Re: [v2 1/1] xen, mm: Allow deferred page initialization for xen pv domains

* Pavel Tatashin [off-list ref] wrote:

Juergen Gross noticed that commit
f7f99100d8d ("mm: stop zeroing memory during allocation in vmemmap")
broke XEN PV domains when deferred struct page initialization is enabled.

This is because the xen's PagePinned() flag is getting erased from struct
pages when they are initialized later in boot.

Juergen fixed this problem by disabling deferred pages on xen pv domains.
It is desirable, however, to have this feature available as it reduces boot
time. This fix re-enables the feature for pv-dmains, and fixes the problem
the following way:

The fix is to delay setting PagePinned flag until struct pages for all
allocated memory are initialized, i.e. until after free_all_bootmem().

A new x86_init.hyper op init_after_bootmem() is called to let xen know
that boot allocator is done, and hence struct pages for all the allocated
memory are now initialized. If deferred page initialization is enabled, the
rest of struct pages are going to be initialized later in boot once
page_alloc_init_late() is called.

xen_after_bootmem() walks page table's pages and marks them pinned.

Signed-off-by: Pavel Tatashin <redacted>
---
 arch/x86/include/asm/x86_init.h |  2 ++
 arch/x86/kernel/x86_init.c      |  1 +
 arch/x86/mm/init_32.c           |  1 +
 arch/x86/mm/init_64.c           |  1 +
 arch/x86/xen/mmu_pv.c           | 38 ++++++++++++++++++++++++++------------
 mm/page_alloc.c                 |  4 ----
 6 files changed, 31 insertions(+), 16 deletions(-)

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo