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

Tang Chen
2014-09-11T05:37:03Z

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);
+}
+
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.
+ * So need to update it when it becomes invalid.
+ */
+ 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);
}
--
1.8.3.1