Re: [PATCH] KVM: nVMX: cleanup and fix host 64-bit mode checks

[Paolo Bonzini]

On 26/09/19 01:55, Krish Sadhukhan wrote:
> 
> 
> On 09/25/2019 09:47 AM, Jim Mattson wrote:
>> On Wed, Sep 25, 2019 at 9:34 AM Paolo Bonzini <pbonzini@xxxxxxxxxx>
>> wrote:
>>> KVM was incorrectly checking vmcs12->host_ia32_efer even if the "load
>>> IA32_EFER" exit control was reset. Also, some checks were not using
>>> the new CC macro for tracing.
>>>
>>> Cleanup everything so that the vCPU's 64-bit mode is determined
>>> directly from EFER_LMA and the VMCS checks are based on that, which
>>> matches section 26.2.4 of the SDM.
>>>
>>> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>>> Cc: Jim Mattson <jmattson@xxxxxxxxxx>
>>> Cc: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
>>> Fixes: 5845038c111db27902bc220a4f70070fe945871c
>>> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>>> ---
>>> Â arch/x86/kvm/vmx/nested.c | 53
>>> ++++++++++++++++++++---------------------------
>>> Â 1 file changed, 22 insertions(+), 31 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>>> index 70d59d9304f2..e108847f6cf8 100644
>>> --- a/arch/x86/kvm/vmx/nested.c
>>> +++ b/arch/x86/kvm/vmx/nested.c
>>> @@ -2664,8 +2664,26 @@ static int nested_vmx_check_host_state(struct
>>> kvm_vcpu *vcpu,
>>> ÂÂÂÂÂÂÂÂÂÂÂÂ CC(!kvm_pat_valid(vmcs12->host_ia32_pat)))
>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return -EINVAL;
>>>
>>> -ÂÂÂÂÂÂ ia32e = (vmcs12->vm_exit_controls &
>>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
>>> +#ifdef CONFIG_X86_64
>>> +ÂÂÂÂÂÂ ia32e = !!(vcpu->arch.efer & EFER_LMA);
>>> +#else
>>> +ÂÂÂÂÂÂ if (CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE))
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return -EINVAL;
>> This check is redundant, since it is checked in the else block below.
> 
> Should we be re-using is_long_mode() instead of duplicating the code ?

Of course!  I have already pushed the patch, but I will send a follow up.

Paolo