x86/espfix/xen: Fix allocation of pages for paravirt page tables
authorBoris Ostrovsky <boris.ostrovsky@oracle.com>
Wed, 9 Jul 2014 17:18:18 +0000 (13:18 -0400)
committerBen Hutchings <ben@decadent.org.uk>
Sat, 13 Sep 2014 22:41:51 +0000 (23:41 +0100)
commit060e7f67c88ebbcf8745505c7ccf44c53601f7de
treeb56aaf65f3601caa18a51b45a3a1a76ddbe9b84e
parent8ba19cd8c351e16b6be4caca9338d19b0cb8eaa4
x86/espfix/xen: Fix allocation of pages for paravirt page tables

commit 8762e5092828c4dc0f49da5a47a644c670df77f3 upstream.

init_espfix_ap() is currently off by one level when informing hypervisor
that allocated pages will be used for ministacks' page tables.

The most immediate effect of this on a PV guest is that if
'stack_page = __get_free_page()' returns a non-zeroed-out page the hypervisor
will refuse to use it for a page table (which it shouldn't be anyway). This will
result in warnings by both Xen and Linux.

More importantly, a subsequent write to that page (again, by a PV guest) is
likely to result in fatal page fault.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: http://lkml.kernel.org/r/1404926298-5565-1-git-send-email-boris.ostrovsky@oracle.com
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
arch/x86/kernel/espfix_64.c