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>

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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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2

arch/x86/xen/enlighten_pv.c

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2

arch/x86/xen/mmu_pv.c

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