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| author | Dongxiao Xu <dongxiao.xu@intel.com> | 2013-04-09 16:26:29 +0200 |
|---|---|---|
| committer | Jan Beulich <jbeulich@suse.com> | 2013-04-09 16:26:29 +0200 |
| commit | a625c40e553907d581aa9fbbab762b64841e2741 (patch) | |
| tree | c0d9b8f3685a5ce6ad291c90400c4bddc826bdc3 | |
| parent | da7e3cdf0a1c2440886383e0e7f826c88796b8ca (diff) | |
| download | xen-a625c40e553907d581aa9fbbab762b64841e2741.tar.gz xen-a625c40e553907d581aa9fbbab762b64841e2741.tar.bz2 xen-a625c40e553907d581aa9fbbab762b64841e2741.zip | |
VMX: disable SMEP feature when guest is in non-paging mode
SMEP is disabled if CPU is in non-paging mode in hardware.
However Xen always uses paging mode to emulate guest non-paging
mode with HAP. 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 in grub. This is because Xen 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>
master commit: e7dda8ec9fc9020e4f53345cdbb18a2e82e54a65
master date: 2013-01-30 09:17:30 -0800
| -rw-r--r-- | xen/arch/x86/hvm/vmx/vmx.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c index 88eeb9d352..e720c148b2 100644 --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -1186,6 +1186,13 @@ static void vmx_update_guest_cr(struct vcpu *v, unsigned int cr) { v->arch.hvm_vcpu.hw_cr[4] |= X86_CR4_PSE; v->arch.hvm_vcpu.hw_cr[4] &= ~X86_CR4_PAE; + /* + * SMEP is disabled if CPU is in non-paging mode in hardware. + * However Xen always uses paging mode to emulate guest non-paging + * mode with HAP. To emulate this behavior, SMEP needs to be + * manually disabled when guest switches to non-paging mode. + */ + v->arch.hvm_vcpu.hw_cr[4] &= ~X86_CR4_SMEP; } __vmwrite(GUEST_CR4, v->arch.hvm_vcpu.hw_cr[4]); __vmwrite(CR4_READ_SHADOW, v->arch.hvm_vcpu.guest_cr[4]); |