On 06/11/17 11:27, Paolo Bonzini wrote:
On 05/11/2017 17:15, Liran Alon wrote:
When running L2, #UD should be intercepted by L1 or just forwarded
directly to L2. It should not reach L0 x86 emulator.
Therefore, set intercept for #UD only based on L1 exception-bitmap.
Also add BUG_ON() on L0 #UD intercept handlers to make sure it is never
reached while running L2.
This improves commit ae1f57670703 ("KVM: nVMX: Do not emulate #UD while
in guest mode") by removing an unnecessary exit from L2 to L0 on #UD
when L1 doesn't intercept it.
In addition, SVM L0 #UD intercept handler doesn't handle correctly the
case it is raised from L2. In this case, it should forward the #UD to
guest instead of x86 emulator. As done in VMX #UD intercept handler.
This commit fixes this issue as-well.
Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
arch/x86/kvm/svm.c | 4 +++-
arch/x86/kvm/vmx.c | 9 ++++-----
2 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0e68f0b3cbf7..1c7f76a417e7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1221,7 +1221,8 @@ static void init_vmcb(struct vcpu_svm *svm)
set_dr_intercepts(svm);
set_exception_intercept(svm, PF_VECTOR);
- set_exception_intercept(svm, UD_VECTOR);
+ if (!is_guest_mode(&svm->vcpu))
+ set_exception_intercept(svm, UD_VECTOR);
set_exception_intercept(svm, MC_VECTOR);
set_exception_intercept(svm, AC_VECTOR);
set_exception_intercept(svm, DB_VECTOR);
This is not called on every vmexit. The right place to touch is
recalc_intercepts. Then on vmexit it will be automatically restored
when nested_svm_vmexit calls copy_vmcb_control_area.
Agreed. My bad. Will fix in v2 of this commit.
@@ -2188,6 +2189,7 @@ static int ud_interception(struct vcpu_svm *svm)
{
int er;
+ BUG_ON(is_guest_mode(&svm->vcpu));
er = emulate_instruction(&svm->vcpu, EMULTYPE_TRAP_UD);
if (er != EMULATE_DONE)
kvm_queue_exception(&svm->vcpu, UD_VECTOR);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 95a01609d7ee..5e2c47dd0c83 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1878,7 +1878,7 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu)
{
u32 eb;
- eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) |
+ eb = (1u << PF_VECTOR) | (1u << MC_VECTOR) |
(1u << DB_VECTOR) | (1u << AC_VECTOR);
if ((vcpu->guest_debug &
(KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) ==
@@ -1896,6 +1896,8 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu)
*/
if (is_guest_mode(vcpu))
eb |= get_vmcs12(vcpu)->exception_bitmap;
+ else
+ eb |= 1u << UD_VECTOR;
It's a nit, but since you have to send a v2, I'd prefer to keep
UD_VECTOR above and clear it here.
I think your suggestion could be problematic.
In case (to_vmx(vcpu)->rmode.vm86_active == true) then we would like to
intercept all exceptions and therefore not clear UD_VECTOR.
This is why I preferred this approach.
Thanks,
Paolo
vmcs_write32(EXCEPTION_BITMAP, eb);
}
@@ -5881,10 +5883,7 @@ static int handle_exception(struct kvm_vcpu *vcpu)
return 1; /* already handled by vmx_vcpu_run() */
if (is_invalid_opcode(intr_info)) {
- if (is_guest_mode(vcpu)) {
- kvm_queue_exception(vcpu, UD_VECTOR);
- return 1;
- }
+ BUG_ON(is_guest_mode(vcpu));
er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
if (er != EMULATE_DONE)
kvm_queue_exception(vcpu, UD_VECTOR);
