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

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Message-ID: <3460bd57-6fdd-f73c-9ce0-c97d4cc85f63@oracle.com>
Date:   Wed, 25 Sep 2019 16:55:15 -0700
From:   Krish Sadhukhan <krish.sadhukhan@...cle.com>
To:     Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH] KVM: nVMX: cleanup and fix host 64-bit mode checks



On 09/25/2019 09:47 AM, Jim Mattson wrote:
> On Wed, Sep 25, 2019 at 9:34 AM Paolo Bonzini <pbonzini@...hat.com> 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@...el.com>
>> Cc: Jim Mattson <jmattson@...gle.com>
>> Cc: Krish Sadhukhan <krish.sadhukhan@...cle.com>
>> Fixes: 5845038c111db27902bc220a4f70070fe945871c
>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>> ---
>>   arch/x86/kvm/vmx/nested.c | 53 ++++++++++++++++++++---------------------------
>>   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,
>>              CC(!kvm_pat_valid(vmcs12->host_ia32_pat)))
>>                  return -EINVAL;
>>
>> -       ia32e = (vmcs12->vm_exit_controls &
>> -                VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
>> +#ifdef CONFIG_X86_64
>> +       ia32e = !!(vcpu->arch.efer & EFER_LMA);
>> +#else
>> +       if (CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE))
>> +               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 ?

>
>> +
>> +       ia32e = false;
>> +#endif
>> +
>> +       if (ia32e) {
>> +               if (CC(!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) ||
>> +                   CC(!(vmcs12->host_cr4 & X86_CR4_PAE)))
>> +                       return -EINVAL;
>> +       } else {
>> +               if (CC(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) ||
>> +                   CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
>> +                   CC(vmcs12->host_cr4 & X86_CR4_PCIDE) ||
>> +                   CC(((vmcs12->host_rip) >> 32) & 0xffffffff))
> The mask shouldn't be necessary.
>
>> +                       return -EINVAL;
>> +       }
>>
>>          if (CC(vmcs12->host_cs_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK)) ||
>>              CC(vmcs12->host_ss_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK)) ||
>> @@ -2684,35 +2702,8 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
>>              CC(is_noncanonical_address(vmcs12->host_gs_base, vcpu)) ||
>>              CC(is_noncanonical_address(vmcs12->host_gdtr_base, vcpu)) ||
>>              CC(is_noncanonical_address(vmcs12->host_idtr_base, vcpu)) ||
>> -           CC(is_noncanonical_address(vmcs12->host_tr_base, vcpu)))
>> -               return -EINVAL;
>> -
>> -       if (!(vmcs12->host_ia32_efer & EFER_LMA) &&
>> -           ((vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
>> -           (vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE))) {
>> -               return -EINVAL;
>> -       }
>> -
>> -       if ((vmcs12->host_ia32_efer & EFER_LMA) &&
>> -           !(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) {
>> -               return -EINVAL;
>> -       }
>> -
>> -       if (!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) &&
>> -           ((vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
>> -           (vmcs12->host_cr4 & X86_CR4_PCIDE) ||
>> -           (((vmcs12->host_rip) >> 32) & 0xffffffff))) {
>> -               return -EINVAL;
>> -       }
>> -
>> -       if ((vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) &&
>> -           ((!(vmcs12->host_cr4 & X86_CR4_PAE)) ||
>> -           (is_noncanonical_address(vmcs12->host_rip, vcpu)))) {
>> -               return -EINVAL;
>> -       }
>> -#else
>> -       if (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE ||
>> -           vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)
>> +           CC(is_noncanonical_address(vmcs12->host_tr_base, vcpu)) ||
>> +           CC(is_noncanonical_address(vmcs12->host_rip, vcpu)))
>>                  return -EINVAL;
>>   #endif
>>
>> --
>> 1.8.3.1
>>
> Reviewed-by: Jim Mattson <jmattson@...gle.com>