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KVM: nVMX: mask unrestricted_guest if disabled on L0

PATCH RESEND Applied Radim Krčmář 3 participants 3 messages Mar 17, 2015 – Mar 18, 2015

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Radim Krčmář

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PATCH RESEND 1/1 KVM: nVMX: mask unrestricted_guest if disabled on L0

If EPT was enabled, unrestricted_guest was allowed in L1 regardless of L0. L1 triple faulted when running L2 guest that required emulation.

Another side effect was 'WARN_ON_ONCE(vmx->nested.nested_run_pending)' in L0's dmesg:

  WARNING: CPU: 0 PID: 0 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0x96e/0xb00 [kvm_intel] ()

Prevent this scenario by masking SECONDARY_EXEC_UNRESTRICTED_GUEST when the host doesn't have it enabled.

Fixes 78051e3b7e35 ("KVM: nVMX: Disable unrestricted mode if ept=0")
Cc [email protected]
Tested-by Kashyap Chamarthy <[email protected]>
Signed-off-by Radim Krčmář <[email protected]>

---
The resend Cc'd stable, as recommended by Bandan, and added Tested-by.

 arch/x86/kvm/vmx.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
arch/x86/kvm/vmx.c +5 -2
index 10a481b7674d..ae4f6d35d19c 100644
@@ -2479,8 +2479,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 	if (enable_ept) {
 		/* nested EPT: emulate EPT also to L1 */
 		vmx->nested.nested_vmx_secondary_ctls_high |=
-			SECONDARY_EXEC_ENABLE_EPT |
-			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+			SECONDARY_EXEC_ENABLE_EPT;
 		vmx->nested.nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT |
 			 VMX_EPTP_WB_BIT | VMX_EPT_2MB_PAGE_BIT |
 			 VMX_EPT_INVEPT_BIT;

@@ -2494,6 +2493,10 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 	} else
 		vmx->nested.nested_vmx_ept_caps = 0;
 
+	if (enable_unrestricted_guest)
+		vmx->nested.nested_vmx_secondary_ctls_high |=
+			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+
 	/* miscellaneous data */
 	rdmsr(MSR_IA32_VMX_MISC,
 		vmx->nested.nested_vmx_misc_low,
Signature · 1 line
2.3.2
#1 lore raw
Quoted 5 lines · Radim Krčmář

If EPT was enabled, unrestricted_guest was allowed in L1 regardless of L0. L1 triple faulted when running L2 guest that required emulation.

Another side effect was 'WARN_ON_ONCE(vmx->nested.nested_run_pending)' in L0's dmesg:

Quoted 8 lines
  WARNING: CPU: 0 PID: 0 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0x96e/0xb00 [kvm_intel] ()

Prevent this scenario by masking SECONDARY_EXEC_UNRESTRICTED_GUEST when the host doesn't have it enabled.

Fixes 78051e3b7e35 ("KVM: nVMX: Disable unrestricted mode if ept=0")
Cc [email protected]
Tested-by Kashyap Chamarthy <[email protected]>

Thanks Radim, for resending it. I was trying to find it in one of the recent pull requests. :-)

Just for forerence, test confirmation:

    http://article.gmane.org/gmane.comp.emulators.kvm.devel/133075

Complete thread related to this topic:

    http://thread.gmane.org/gmane.comp.emulators.kvm.devel/132863
Signature · 1 line
/kashyap
Quoted 35 lines
Signed-off-by Radim Krčmář <[email protected]>

---
The resend Cc'd stable, as recommended by Bandan, and added Tested-by.

 arch/x86/kvm/vmx.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
arch/x86/kvm/vmx.c +5 -2
index 10a481b7674d..ae4f6d35d19c 100644
@@ -2479,8 +2479,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 	if (enable_ept) {
 		/* nested EPT: emulate EPT also to L1 */
 		vmx->nested.nested_vmx_secondary_ctls_high |=
-			SECONDARY_EXEC_ENABLE_EPT |
-			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+			SECONDARY_EXEC_ENABLE_EPT;
 		vmx->nested.nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT |
 			 VMX_EPTP_WB_BIT | VMX_EPT_2MB_PAGE_BIT |
 			 VMX_EPT_INVEPT_BIT;

@@ -2494,6 +2493,10 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 	} else
 		vmx->nested.nested_vmx_ept_caps = 0;
 
+	if (enable_unrestricted_guest)
+		vmx->nested.nested_vmx_secondary_ctls_high |=
+			SECONDARY_EXEC_UNRESTRICTED_GUEST;
+
 	/* miscellaneous data */
 	rdmsr(MSR_IA32_VMX_MISC,
 		vmx->nested.nested_vmx_misc_low,
Signature · 1 line
2.3.2
Applied
#2 lore raw
In reply to Radim Krčmář
Quoted 10 lines · Radim Krčmář

If EPT was enabled, unrestricted_guest was allowed in L1 regardless of L0. L1 triple faulted when running L2 guest that required emulation.

Another side effect was 'WARN_ON_ONCE(vmx->nested.nested_run_pending)' in L0's dmesg:

  WARNING: CPU: 0 PID: 0 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0x96e/0xb00 [kvm_intel] ()

Prevent this scenario by masking SECONDARY_EXEC_UNRESTRICTED_GUEST when the host doesn't have it enabled.

Quoted 6 lines
Fixes 78051e3b7e35 ("KVM: nVMX: Disable unrestricted mode if ept=0")
Cc [email protected]
Tested-by Kashyap Chamarthy <[email protected]>
Signed-off-by Radim Krčmář <[email protected]>

---
The resend Cc'd stable, as recommended by Bandan, and added Tested-by.

Applied to master, thanks.