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[xen master] x86: clear per cpu stub page information in cpu_smpboot_free()
commit 774901788c5614798931a1cb2e20dd8b885f97ab
Author: Juergen Gross <jgross@suse.com>
AuthorDate: Thu Jan 9 11:07:38 2020 +0100
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Thu Jan 9 11:07:38 2020 +0100

x86: clear per cpu stub page information in cpu_smpboot_free()

cpu_smpboot_free() removes the stubs for the cpu going offline, but it
isn't clearing the related percpu variables. This will result in
crashes when a stub page is released due to all related cpus gone
offline and one of those cpus going online later.

Fix that by clearing stubs.addr and stubs.mfn in order to allocate a
new stub page when needed, irrespective of whether the CPU gets parked
or removed.

Fixes: 2e6c8f182c9c50 ("x86: distinguish CPU offlining from CPU removal")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Tao Xu <tao3.xu@intel.com>
---
xen/arch/x86/smpboot.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 7e29704080..301f746979 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -943,6 +943,8 @@ static void cpu_smpboot_free(unsigned int cpu, bool remove)
unmap_domain_page(stub_page);
destroy_xen_mappings(per_cpu(stubs.addr, cpu) & PAGE_MASK,
(per_cpu(stubs.addr, cpu) | ~PAGE_MASK) + 1);
+ per_cpu(stubs.addr, cpu) = 0;
+ per_cpu(stubs.mfn, cpu) = 0;
if ( i == STUBS_PER_PAGE )
free_domheap_page(mfn_to_page(mfn));
}
--
generated by git-patchbot for /home/xen/git/xen.git#master

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