> On 9 Dec 2019, at 17:28, Nadav Amit <nadav.amit@xxxxxxxxx> wrote:
>
>> On Dec 5, 2019, at 1:54 PM, Liran Alon <liran.alon@xxxxxxxxxx> wrote:
>>
>>
>>
>>> On 5 Dec 2019, at 23:30, Jim Mattson <jmattson@xxxxxxxxxx> wrote:
>>>
>>> On Thu, Dec 5, 2019 at 5:11 AM Jim Mattson <jmattson@xxxxxxxxxx> wrote:
>>>> On Thu, Dec 5, 2019 at 3:46 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>>>>> On 04/12/19 22:40, Jim Mattson wrote:
>>>>>> According to the SDM, a VMWRITE in VMX non-root operation with an
>>>>>> invalid VMCS-link pointer results in VMfailInvalid before the validity
>>>>>> of the VMCS field in the secondary source operand is checked.
>>>>>>
>>>>>> Fixes: 6d894f498f5d1 ("KVM: nVMX: vmread/vmwrite: Use shadow vmcs12 if running L2")
>>>>>> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
>>>>>> Cc: Liran Alon <liran.alon@xxxxxxxxxx>
>>>>>> ---
>>>>>> arch/x86/kvm/vmx/nested.c | 38 +++++++++++++++++++-------------------
>>>>>> 1 file changed, 19 insertions(+), 19 deletions(-)
>>>>>
>>>>> As Vitaly pointed out, the test must be split in two, like this:
>>>>
>>>> Right. Odd that no kvm-unit-tests noticed.
>>>>
>>>>> ---------------- 8< -----------------------
>>>>> From 3b9d87060e800ffae2bd19da94ede05018066c87 Mon Sep 17 00:00:00 2001
>>>>> From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>>>>> Date: Thu, 5 Dec 2019 12:39:07 +0100
>>>>> Subject: [PATCH] kvm: nVMX: VMWRITE checks VMCS-link pointer before VMCS field
>>>>>
>>>>> According to the SDM, a VMWRITE in VMX non-root operation with an
>>>>> invalid VMCS-link pointer results in VMfailInvalid before the validity
>>>>> of the VMCS field in the secondary source operand is checked.
>>>>>
>>>>> While cleaning up handle_vmwrite, make the code of handle_vmread look
>>>>> the same, too.
>>>>
>>>> Okay.
>>>>
>>>>> Fixes: 6d894f498f5d1 ("KVM: nVMX: vmread/vmwrite: Use shadow vmcs12 if running L2")
>>>>> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
>>>>> Cc: Liran Alon <liran.alon@xxxxxxxxxx>
>>>>>
>>>>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>>>>> index 4aea7d304beb..c080a879b95d 100644
>>>>> --- a/arch/x86/kvm/vmx/nested.c
>>>>> +++ b/arch/x86/kvm/vmx/nested.c
>>>>> @@ -4767,14 +4767,13 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
>>>>> if (to_vmx(vcpu)->nested.current_vmptr == -1ull)
>>>>> return nested_vmx_failInvalid(vcpu);
>>>>>
>>>>> - if (!is_guest_mode(vcpu))
>>>>> - vmcs12 = get_vmcs12(vcpu);
>>>>> - else {
>>>>> + vmcs12 = get_vmcs12(vcpu);
>>>>> + if (is_guest_mode(vcpu)) {
>>>>> /*
>>>>> * When vmcs->vmcs_link_pointer is -1ull, any VMREAD
>>>>> * to shadowed-field sets the ALU flags for VMfailInvalid.
