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Subject[RFC V2 6/9] Apply the direct build EPT according to the memory slots change
Date
From: Yulei Zhang <yulei.kernel@gmail.com>

Construct the direct build ept when guest memory slots have been
changed, and issue mmu_reload request to update the CR3 so that
guest could use the pre-constructed EPT without page fault.

Signed-off-by: Yulei Zhang <yuleixzhang@tencent.com>
---
arch/mips/kvm/mips.c | 13 +++++++++++++
arch/powerpc/kvm/powerpc.c | 13 +++++++++++++
arch/s390/kvm/kvm-s390.c | 13 +++++++++++++
arch/x86/kvm/mmu/mmu.c | 33 ++++++++++++++++++++++++++-------
include/linux/kvm_host.h | 3 +++
virt/kvm/kvm_main.c | 13 +++++++++++++
6 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 7de85d2253ff..05d053a53ebf 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -267,6 +267,19 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
}
}

+int kvm_direct_tdp_populate_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 0;
+}
+
+void kvm_direct_tdp_remove_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+}
+
+void kvm_direct_tdp_release_global_root(struct kvm *kvm)
+{
+}
+
static inline void dump_handler(const char *symbol, void *start, void *end)
{
u32 *p;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 13999123b735..c6964cbeb6da 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -715,6 +715,19 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
kvmppc_core_commit_memory_region(kvm, mem, old, new, change);
}

+int kvm_direct_tdp_populate_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 0;
+}
+
+void kvm_direct_tdp_remove_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+}
+
+void kvm_direct_tdp_release_global_root(struct kvm *kvm)
+{
+}
+
void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6b74b92c1a58..d6f7cf1a30a3 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5021,6 +5021,19 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
return;
}

+int kvm_direct_tdp_populate_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ return 0;
+}
+
+void kvm_direct_tdp_remove_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+}
+
+void kvm_direct_tdp_release_global_root(struct kvm *kvm)
+{
+}
+
static inline unsigned long nonhyp_mask(int i)
{
unsigned int nonhyp_fai = (sclp.hmfai << i * 2) >> 30;
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index fda6c4196854..47d2a1c18f36 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5206,13 +5206,20 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
{
int r;

- r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->direct_map);
- if (r)
- goto out;
- r = mmu_alloc_roots(vcpu);
- kvm_mmu_sync_roots(vcpu);
- if (r)
- goto out;
+ if (vcpu->kvm->arch.global_root_hpa) {
+ vcpu->arch.direct_build_tdp = true;
+ vcpu->arch.mmu->root_hpa = vcpu->kvm->arch.global_root_hpa;
+ }
+
+ if (!vcpu->arch.direct_build_tdp) {
+ r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->direct_map);
+ if (r)
+ goto out;
+ r = mmu_alloc_roots(vcpu);
+ kvm_mmu_sync_roots(vcpu);
+ if (r)
+ goto out;
+ }
kvm_mmu_load_pgd(vcpu);
kvm_x86_ops.tlb_flush_current(vcpu);
out:
@@ -6464,6 +6471,17 @@ int direct_build_mapping_level(struct kvm *kvm, struct kvm_memory_slot *slot, gf
return host_level;
}

+static void kvm_make_direct_build_update(struct kvm *kvm)
+{
+ int i;
+ struct kvm_vcpu *vcpu;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
+ kvm_vcpu_kick(vcpu);
+ }
+}
+
int kvm_direct_tdp_populate_page_table(struct kvm *kvm, struct kvm_memory_slot *slot)
{
gfn_t gfn;
@@ -6498,6 +6516,7 @@ int kvm_direct_tdp_populate_page_table(struct kvm *kvm, struct kvm_memory_slot *
direct_build_tdp_map(kvm, slot, gfn, pfn, host_level);
}

+ kvm_make_direct_build_update(kvm);
return 0;
}

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8901862ba2a3..b2aa0daad6dd 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -694,6 +694,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
struct kvm_memory_slot *old,
const struct kvm_memory_slot *new,
enum kvm_mr_change change);
+int kvm_direct_tdp_populate_page_table(struct kvm *kvm, struct kvm_memory_slot *slot);
+void kvm_direct_tdp_remove_page_table(struct kvm *kvm, struct kvm_memory_slot *slot);
+void kvm_direct_tdp_release_global_root(struct kvm *kvm);
void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot, gfn_t gfn);
/* flush all memory translations */
void kvm_arch_flush_shadow_all(struct kvm *kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 47fc18b05c53..fd1b419f4eb4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -876,6 +876,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
#endif
kvm_arch_destroy_vm(kvm);
kvm_destroy_devices(kvm);
+ kvm_direct_tdp_release_global_root(kvm);
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
kvm_free_memslots(kvm, __kvm_memslots(kvm, i));
cleanup_srcu_struct(&kvm->irq_srcu);
@@ -1195,6 +1196,10 @@ static int kvm_set_memslot(struct kvm *kvm,
* in the freshly allocated memslots, not in @old or @new.
*/
slot = id_to_memslot(slots, old->id);
+ /* Remove pre-constructed page table */
+ if (!as_id)
+ kvm_direct_tdp_remove_page_table(kvm, slot);
+
slot->flags |= KVM_MEMSLOT_INVALID;

/*
@@ -1222,6 +1227,14 @@ static int kvm_set_memslot(struct kvm *kvm,
update_memslots(slots, new, change);
slots = install_new_memslots(kvm, as_id, slots);

+ if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
+ if (!as_id) {
+ r = kvm_direct_tdp_populate_page_table(kvm, new);
+ if (r)
+ goto out_slots;
+ }
+ }
+
kvm_arch_commit_memory_region(kvm, mem, old, new, change);

kvfree(slots);
--
2.17.1
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