| Message ID | 1359949843-15570-1-git-send-email-dongxiao.xu@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Feb 04, 2013 at 11:50:43AM +0800, Dongxiao Xu wrote: > Changes from v1 to v2: > - Modify commit message and comments according to Gleb's suggestions. > > 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. > > Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com> > Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com> > --- > arch/x86/kvm/vmx.c | 8 ++++++++ > 1 files changed, 8 insertions(+), 0 deletions(-) Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 9120ae1..70393e2 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3155,6 +3155,14 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) if (!is_paging(vcpu)) { hw_cr4 &= ~X86_CR4_PAE; hw_cr4 |= X86_CR4_PSE; + /* + * 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. + */ + hw_cr4 &= ~X86_CR4_SMEP; } else if (!(cr4 & X86_CR4_PAE)) { hw_cr4 &= ~X86_CR4_PAE; }