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| author | Dongxiao Xu <dongxiao.xu@intel.com> | 2013-02-04 04:50:43 +0100 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2013-02-06 02:28:07 +0100 |
| commit | c08800a56cb8622bb61577abb4a120c6fdc4b9be (patch) | |
| tree | c9195953c1e901dfa44238facd4fc1402d1b9fc8 /arch/x86/kvm | |
| parent | KVM: Remove duplicate text in api.txt (diff) | |
| download | linux-c08800a56cb8622bb61577abb4a120c6fdc4b9be.tar.xz linux-c08800a56cb8622bb61577abb4a120c6fdc4b9be.zip | |
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>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/vmx.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 0cf74a641dec..fe9a9cfadbd6 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3227,6 +3227,14 @@ 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; } |