linux-kernel - [PATCH v10 060/108] KVM: Add functions to set GFN to private or shared

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Date:   Sat, 29 Oct 2022 23:23:01 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: [PATCH v10 060/108] KVM: Add functions to set GFN to private or shared

From: Isaku Yamahata <isaku.yamahata@...el.com>

TDX KVM support needs to track whether GFN is private or shared.  Introduce
functions to set whether GFN is private or shared and pre-allocate memory
for xarray.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 include/linux/kvm_host.h | 11 ++++++
 virt/kvm/kvm_main.c      | 74 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a0b64308d240..fac07886ab39 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2307,9 +2307,20 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
 #define KVM_MEM_ATTR_PRIVATE	0x0002
 
 #ifdef __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
+/* memory attr on [start, end) */
+int kvm_vm_reserve_mem_attr(struct kvm *kvm, gfn_t start, gfn_t end);
+int kvm_vm_set_mem_attr(struct kvm *kvm, int attr, gfn_t start, gfn_t end);
 void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot,
 			      unsigned int attr, gfn_t start, gfn_t end);
 #else
+static inline int kvm_vm_reserve_mem_attr(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+	return -EOPNOTSUPP;
+}
+static inline int kvm_vm_set_mem_attr(struct kvm *kvm, int attr, gfn_t start, gfn_t end)
+{
+	return -EOPNOTSUPP;
+}
 static inline void kvm_arch_update_mem_attr(struct kvm *kvm,
 					    struct kvm_memory_slot *slot,
 					    unsigned int attr,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9f82b03a8118..f0e77b65939b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1121,6 +1121,80 @@ static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
 					  &slot->notifier);
 }
 
+/*
+ * Reserve memory for [start, end) so that the next set oepration won't fail
+ * with -ENOMEM.
+ */
+int kvm_vm_reserve_mem_attr(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+	int r = 0;
+	gfn_t gfn;
+
+	xa_lock(&kvm->mem_attr_array);
+	for (gfn = start; gfn < end; gfn++) {
+		r = __xa_insert(&kvm->mem_attr_array, gfn, NULL, GFP_KERNEL_ACCOUNT);
+		if (r == -EBUSY)
+			r = 0;
+		if (r)
+			break;
+	}
+	xa_unlock(&kvm->mem_attr_array);
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(kvm_vm_reserve_mem_attr);
+
+/* Set memory attr for [start, end) */
+int kvm_vm_set_mem_attr(struct kvm *kvm, int attr, gfn_t start, gfn_t end)
+{
+	void *entry;
+	gfn_t gfn;
+	int r;
+	int i;
+
+	/* By default, the entry is private. */
+	switch (attr) {
+	case KVM_MEM_ATTR_PRIVATE:
+		entry = NULL;
+		break;
+	case KVM_MEM_ATTR_SHARED:
+		entry = xa_mk_value(KVM_MEM_ATTR_SHARED);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return -EINVAL;
+	}
+
+	WARN_ON_ONCE(start >= end);
+	for (gfn = start; gfn < end; gfn++) {
+		r = xa_err(xa_store(&kvm->mem_attr_array, gfn, entry,
+				    GFP_KERNEL_ACCOUNT));
+		if (r)
+			break;
+	}
+	if (start >= gfn)
+		return r;
+
+	end = gfn;
+	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+		struct kvm_memslot_iter iter;
+		struct kvm_memory_slot *slot;
+		struct kvm_memslots *slots;
+
+		slots = __kvm_memslots(kvm, i);
+		kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
+			gfn_t s = max(start, slot->base_gfn);
+			gfn_t e = min(end, slot->base_gfn + slot->npages);
+
+			WARN_ON_ONCE(s >= e);
+			kvm_arch_update_mem_attr(kvm, slot, attr, s, e);
+		}
+	}
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(kvm_vm_set_mem_attr);
+
 #else /* !CONFIG_HAVE_KVM_RESTRICTED_MEM */
 
 static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
-- 
2.25.1