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Subject[PATCH v9 057/105] KVM: Add functions to set GFN to private or shared
Date
From: Isaku Yamahata <isaku.yamahata@intel.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@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
arch/x86/kvm/Kconfig | 2 +-
include/linux/kvm_host.h | 17 +++++++++++-
virt/kvm/kvm_main.c | 56 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 350a921b15cb..e968ecab4d0a 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -49,7 +49,7 @@ config KVM
select SRCU
select INTERVAL_TREE
select HAVE_KVM_PM_NOTIFIER if PM
- select HAVE_KVM_PRIVATE_MEM if X86_64
+ select HAVE_KVM_PRIVATE_MEM if KVM_MMU_PRIVATE
help
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index eca3ca116412..5e11ccbc23af 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2294,9 +2294,20 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
#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, 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, unsigned int attr,
gfn_t start, gfn_t end)
{
@@ -2326,7 +2337,11 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
return !xa_load(&kvm->mem_attr_array, gfn);
}
-
+#else
+static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+ return false;
+}
#endif /* CONFIG_HAVE_KVM_PRIVATE_MEM */

#endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0dbd1734a246..20c46f26691d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1019,6 +1019,62 @@ static inline void kvm_private_mem_unregister(struct kvm_memory_slot *slot)
inaccessible_unregister_notifier(slot->private_file, &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;
+
+ /* 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)
+ kvm_arch_update_mem_attr(kvm, attr, start, gfn);
+ return r;
+}
+EXPORT_SYMBOL_GPL(kvm_vm_set_mem_attr);
+
#else /* !CONFIG_HAVE_KVM_PRIVATE_MEM */

static inline void kvm_private_mem_register(struct kvm_memory_slot *slot)
--
2.25.1
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