KVM: VMX: disable SMEP feature when guest is in non-paging mode
authorDongxiao Xu <dongxiao.xu@intel.com>
Mon, 4 Feb 2013 03:50:43 +0000 (11:50 +0800)
committerMarcelo Tosatti <mtosatti@redhat.com>
Wed, 6 Feb 2013 01:28:07 +0000 (23:28 -0200)
commitc08800a56cb8622bb61577abb4a120c6fdc4b9be
treec9195953c1e901dfa44238facd4fc1402d1b9fc8
parent4293b5e5a68074431cafa74d549c1327ba1d0deb
KVM: VMX: disable SMEP feature when guest is in non-paging mode

SMEP is disabled if CPU is in non-paging mode in hardware.
However KVM always uses paging mode to emulate guest non-paging
mode with TDP. To emulate this behavior, SMEP needs to be manually
disabled when guest switches to non-paging mode.

We met an issue that, SMP Linux guest with recent kernel (enable
SMEP support, for example, 3.5.3) would crash with triple fault if
setting unrestricted_guest=0. This is because KVM uses an identity
mapping page table to emulate the non-paging mode, where the page
table is set with USER flag. If SMEP is still enabled in this case,
guest will meet unhandlable page fault and then crash.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
arch/x86/kvm/vmx.c