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x86/xen: enable early use of set_fixmap in 32-bit Xen PV guest

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Commit 7b25b9cb0d ("x86/xen/time: Initialize pv xen time in
init_hypervisor_platform()") moved the mapping of the shared info area
before pagetable_init(). This breaks booting as 32-bit PV guest as the
use of set_fixmap isn't possible at this time on 32-bit.

This can be worked around by populating the needed PMD on 32-bit
kernel earlier.

In order not to reimplement populate_extra_pte() using extend_brk()
for allocating new page tables extend alloc_low_pages() to do that in
case the early page table pool is not yet available.

Fixes: 7b25b9cb0d ("x86/xen/time: Initialize pv xen time in init_hypervisor_platform()")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
Juergen Gross
2018-08-20 17:24:20 +02:00
committed by Boris Ostrovsky
parent 00f53f758d
commit 75f2d3a0ce
3 changed files with 16 additions and 5 deletions
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17
arch/x86/mm/init.c
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@@ -99,15 +99,22 @@ __ref void *alloc_low_pages(unsigned int num)
}
if ((pgt_buf_end + num) > pgt_buf_top || !can_use_brk_pgt) {
unsigned long ret;
if (min_pfn_mapped >= max_pfn_mapped)
panic("alloc_low_pages: ran out of memory");
ret = memblock_find_in_range(min_pfn_mapped << PAGE_SHIFT,
unsigned long ret = 0;
if (min_pfn_mapped < max_pfn_mapped) {
ret = memblock_find_in_range(
min_pfn_mapped << PAGE_SHIFT,
max_pfn_mapped << PAGE_SHIFT,
PAGE_SIZE * num , PAGE_SIZE);
}
if (ret)
memblock_reserve(ret, PAGE_SIZE * num);
else if (can_use_brk_pgt)
ret = __pa(extend_brk(PAGE_SIZE * num, PAGE_SIZE));
if (!ret)
panic("alloc_low_pages: can not alloc memory");
memblock_reserve(ret, PAGE_SIZE * num);
pfn = ret >> PAGE_SHIFT;
} else {
pfn = pgt_buf_end;