Re: [PATCH 4/4] kvm, mem-hotplug: Update apic access page when it is migrated.

[Wanpeng Li]

On Wed, Jul 02, 2014 at 05:00:37PM +0800, Tang Chen wrote:
>apic access page is pinned in memory, and as a result it cannot be
>migrated/hot-removed.
>
>Actually it doesn't need to be pinned in memory.
>
>This patch introduces a new vcpu request: KVM_REQ_MIGRATE_EPT. This requet

s/KVM_REQ_MIGRATE_EPT/KVM_REQ_MIGRATE_APIC

>will be made when kvm_mmu_notifier_invalidate_page() is called when the page
>is unmapped from the qemu user space to reset APIC_ACCESS_ADDR pointer in
>each online vcpu to 0. And will also be made when ept violation happens to
>reset APIC_ACCESS_ADDR to the new page phys_addr (host phys_addr).
>---
> arch/x86/include/asm/kvm_host.h |  2 ++
> arch/x86/kvm/mmu.c              | 15 +++++++++++++++
> arch/x86/kvm/vmx.c              |  9 ++++++++-
> arch/x86/kvm/x86.c              | 20 ++++++++++++++++++++
> include/linux/kvm_host.h        |  1 +
> virt/kvm/kvm_main.c             | 15 +++++++++++++++
> 6 files changed, 61 insertions(+), 1 deletion(-)
>
>diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>index 8771c0f..f104b87 100644
>--- a/arch/x86/include/asm/kvm_host.h
>+++ b/arch/x86/include/asm/kvm_host.h
>@@ -575,6 +575,7 @@ struct kvm_arch {
> 
> 	unsigned int tss_addr;
> 	struct page *apic_access_page;
>+	bool apic_access_page_migrated;
> 
> 	gpa_t wall_clock;
> 
>@@ -739,6 +740,7 @@ 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/mmu.c b/arch/x86/kvm/mmu.c
>index c0d72f6..a655444 100644
>--- a/arch/x86/kvm/mmu.c
>+++ b/arch/x86/kvm/mmu.c
>@@ -3436,6 +3436,21 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
> 		kvm_make_request(KVM_REQ_MIGRATE_EPT, vcpu);
> 	}
> 
>+	if (gpa == VMX_APIC_ACCESS_PAGE_ADDR &&
>+	    vcpu->kvm->arch.apic_access_page_migrated) {
>+		int i;
>+
>+		vcpu->kvm->arch.apic_access_page_migrated = false;
>+
>+		/*
>+		 * We need update APIC_ACCESS_ADDR pointer in each VMCS of
>+		 * all the online vcpus.
>+		 */
>+		for (i = 0; i < atomic_read(&vcpu->kvm->online_vcpus); i++)
>+			kvm_make_request(KVM_REQ_MIGRATE_APIC,
>+					 vcpu->kvm->vcpus[i]);
>+	}
>+
> 	spin_unlock(&vcpu->kvm->mmu_lock);
> 
> 	return r;
>diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>index c336cb3..abc152f 100644
>--- a/arch/x86/kvm/vmx.c
>+++ b/arch/x86/kvm/vmx.c
>@@ -3988,7 +3988,7 @@ static int alloc_apic_access_page(struct kvm *kvm)
> 	if (r)
> 		goto out;
> 
>-	page = gfn_to_page(kvm, VMX_APIC_ACCESS_PAGE_ADDR >> PAGE_SHIFT);
>+	page = gfn_to_page_no_pin(kvm, VMX_APIC_ACCESS_PAGE_ADDR >> PAGE_SHIFT);
> 	if (is_error_page(page)) {
> 		r = -EFAULT;
> 		goto out;
>@@ -7075,6 +7075,12 @@ 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)
>+{
>+	if (vm_need_virtualize_apic_accesses(kvm))
>+		vmcs_write64(APIC_ACCESS_ADDR, hpa);
>+}
>+
> static void vmx_hwapic_isr_update(struct kvm *kvm, int isr)
> {
> 	u16 status;
>@@ -8846,6 +8852,7 @@ 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 a26524f..14e7174 100644
>--- a/arch/x86/kvm/x86.c
>+++ b/arch/x86/kvm/x86.c
>@@ -5943,6 +5943,24 @@ static void vcpu_migrated_page_update_ept(struct kvm_vcpu *vcpu)
> 	}
> }
> 
>+static void vcpu_migrated_page_update_apic(struct kvm_vcpu *vcpu)
>+{
>+	struct kvm *kvm = vcpu->kvm;
>+
>+	if (kvm->arch.apic_access_page_migrated) {
>+		if (kvm->arch.apic_access_page)
>+			kvm->arch.apic_access_page = pfn_to_page(0);
>+		kvm_x86_ops->set_apic_access_page_addr(kvm, 0x0ull);
>+	} else {
>+		struct page *page;
>+		page = gfn_to_page_no_pin(kvm,
>+				VMX_APIC_ACCESS_PAGE_ADDR >> PAGE_SHIFT);
>+		kvm->arch.apic_access_page = page;
>+		kvm_x86_ops->set_apic_access_page_addr(kvm,
>+						       page_to_phys(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
>@@ -6005,6 +6023,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> 			vcpu_scan_ioapic(vcpu);
> 		if (kvm_check_request(KVM_REQ_MIGRATE_EPT, vcpu))
> 			vcpu_migrated_page_update_ept(vcpu);
>+		if (kvm_check_request(KVM_REQ_MIGRATE_APIC, vcpu))
>+			vcpu_migrated_page_update_apic(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 4b7e51a..e2ad65e 100644
>--- a/include/linux/kvm_host.h
>+++ b/include/linux/kvm_host.h
>@@ -137,6 +137,7 @@ static inline bool is_error_page(struct page *page)
> #define KVM_REQ_ENABLE_IBS        23
> #define KVM_REQ_DISABLE_IBS       24
> #define KVM_REQ_MIGRATE_EPT       25
>+#define KVM_REQ_MIGRATE_APIC      26
> 
> #define KVM_USERSPACE_IRQ_SOURCE_ID		0
> #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID	1
>diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>index d271e89..f06438c 100644
>--- a/virt/kvm/kvm_main.c
>+++ b/virt/kvm/kvm_main.c
>@@ -54,6 +54,7 @@
> #include <asm/io.h>
> #include <asm/uaccess.h>
> #include <asm/pgtable.h>
>+#include <asm/vmx.h>
> 
> #include "coalesced_mmio.h"
> #include "async_pf.h"
>@@ -300,6 +301,20 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
> 		kvm_make_request(KVM_REQ_MIGRATE_EPT, kvm->vcpus[0]);
> 	}
> 
>+	if (address ==
>+	    gfn_to_hva(kvm, VMX_APIC_ACCESS_PAGE_ADDR >> PAGE_SHIFT)) {
>+		int i;
>+
>+		kvm->arch.apic_access_page_migrated = true;
>+
>+		/*
>+		 * We need update APIC_ACCESS_ADDR pointer in each VMCS of
>+		 * all the online vcpus.
>+		 */
>+		for (i = 0; i < atomic_read(&kvm->online_vcpus); i++)
>+			kvm_make_request(KVM_REQ_MIGRATE_APIC, kvm->vcpus[i]);
>+	}
>+
> 	spin_unlock(&kvm->mmu_lock);
> 	srcu_read_unlock(&kvm->srcu, idx);
> }
>-- 
>1.8.3.1
>
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