From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: kvm@vger.kernel.org, rkrcmar@redhat.com, pbonzini@redhat.com,
jmattson@google.com
Subject: Re: [PATCH 3/4] kvm-unit-test: nVMX: __enter_guest() should not set "launched" state when VM-entry fails
Date: Fri, 13 Sep 2019 14:06:45 -0700 [thread overview]
Message-ID: <20190913210645.GA14482@linux.intel.com> (raw)
In-Reply-To: <a2268863-e554-4547-5196-3509bda3ace3@oracle.com>
On Fri, Sep 13, 2019 at 01:37:55PM -0700, Krish Sadhukhan wrote:
>
> On 9/4/19 8:42 AM, Sean Christopherson wrote:
> >On Thu, Aug 29, 2019 at 04:56:34PM -0400, Krish Sadhukhan wrote:
> >>Bit# 31 in VM-exit reason is set by hardware in both cases of early VM-entry
> >>failures and VM-entry failures due to invalid guest state.
> >This is incorrect, VMCS.EXIT_REASON is not written on a VM-Fail. If the
> >tests are passing, you're probably consuming a stale EXIT_REASON.
>
> In vmx_vcpu_run(),
>
> if (vmx->fail || (vmx->exit_reason &
> VMX_EXIT_REASONS_FAILED_VMENTRY))
> return;
>
> vmx->loaded_vmcs->launched = 1;
>
> we return without setting "launched" whenever bit# 31 is set in Exit Reason.
> If VM-entry fails due to invalid guest state or due to errors in VM-entry
> MSR-loading area, bit#31 is set. As a result, L2 is not in "launched" state
> when we return to L1. Tests that want to VMRESUME L2 after fixing the bad
> guest state or the bad MSR-loading area, fail with VM-Instruction Error 5,
>
> "Early vmresume failure: error number is 5. See Intel 30.4."
Yes, a VMCS isn't marked launched if it generates a VM-Exit due to a
failed consistency check. But as that code shows, a failed consistency
check results in said VM-Exit *or* a VM-Fail. Cosnsitency checks that
fail early, i.e. before loading guest state, generate VM-Fail, any check
that fails after the CPU has started loading guest state manifests as a
VM-Exit. VMCS.EXIT_REASON isn't touched in the VM-Fail case.
E.g. in CHECKS ON VMX CONTROLS AND HOST-STATE AREA, the SDM states:
VM entry fails if any of these checks fail. When such failures occur,
control is passed to the next instruction, RFLAGS.ZF is set to 1 to
indicate the failure, and the VM-instruction error field is loaded with
an error number that indicates whether the failure was due to the
controls or the host-state area (see Chapter 30).
next prev parent reply other threads:[~2019-09-13 21:06 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 20:56 [PATCH 0/4] KVM: nVMX: Check GUEST_DEBUGCTL and GUEST_DR7 on vmentry of nested guests Krish Sadhukhan
2019-08-29 20:56 ` [PATCH 1/4] KVM: nVMX: Check GUEST_DEBUGCTL " Krish Sadhukhan
2019-08-29 22:12 ` Jim Mattson
2019-08-30 23:26 ` Krish Sadhukhan
2019-09-01 23:55 ` Jim Mattson
2019-08-29 20:56 ` [PATCH 2/4] KVM: nVMX: Check GUEST_DR7 " Krish Sadhukhan
2019-08-29 22:26 ` Jim Mattson
2019-08-30 23:07 ` Krish Sadhukhan
2019-08-30 23:15 ` Jim Mattson
2019-09-02 0:33 ` Jim Mattson
[not found] ` <e229bea2-acb2-e268-6281-d8e467c3282e@oracle.com>
2019-09-04 16:44 ` Jim Mattson
2019-09-04 16:58 ` Sean Christopherson
2019-09-04 18:05 ` Krish Sadhukhan
2019-09-04 18:20 ` Jim Mattson
2019-09-09 4:11 ` Krish Sadhukhan
2019-09-09 15:56 ` Jim Mattson
2019-09-04 17:14 ` Sean Christopherson
2019-12-20 23:45 ` Jim Mattson
2019-12-21 0:27 ` Jim Mattson
2019-08-29 20:56 ` [PATCH 3/4] kvm-unit-test: nVMX: __enter_guest() should not set "launched" state when VM-entry fails Krish Sadhukhan
2019-09-04 15:42 ` Sean Christopherson
2019-09-13 20:37 ` Krish Sadhukhan
2019-09-13 21:06 ` Sean Christopherson [this message]
2019-09-16 19:12 ` Krish Sadhukhan
2019-08-29 20:56 ` [PATCH 4/4] kvm-unit-test: nVMX: Check GUEST_DEBUGCTL and GUEST_DR7 on vmentry of nested guests Krish Sadhukhan
2019-08-29 23:17 ` Jim Mattson
2019-08-30 1:12 ` Nadav Amit
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