc_ptpage(struct mm_struct *mm, u32 pfn, unsigned level)
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make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
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if (level == PT_PTE)
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pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);
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else if (level == PT_PMD)
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pin_pagetable_pfn(MMUEXT_PIN_L2_TABLE, pfn);
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} else
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/* make sure there are no stray mappings of
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this page */
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@ -715,7 +713,8 @@ static void xen_release_ptpage(u32 pfn, unsigned level)
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if (PagePinned(page)) {
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if (!PageHighMem(page)) {
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pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn);
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if (level == PT_PTE)
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pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn);
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make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
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}
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}
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