Re: [PATCH v5 4/7] kvm, mem-hotplug: Reload L1' apic access page on migration in vcpu_enter_guest().

[tangchen <tangchen@cn.fujitsu.com>]

On 09/11/2014 05:21 PM, Paolo Bonzini wrote:
> Il 11/09/2014 07:38, Tang Chen ha scritto:
>> apic access page is pinned in memory. As a result, it cannot be migrated/hot-removed.
>> Actually, it is not necessary to be pinned.
>>
>> The hpa of apic access page is stored in VMCS APIC_ACCESS_ADDR pointer. When
>> the page is migrated, kvm_mmu_notifier_invalidate_page() will invalidate the
>> corresponding ept entry. This patch introduces a new vcpu request named
>> KVM_REQ_APIC_PAGE_RELOAD, and makes this request to all the vcpus at this time,
>> and force all the vcpus exit guest, and re-enter guest till they updates the VMCS
>> APIC_ACCESS_ADDR pointer to the new apic access page address, and updates
>> kvm->arch.apic_access_page to the new page.
>>
>> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
>> ---
>>   arch/x86/include/asm/kvm_host.h |  1 +
>>   arch/x86/kvm/svm.c              |  6 ++++++
>>   arch/x86/kvm/vmx.c              |  6 ++++++
>>   arch/x86/kvm/x86.c              | 15 +++++++++++++++
>>   include/linux/kvm_host.h        |  2 ++
>>   virt/kvm/kvm_main.c             | 12 ++++++++++++
>>   6 files changed, 42 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 35171c7..514183e 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -739,6 +739,7 @@ struct kvm_x86_ops {
>>   	void (*hwapic_isr_update)(struct kvm *kvm, int isr);
>>   	void (*load_eoi_exitmap)(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap);
>>   	void (*set_virtual_x2apic_mode)(struct kvm_vcpu *vcpu, bool set);
>> +	void (*set_apic_access_page_addr)(struct kvm *kvm, hpa_t hpa);
>>   	void (*deliver_posted_interrupt)(struct kvm_vcpu *vcpu, int vector);
>>   	void (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
>>   	int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 1d941ad..f2eacc4 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -3619,6 +3619,11 @@ static void svm_set_virtual_x2apic_mode(struct kvm_vcpu *vcpu, bool set)
>>   	return;
>>   }
>>   
>> +static void svm_set_apic_access_page_addr(struct kvm *kvm, hpa_t hpa)
>> +{
>> +	return;
>> +}
>> +
>>   static int svm_vm_has_apicv(struct kvm *kvm)
>>   {
>>   	return 0;
>> @@ -4373,6 +4378,7 @@ static struct kvm_x86_ops svm_x86_ops = {
>>   	.enable_irq_window = enable_irq_window,
>>   	.update_cr8_intercept = update_cr8_intercept,
>>   	.set_virtual_x2apic_mode = svm_set_virtual_x2apic_mode,
>> +	.set_apic_access_page_addr = svm_set_apic_access_page_addr,
>>   	.vm_has_apicv = svm_vm_has_apicv,
>>   	.load_eoi_exitmap = svm_load_eoi_exitmap,
>>   	.hwapic_isr_update = svm_hwapic_isr_update,
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 63c4c3e..da6d55d 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -7093,6 +7093,11 @@ static void vmx_set_virtual_x2apic_mode(struct kvm_vcpu *vcpu, bool set)
>>   	vmx_set_msr_bitmap(vcpu);
>>   }
>>   
>> +static void vmx_set_apic_access_page_addr(struct kvm *kvm, hpa_t hpa)
>> +{
>> +	vmcs_write64(APIC_ACCESS_ADDR, hpa);
> This has to be guarded by "if (!is_guest_mode(vcpu))".

Since we cannot get vcpu through kvm, I'd like to move this check to
vcpu_reload_apic_access_page() when 
kvm_x86_ops->set_apic_access_page_addr()
is called.

