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authorPaolo Bonzini <pbonzini@redhat.com>2015-08-07 12:27:54 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-08-07 12:46:32 +0200
commit18c3626e3d5dfa8b90e2dc6dbc30064c0e1c97ad (patch)
tree023ac1fe38a06a4a4f5845cf87bbe4bc98b4e3ac /arch
parentfc1a8126bf8095b10f5a79893f2d2b19227f88f2 (diff)
KVM: x86: zero IDT limit on entry to SMM
The recent BlackHat 2015 presentation "The Memory Sinkhole" mentions that the IDT limit is zeroed on entry to SMM. This is not documented, and must have changed some time after 2010 (see http://www.ssi.gouv.fr/uploads/IMG/pdf/IT_Defense_2010_final.pdf). KVM was not doing it, but the fix is easy. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5ef2560075bf..c5e88a881899 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6327,6 +6327,7 @@ static void process_smi_save_state_64(struct kvm_vcpu *vcpu, char *buf)
static void process_smi(struct kvm_vcpu *vcpu)
{
struct kvm_segment cs, ds;
+ struct desc_ptr dt;
char buf[512];
u32 cr0;
@@ -6359,6 +6360,10 @@ static void process_smi(struct kvm_vcpu *vcpu)
kvm_x86_ops->set_cr4(vcpu, 0);
+ /* Undocumented: IDT limit is set to zero on entry to SMM. */
+ dt.address = dt.size = 0;
+ kvm_x86_ops->set_idt(vcpu, &dt);
+
__kvm_set_dr(vcpu, 7, DR7_FIXED_1);
cs.selector = (vcpu->arch.smbase >> 4) & 0xffff;