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authorIan Campbell <ian.campbell@citrix.com>2010-11-03 15:32:21 +0000
committerJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2010-11-29 17:07:53 -0800
commit805e3f495057aa5307ad4e3d6dc7073d4733c691 (patch)
tree7d5bfeb30f5e178f05b932c20d64f2d9fd98583f /arch
parent31e323cca9d5c8afd372976c35a5d46192f540d1 (diff)
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xen: x86/32: perform initial startup on initial_page_table
Only make swapper_pg_dir readonly and pinned when generic x86 architecture code (which also starts on initial_page_table) switches to it. This helps ensure that the generic setup paths work on Xen unmodified. In particular clone_pgd_range writes directly to the destination pgd entries and is used to initialise swapper_pg_dir so we need to ensure that it remains writeable until the last possible moment during bring up. This is complicated slightly by the need to avoid sharing kernel PMD entries when running under Xen, therefore the Xen implementation must make a copy of the kernel PMD (which is otherwise referred to by both intial_page_table and swapper_pg_dir) before switching to swapper_pg_dir. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@linux.intel.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/xen/enlighten.c2
-rw-r--r--arch/x86/xen/mmu.c69
2 files changed, 56 insertions, 15 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 4a5973abefc..0db7303bccb 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1187,8 +1187,6 @@ asmlinkage void __init xen_start_kernel(void)
/* Allocate and initialize top and mid mfn levels for p2m structure */
xen_build_mfn_list_list();
- init_mm.pgd = pgd;
-
/* keep using Xen gdt for now; no urgent need to change it */
#ifdef CONFIG_X86_32
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 21ed8d7f75a..c9cf23e1744 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2119,44 +2119,83 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
return pgd;
}
#else /* !CONFIG_X86_64 */
-static RESERVE_BRK_ARRAY(pmd_t, level2_kernel_pgt, PTRS_PER_PMD);
+static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
+static RESERVE_BRK_ARRAY(pmd_t, swapper_kernel_pmd, PTRS_PER_PMD);
+
+static __init void xen_write_cr3_init(unsigned long cr3)
+{
+ unsigned long pfn = PFN_DOWN(__pa(swapper_pg_dir));
+
+ BUG_ON(read_cr3() != __pa(initial_page_table));
+ BUG_ON(cr3 != __pa(swapper_pg_dir));
+
+ /*
+ * We are switching to swapper_pg_dir for the first time (from
+ * initial_page_table) and therefore need to mark that page
+ * read-only and then pin it.
+ *
+ * Xen disallows sharing of kernel PMDs for PAE
+ * guests. Therefore we must copy the kernel PMD from
+ * initial_page_table into a new kernel PMD to be used in
+ * swapper_pg_dir.
+ */
+ swapper_kernel_pmd =
+ extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
+ memcpy(swapper_kernel_pmd, initial_kernel_pmd,
+ sizeof(pmd_t) * PTRS_PER_PMD);
+ swapper_pg_dir[KERNEL_PGD_BOUNDARY] =
+ __pgd(__pa(swapper_kernel_pmd) | _PAGE_PRESENT);
+ set_page_prot(swapper_kernel_pmd, PAGE_KERNEL_RO);
+
+ set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
+ xen_write_cr3(cr3);
+ pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, pfn);
+
+ pin_pagetable_pfn(MMUEXT_UNPIN_TABLE,
+ PFN_DOWN(__pa(initial_page_table)));
+ set_page_prot(initial_page_table, PAGE_KERNEL);
+ set_page_prot(initial_kernel_pmd, PAGE_KERNEL);
+
+ pv_mmu_ops.write_cr3 = &xen_write_cr3;
+}
__init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
unsigned long max_pfn)
{
pmd_t *kernel_pmd;
- level2_kernel_pgt = extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
+ initial_kernel_pmd =
+ extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->pt_base) +
xen_start_info->nr_pt_frames * PAGE_SIZE +
512*1024);
kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);
- memcpy(level2_kernel_pgt, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);
+ memcpy(initial_kernel_pmd, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);
- xen_map_identity_early(level2_kernel_pgt, max_pfn);
+ xen_map_identity_early(initial_kernel_pmd, max_pfn);
- memcpy(swapper_pg_dir, pgd, sizeof(pgd_t) * PTRS_PER_PGD);
- set_pgd(&swapper_pg_dir[KERNEL_PGD_BOUNDARY],
- __pgd(__pa(level2_kernel_pgt) | _PAGE_PRESENT));
+ memcpy(initial_page_table, pgd, sizeof(pgd_t) * PTRS_PER_PGD);
+ initial_page_table[KERNEL_PGD_BOUNDARY] =
+ __pgd(__pa(initial_kernel_pmd) | _PAGE_PRESENT);
- set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
- set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
+ set_page_prot(initial_kernel_pmd, PAGE_KERNEL_RO);
+ set_page_prot(initial_page_table, PAGE_KERNEL_RO);
set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
- xen_write_cr3(__pa(swapper_pg_dir));
-
- pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(swapper_pg_dir)));
+ pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE,
+ PFN_DOWN(__pa(initial_page_table)));
+ xen_write_cr3(__pa(initial_page_table));
memblock_x86_reserve_range(__pa(xen_start_info->pt_base),
__pa(xen_start_info->pt_base +
xen_start_info->nr_pt_frames * PAGE_SIZE),
"XEN PAGETABLES");
- return swapper_pg_dir;
+ return initial_page_table;
}
#endif /* CONFIG_X86_64 */
@@ -2290,7 +2329,11 @@ static const struct pv_mmu_ops xen_mmu_ops __initdata = {
.write_cr2 = xen_write_cr2,
.read_cr3 = xen_read_cr3,
+#ifdef CONFIG_X86_32
+ .write_cr3 = xen_write_cr3_init,
+#else
.write_cr3 = xen_write_cr3,
+#endif
.flush_tlb_user = xen_flush_tlb,
.flush_tlb_kernel = xen_flush_tlb,