Thanks.
>
>> +}
>> +
>>   static void vmx_hwapic_isr_update(struct kvm *kvm, int isr)
>>   {
>>   	u16 status;
>> @@ -8910,6 +8915,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
>>   	.enable_irq_window = enable_irq_window,
>>   	.update_cr8_intercept = update_cr8_intercept,
>>   	.set_virtual_x2apic_mode = vmx_set_virtual_x2apic_mode,
>> +	.set_apic_access_page_addr = vmx_set_apic_access_page_addr,
>>   	.vm_has_apicv = vmx_vm_has_apicv,
>>   	.load_eoi_exitmap = vmx_load_eoi_exitmap,
>>   	.hwapic_irr_update = vmx_hwapic_irr_update,
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index e05bd58..96f4188 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -5989,6 +5989,19 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
>>   	kvm_apic_update_tmr(vcpu, tmr);
>>   }
>>   
>> +static void vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
>> +{
>> +	/*
>> +	 * apic access page could be migrated. When the page is being migrated,
>> +	 * GUP will wait till the migrate entry is replaced with the new pte
>> +	 * entry pointing to the new page.
>> +	 */
>> +	vcpu->kvm->arch.apic_access_page = gfn_to_page(vcpu->kvm,
>> +				APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
>> +	kvm_x86_ops->set_apic_access_page_addr(vcpu->kvm,
>> +				page_to_phys(vcpu->kvm->arch.apic_access_page));
>> +}
>> +
>>   /*
>>    * Returns 1 to let __vcpu_run() continue the guest execution loop without
>>    * exiting to the userspace.  Otherwise, the value will be returned to the
>> @@ -6049,6 +6062,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>>   			kvm_deliver_pmi(vcpu);
>>   		if (kvm_check_request(KVM_REQ_SCAN_IOAPIC, vcpu))
>>   			vcpu_scan_ioapic(vcpu);
>> +		if (kvm_check_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu))
>> +			vcpu_reload_apic_access_page(vcpu);
>>   	}
>>   
>>   	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index a4c33b3..8be076a 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -136,6 +136,7 @@ static inline bool is_error_page(struct page *page)
>>   #define KVM_REQ_GLOBAL_CLOCK_UPDATE 22
>>   #define KVM_REQ_ENABLE_IBS        23
>>   #define KVM_REQ_DISABLE_IBS       24
>> +#define KVM_REQ_APIC_PAGE_RELOAD  25
>>   
>>   #define KVM_USERSPACE_IRQ_SOURCE_ID		0
>>   #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID	1
>> @@ -579,6 +580,7 @@ void kvm_flush_remote_tlbs(struct kvm *kvm);
>>   void kvm_reload_remote_mmus(struct kvm *kvm);
>>   void kvm_make_mclock_inprogress_request(struct kvm *kvm);
>>   void kvm_make_scan_ioapic_request(struct kvm *kvm);
>> +void kvm_reload_apic_access_page(struct kvm *kvm);
>>   
>>   long kvm_arch_dev_ioctl(struct file *filp,
>>   			unsigned int ioctl, unsigned long arg);
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 33712fb..d8280de 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -210,6 +210,11 @@ void kvm_make_scan_ioapic_request(struct kvm *kvm)
>>   	make_all_cpus_request(kvm, KVM_REQ_SCAN_IOAPIC);
>>   }
>>   
>> +void kvm_reload_apic_access_page(struct kvm *kvm)
>> +{
>> +	make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
>> +}
>> +
>>   int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
>>   {
>>   	struct page *page;
>> @@ -294,6 +299,13 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
>>   	if (need_tlb_flush)
>>   		kvm_flush_remote_tlbs(kvm);
>>   
>> +	/*
>> +	 * The physical address of apic access page is stroed in VMCS.
> Typo: stored, not stroed.
>
>> +	 * So need to update it when it becomes invalid.
> Please remove "so need to".
>
> Paolo
>
>> +	 */
>> +	if (address == gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT))
>> +		kvm_reload_apic_access_page(kvm);
>> +
>>   	spin_unlock(&kvm->mmu_lock);
>>   	srcu_read_unlock(&kvm->srcu, idx);
>>   }
>>
> .
>