Re: [PATCH 1/2] KVM nVMX: Check Host Segment Registers and Descriptor Tables on vmentry of nested guests

From: Krish Sadhukhan <krish.sadhukhan@oracle.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Cc: rkrcmar@redhat.com, jmattson@google.com
Subject: Re: [PATCH 1/2] KVM nVMX: Check Host Segment Registers and Descriptor Tables on vmentry of nested guests
Date: Wed, 3 Jul 2019 16:57:39 -0700	[thread overview]
Message-ID: <722eb7f6-7617-f45a-4a3a-baa6952f7445@oracle.com> (raw)
In-Reply-To: <00f32b48-28e9-2502-5145-52150f0307ca@redhat.com>

On 07/02/2019 09:25 AM, Paolo Bonzini wrote:
> On 29/06/19 00:14, Krish Sadhukhan wrote:
>> According to section "Checks on Host Segment and Descriptor-Table
>> Registers" in Intel SDM vol 3C, the following checks are performed on
>> vmentry of nested guests:
>>
>>     - In the selector field for each of CS, SS, DS, ES, FS, GS and TR, the
>>       RPL (bits 1:0) and the TI flag (bit 2) must be 0.
>>     - The selector fields for CS and TR cannot be 0000H.
>>     - The selector field for SS cannot be 0000H if the "host address-space
>>       size" VM-exit control is 0.
>>     - On processors that support Intel 64 architecture, the base-address
>>       fields for FS, GS and TR must contain canonical addresses.
>>
>> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
>> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
> All these tests are getting expensive.  Can you look into skipping them
> whenever dirty_vmcs12 is clear?

OK. I am working on it and will send a separate patch-set for that. In 
the meantime, I will send v2 of this patchset containing a fix for a 
compilation error.

Thanks.

> Thanks,
>
> Paolo
>
>> ---
>>   arch/x86/kvm/vmx/nested.c | 26 ++++++++++++++++++++++++--
>>   1 file changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>> index f1a69117ac0f..856a83aa42f5 100644
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -2609,6 +2609,30 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
>>   	    !kvm_pat_valid(vmcs12->host_ia32_pat))
>>   		return -EINVAL;
>>   
>> +	ia32e = (vmcs12->vm_exit_controls &
>> +		 VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
>> +
>> +	if (vmcs12->host_cs_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_ss_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_ds_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_es_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_fs_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_gs_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_tr_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK) ||
>> +	    vmcs12->host_cs_selector == 0 ||
>> +	    vmcs12->host_tr_selector == 0 ||
>> +	    (vmcs12->host_ss_selector == 0 && !ia32e))
>> +		return -EINVAL;
>> +
>> +#ifdef CONFIG_X86_64
>> +	if (is_noncanonical_address(vmcs12->host_fs_base, vcpu) ||
>> +	    is_noncanonical_address(vmcs12->host_gs_base, vcpu) ||
>> +	    is_noncanonical_address(vmcs12->host_gdtr_base, vcpu) ||
>> +	    is_noncanonical_address(vmcs12->host_idtr_base, vcpu) ||
>> +	    is_noncanonical_address(vmcs12->host_tr_base, vcpu))
>> +		return -EINVAL;
>> +#endif
>> +
>>   	/*
>>   	 * If the load IA32_EFER VM-exit control is 1, bits reserved in the
>>   	 * IA32_EFER MSR must be 0 in the field for that register. In addition,
>> @@ -2616,8 +2640,6 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
>>   	 * the host address-space size VM-exit control.
>>   	 */
>>   	if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER) {
>> -		ia32e = (vmcs12->vm_exit_controls &
>> -			 VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
>>   		if (!kvm_valid_efer(vcpu, vmcs12->host_ia32_efer) ||
>>   		    ia32e != !!(vmcs12->host_ia32_efer & EFER_LMA) ||
>>   		    ia32e != !!(vmcs12->host_ia32_efer & EFER_LME))
>>