linux-kernel - Re: [PATCH 3/4] KVM/VMX: Add identical ept table pointer check

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Message-ID: <0551a777-880a-5019-6e9e-6c0fb5816525@microsoft.com>
Date:   Wed, 4 Jul 2018 06:24:57 +0000
From:   Tianyu Lan <Tianyu.Lan@...rosoft.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: Re: [PATCH 3/4] KVM/VMX: Add identical ept table pointer check

Hi Sean:
	Thank for your review.


On 7/3/2018 1:29 AM, Sean Christopherson wrote:
> On Mon, Jul 02, 2018 at 02:17:29PM +0000, Tianyu Lan wrote:
>> This patch is to check ept table pointer of each cpus when set ept
>> tables and store identical ept table pointer if all ept table pointers
>> of single VM are same. This is for support of para-virt ept flush
>> hypercall.
>>
>> Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
>> ---
>>   arch/x86/kvm/vmx.c | 31 +++++++++++++++++++++++++++++++
>>   1 file changed, 31 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 1689f433f3a0..0b1e4e9fef2b 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -194,6 +194,9 @@ struct kvm_vmx {
>>   	unsigned int tss_addr;
>>   	bool ept_identity_pagetable_done;
>>   	gpa_t ept_identity_map_addr;
>> +
>> +	u64 identical_ept_pointer;
>> +	spinlock_t ept_pointer_lock;
>>   };
>>   
>>   #define NR_AUTOLOAD_MSRS 8
>> @@ -853,6 +856,7 @@ struct vcpu_vmx {
>>   	 */
>>   	u64 msr_ia32_feature_control;
>>   	u64 msr_ia32_feature_control_valid_bits;
>> +	u64 ept_pointer;
>>   };
>>   
>>   enum segment_cache_field {
>> @@ -4958,6 +4962,29 @@ static u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
>>   	return eptp;
>>   }
>>   
>> +static void check_ept_pointer(struct kvm_vcpu *vcpu, u64 eptp)
>> +{
>> +	struct kvm *kvm = vcpu->kvm;
>> +	u64 tmp_eptp = INVALID_PAGE;
>> +	int i;
>> +
>> +	spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
>> +	to_vmx(vcpu)->ept_pointer = eptp;
>> +
>> +	kvm_for_each_vcpu(i, vcpu, kvm) {
>> +		if (!VALID_PAGE(tmp_eptp)) {
>> +			tmp_eptp = to_vmx(vcpu)->ept_pointer;
>> +		} else if (tmp_eptp != to_vmx(vcpu)->ept_pointer) {
>> +			to_kvm_vmx(kvm)->identical_ept_pointer = INVALID_PAGE;
>> +			spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
>> +			return;
>> +		}
>> +	}
>> +
>> +	to_kvm_vmx(kvm)->identical_ept_pointer = tmp_eptp;
>> +	spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
>> +}
>> +
>>   static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>>   {
>>   	unsigned long guest_cr3;
>> @@ -4967,6 +4994,8 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
>>   	if (enable_ept) {
>>   		eptp = construct_eptp(vcpu, cr3);
>>   		vmcs_write64(EPT_POINTER, eptp);
>> +		check_ept_pointer(vcpu, eptp);
> 
> Shouldn't this call, or the function itself, be conditional on Hyper-V
> or remote flushing, e.g. by checking kvm_x86_ops->tlb_remote_flush?
> 

Yes, good suggestion and will update in the next version.

>> +
>>   		if (enable_unrestricted_guest || is_paging(vcpu) ||
>>   		    is_guest_mode(vcpu))
>>   			guest_cr3 = kvm_read_cr3(vcpu);
>> @@ -10383,6 +10412,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>>   
>>   static int vmx_vm_init(struct kvm *kvm)
>>   {
>> +	spin_lock_init(&to_kvm_vmx(kvm)->ept_pointer_lock);
>> +
>>   	if (!ple_gap)
>>   		kvm->arch.pause_in_guest = true;
>>   	return 0;
>> -- 
>> 2.14.3