>>>>> */
>>>>> - if (get_vmcs12(vcpu)->vmcs_link_pointer == -1ull)
>>>>> + if (vmcs12->vmcs_link_pointer == -1ull)
>>>>> return nested_vmx_failInvalid(vcpu);
>>>>> vmcs12 = get_shadow_vmcs12(vcpu);
>>>>> }
>>>>> @@ -4878,8 +4877,19 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
>>>>> }
>>>>> }
>>>>>
>>>>> + vmcs12 = get_vmcs12(vcpu);
>>>>> + if (is_guest_mode(vcpu)) {
>>>>> + /*
>>>>> + * When vmcs->vmcs_link_pointer is -1ull, any VMWRITE
>>>>> + * to shadowed-field sets the ALU flags for VMfailInvalid.
>>>>> + */
>>>>> + if (vmcs12->vmcs_link_pointer == -1ull)
>>>>> + return nested_vmx_failInvalid(vcpu);
>>>>> + vmcs12 = get_shadow_vmcs12(vcpu);
>>>>> + }
>>>>>
>>>>> field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
>>>>> +
>>>>> /*
>>>>> * If the vCPU supports "VMWRITE to any supported field in the
>>>>> * VMCS," then the "read-only" fields are actually read/write.
>>>>> @@ -4889,24 +4899,12 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
>>>>> return nested_vmx_failValid(vcpu,
>>>>> VMXERR_VMWRITE_READ_ONLY_VMCS_COMPONENT);
>>>>>
>>>>> - if (!is_guest_mode(vcpu)) {
>>>>> - vmcs12 = get_vmcs12(vcpu);
>>>>> -
>>>>> - /*
>>>>> - * Ensure vmcs12 is up-to-date before any VMWRITE that dirties
>>>>> - * vmcs12, else we may crush a field or consume a stale value.
>>>>> - */
>>>>> - if (!is_shadow_field_rw(field))
>>>>> - copy_vmcs02_to_vmcs12_rare(vcpu, vmcs12);
>>>>> - } else {
>>>>> - /*
>>>>> - * When vmcs->vmcs_link_pointer is -1ull, any VMWRITE
>>>>> - * to shadowed-field sets the ALU flags for VMfailInvalid.
>>>>> - */
>>>>> - if (get_vmcs12(vcpu)->vmcs_link_pointer == -1ull)
>>>>> - return nested_vmx_failInvalid(vcpu);
>>>>> - vmcs12 = get_shadow_vmcs12(vcpu);
>>>>> - }
>>>>> + /*
>>>>> + * Ensure vmcs12 is up-to-date before any VMWRITE that dirties
>>>>> + * vmcs12, else we may crush a field or consume a stale value.
>>>>> + */
>>>>> + if (!is_guest_mode(vcpu) && !is_shadow_field_rw(field))
>>>>> + copy_vmcs02_to_vmcs12_rare(vcpu, vmcs12);
>>>>>
>>>>> offset = vmcs_field_to_offset(field);
>>>>> if (offset < 0)
>>>>>
>>>>>
>>>>> ... and also, do you have a matching kvm-unit-tests patch?
>>>>
>>>> I'll put one together, along with a test that shows the current
>>>> priority inversion between read-only and unsupported VMCS fields.
>>>
>>> I can't figure out how to clear IA32_VMX_MISC[bit 29] in qemu, so I'm
>>> going to add the test to tools/testing/selftests/kvm instead.
>>
>> Please don’t.
>>
>> I wish that we keep clear separation between kvm-unit-tests and self-tests.
>> In the sense that kvm-unit-tests tests for correct CPU behaviour semantics
>> and self-tests tests for correctness of KVM userspace API.
>>
>> In the future, I wish to change kvm-unit-tests to cpu-unit-tests. As there is no
>> real connection to KVM. It’s a bunch of tests that can be run on top of any CPU
>> Implementation (weather vCPU by some hypervisor or bare-metal CPU) and
>> test for it’s semantics.
>> I have already used this to find semantic issues on Hyper-V vCPU implementation for example.
>
> Did you use for the matter the “infrastructure” that I added?
>
No. It’s possible to just change QEMU to run with WHPX.
But it’s true that the “infra” you added for running on Bare-Metal should work as-well.
This is why I wish to change kvm-unit-tests to cpu-unit-tests. :)
-Liran
