kvm: x86: Unpin and remove kvm_arch->apic_access_page
In order to make the APIC access page migratable, stop pinning it in
memory.
And because the APIC access page is not pinned in memory, we can
remove kvm_arch->apic_access_page. When we need to write its
physical address into vmcs, we use gfn_to_page() to get its page
struct, which is needed to call page_to_phys(); the page is then
immediately unpinned.
Suggested-by: Gleb Natapov <gleb@kernel.org>
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 60f9d73..7d603a7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -574,7 +574,7 @@
struct kvm_apic_map *apic_map;
unsigned int tss_addr;
- struct page *apic_access_page;
+ bool apic_access_page_done;
gpa_t wall_clock;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 881d266..04fa1b8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4033,7 +4033,7 @@
int r = 0;
mutex_lock(&kvm->slots_lock);
- if (kvm->arch.apic_access_page)
+ if (kvm->arch.apic_access_page_done)
goto out;
kvm_userspace_mem.slot = APIC_ACCESS_PAGE_PRIVATE_MEMSLOT;
kvm_userspace_mem.flags = 0;
@@ -4049,7 +4049,12 @@
goto out;
}
- kvm->arch.apic_access_page = page;
+ /*
+ * Do not pin the page in memory, so that memory hot-unplug
+ * is able to migrate it.
+ */
+ put_page(page);
+ kvm->arch.apic_access_page_done = true;
out:
mutex_unlock(&kvm->slots_lock);
return r;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c1412f5..6857257 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6028,19 +6028,31 @@
void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
{
+ struct page *page = NULL;
+
if (!kvm_x86_ops->set_apic_access_page_addr)
return;
- 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,
- page_to_phys(vcpu->kvm->arch.apic_access_page));
+ page = gfn_to_page(vcpu->kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
+ kvm_x86_ops->set_apic_access_page_addr(vcpu, page_to_phys(page));
+
+ /*
+ * Do not pin apic access page in memory, the MMU notifier
+ * will call us again if it is migrated or swapped out.
+ */
+ put_page(page);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_reload_apic_access_page);
void kvm_arch_mmu_notifier_invalidate_page(struct kvm *kvm,
unsigned long address)
{
+ /*
+ * The physical address of apic access page is stored in the VMCS.
+ * Update it when it becomes invalid.
+ */
+ if (address == gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT))
+ kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
}
/*
@@ -7297,8 +7309,6 @@
kfree(kvm->arch.vpic);
kfree(kvm->arch.vioapic);
kvm_free_vcpus(kvm);
- if (kvm->arch.apic_access_page)
- put_page(kvm->arch.apic_access_page);
kfree(rcu_dereference_check(kvm->arch.apic_map, 1));
}