2015-02-23 19:05+0100, Kashyap Chamarthy:
> Tested with the _correct_ Kernel[1] (that has Radim's patch) now --
> applied it on both L0 and L1.
>
> Result: Same as before -- Booting L2 causes L1 to reboot. However, the
> stack trace from `dmesg` on L0 is took slightly different path than
> before -- it's using MSR handling:
Thanks, the problem was deeper ... L1 enabled unrestricted mode while L0
had it disabled. L1 could then vmrun a L2 state that L0 would have to
emulate, but that doesn't work. There are at least these solutions:
1) don't expose unrestricted_guest when L0 doesn't have it
2) fix unrestricted mode emulation code
3) handle the failure a without killing L1
I'd do just (1) -- emulating unrestricted mode is a loss.
I have done initial testing and at least qemu-sanity-check works now:
---8<---
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")
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f7b20b417a3a..dbabea21357b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2476,8 +2476,7 @@ 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;
@@ -2491,6 +2490,10 @@ 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,
--
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