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Subject[PATCH 3/4] kvm, memory-hotplug: Update ept identity pagetable when it is migrated.
Date
ept identity pagetable is pinned in memory, and as a result it cannot be
migrated/hot-removed.

But actually it doesn't need to be pinned in memory.

This patch introduces a new vcpu request: KVM_REQ_MIGRATE_EPT to reset ept
indetity pagetable related variable. This request will be made when
kvm_mmu_notifier_invalidate_page() is called when the page is unmapped
from the qemu user space to reset kvm->arch.ept_identity_pagetable to NULL.
And will also be made when ept violation happens to reset
kvm->arch.ept_identity_pagetable to the new page.
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 11 +++++++++++
arch/x86/kvm/vmx.c | 3 ++-
arch/x86/kvm/x86.c | 16 ++++++++++++++++
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 6 ++++++
6 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4931415..8771c0f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -581,6 +581,7 @@ struct kvm_arch {
struct page *ept_identity_pagetable;
bool ept_identity_pagetable_done;
gpa_t ept_identity_map_addr;
+ bool ept_identity_pagetable_migrated;

unsigned long irq_sources_bitmap;
s64 kvmclock_offset;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9314678..c0d72f6 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3425,6 +3425,17 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
transparent_hugepage_adjust(vcpu, &gfn, &pfn, &level);
r = __direct_map(vcpu, gpa, write, map_writable,
level, gfn, pfn, prefault);
+
+ /*
+ * Update ept identity pagetable page and apic access page if
+ * they are migrated.
+ */
+ if (gpa == vcpu->kvm->arch.ept_identity_map_addr &&
+ vcpu->kvm->arch.ept_identity_pagetable_migrated) {
+ vcpu->kvm->arch.ept_identity_pagetable_migrated = false;
+ kvm_make_request(KVM_REQ_MIGRATE_EPT, vcpu);
+ }
+
spin_unlock(&vcpu->kvm->mmu_lock);

return r;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 366b5b3..c336cb3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4018,7 +4018,8 @@ static int alloc_identity_pagetable(struct kvm *kvm)
if (r)
goto out;

- page = gfn_to_page(kvm, kvm->arch.ept_identity_map_addr >> PAGE_SHIFT);
+ page = gfn_to_page_no_pin(kvm,
+ kvm->arch.ept_identity_map_addr >> PAGE_SHIFT);
if (is_error_page(page)) {
r = -EFAULT;
goto out;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f32a025..a26524f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5929,6 +5929,20 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
kvm_apic_update_tmr(vcpu, tmr);
}

+static void vcpu_migrated_page_update_ept(struct kvm_vcpu *vcpu)
+{
+ struct kvm *kvm = vcpu->kvm;
+
+ if (kvm->arch.ept_identity_pagetable_migrated)
+ kvm->arch.ept_identity_pagetable = NULL;
+ else {
+ struct page *page;
+ page = gfn_to_page_no_pin(kvm,
+ kvm->arch.ept_identity_map_addr >> PAGE_SHIFT);
+ kvm->arch.ept_identity_pagetable = 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
@@ -5989,6 +6003,8 @@ 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_MIGRATE_EPT, vcpu))
+ vcpu_migrated_page_update_ept(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 7c58d9d..4b7e51a 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_MIGRATE_EPT 25

#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 6091849..d271e89 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -294,6 +294,12 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
if (need_tlb_flush)
kvm_flush_remote_tlbs(kvm);

+ if (address ==
+ gfn_to_hva(kvm, kvm->arch.ept_identity_map_addr >> PAGE_SHIFT)) {
+ kvm->arch.ept_identity_pagetable_migrated = true;
+ kvm_make_request(KVM_REQ_MIGRATE_EPT, kvm->vcpus[0]);
+ }
+
spin_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, idx);
}
--
1.8.3.1


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