Commit 75f2d3a0 authored by Juergen Gross's avatar Juergen Gross Committed by Boris Ostrovsky
Browse files

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



Commit 7b25b9cb ("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: 7b25b9cb ("x86/xen/time: Initialize pv xen time in init_hypervisor_platform()")
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
parent 00f53f75

arch/x86/mm/init.c

+12 −5
Original line number Diff line number Diff line
@@ -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;

arch/x86/xen/enlighten_pv.c

+2 −0
Original line number Diff line number Diff line
@@ -122,6 +122,8 @@ static void __init xen_banner(void) 


static void __init xen_pv_init_platform(void)

{

	populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));



	set_fixmap(FIX_PARAVIRT_BOOTMAP, xen_start_info->shared_info);

	HYPERVISOR_shared_info = (void *)fix_to_virt(FIX_PARAVIRT_BOOTMAP);

arch/x86/xen/mmu_pv.c

+2 −0
Original line number Diff line number Diff line
@@ -2171,6 +2171,8 @@ void __init xen_relocate_p2m(void) 
#else	/* !CONFIG_X86_64 */

static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);

static RESERVE_BRK_ARRAY(pmd_t, swapper_kernel_pmd, PTRS_PER_PMD);

RESERVE_BRK(fixup_kernel_pmd, PAGE_SIZE);

RESERVE_BRK(fixup_kernel_pte, PAGE_SIZE);



static void __init xen_write_cr3_init(unsigned long cr3)

{

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