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Subject[PATCH 30 of 55] xen64: map an initial chunk of physical memory
Date
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Early in boot, map a chunk of extra physical memory for use later on.
We need a pool of mapped pages to allocate further pages to construct
pagetables mapping all physical memory.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/xen/enlighten.c | 79 ++++++++++++++++++++++++++++++++++++++++------
1 file changed, 69 insertions(+), 10 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1382,6 +1382,61 @@
}

/*
+ * Identity map, in addition to plain kernel map. This needs to be
+ * large enough to allocate page table pages to allocate the rest.
+ * Each page can map 2MB.
+ */
+static pte_t level1_ident_pgt[PTRS_PER_PTE * 4] __page_aligned_bss;
+
+static __init void xen_map_identity_early(unsigned long max_pfn)
+{
+ unsigned pmdidx, pteidx;
+ unsigned ident_pte;
+ unsigned long pfn;
+
+ ident_pte = 0;
+ pfn = 0;
+ for(pmdidx = 0; pmdidx < PTRS_PER_PMD && pfn < max_pfn; pmdidx++) {
+ pte_t *pte_page;
+
+ BUG_ON(level2_ident_pgt[pmdidx].pmd != level2_kernel_pgt[pmdidx].pmd);
+
+ /* Reuse or allocate a page of ptes */
+ if (pmd_present(level2_ident_pgt[pmdidx]))
+ pte_page = m2v(level2_ident_pgt[pmdidx].pmd);
+ else {
+ /* Check for free pte pages */
+ if (ident_pte == ARRAY_SIZE(level1_ident_pgt))
+ break;
+
+ pte_page = &level1_ident_pgt[ident_pte];
+ ident_pte += PTRS_PER_PTE;
+
+ /* Install new l1 in l2(s) */
+ level2_ident_pgt[pmdidx] = __pmd(__pa(pte_page) | _PAGE_TABLE);
+ level2_kernel_pgt[pmdidx] = level2_ident_pgt[pmdidx];
+ }
+
+ /* Install mappings */
+ for(pteidx = 0; pteidx < PTRS_PER_PTE; pteidx++, pfn++) {
+ pte_t pte;
+
+ if (pfn > max_pfn_mapped)
+ max_pfn_mapped = pfn;
+
+ if (!pte_none(pte_page[pteidx]))
+ continue;
+
+ pte = pfn_pte(pfn, PAGE_KERNEL_EXEC);
+ pte_page[pteidx] = pte;
+ }
+ }
+
+ for(pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
+ set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);
+}
+
+/*
* Set up the inital kernel pagetable.
*
* We can construct this by grafting the Xen provided pagetable into
@@ -1392,7 +1447,7 @@
* of the physical mapping once some sort of allocator has been set
* up.
*/
-static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd)
+static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
{
pud_t *l3;
pmd_t *l2;
@@ -1415,6 +1470,9 @@
l2 = m2v(l3[pud_index(__START_KERNEL_map + PMD_SIZE)].pud);
memcpy(level2_fixmap_pgt, l2, sizeof(pmd_t) * PTRS_PER_PMD);

+ /* Set up identity map */
+ xen_map_identity_early(max_pfn);
+
/* Make pagetable pieces RO */
set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
@@ -1424,7 +1482,7 @@
set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);

/* Pin down new L4 */
- pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE, PFN_DOWN(__pa(init_level4_pgt)));
+ pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE, PFN_DOWN(__pa_symbol(init_level4_pgt)));

/* Unpin Xen-provided one */
pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
@@ -1433,18 +1491,22 @@
pgd = init_level4_pgt;
xen_write_cr3(__pa(pgd));

- max_pfn_mapped = PFN_DOWN(__pa(pgd) +
- xen_start_info->nr_pt_frames*PAGE_SIZE +
- 512*1024);
+ reserve_early(__pa(xen_start_info->pt_base),
+ __pa(xen_start_info->pt_base +
+ xen_start_info->nr_pt_frames * PAGE_SIZE),
+ "XEN PAGETABLES");

return pgd;
}
#else
-static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd)
+static __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
{
init_pg_tables_start = __pa(pgd);
init_pg_tables_end = __pa(pgd) + xen_start_info->nr_pt_frames*PAGE_SIZE;
max_pfn_mapped = PFN_DOWN(init_pg_tables_end + 512*1024);
+
+ x86_write_percpu(xen_cr3, __pa(pgd));
+ x86_write_percpu(xen_current_cr3, __pa(pgd));

return pgd;
}
@@ -1502,14 +1564,11 @@
per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];

xen_raw_console_write("mapping kernel into physical memory\n");
- pgd = xen_setup_kernel_pagetable(pgd);
+ pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);

init_mm.pgd = pgd;

/* keep using Xen gdt for now; no urgent need to change it */
-
- x86_write_percpu(xen_cr3, __pa(pgd));
- x86_write_percpu(xen_current_cr3, __pa(pgd));

pv_info.kernel_rpl = 1;
if (xen_feature(XENFEAT_supervisor_mode_kernel))



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