[PATCH v2 3/5] KVM: Add a dedicated API for setting KVM-internal memslots

Sean Christopherson
2025-01-11T00:20:30Z

Add a dedicated API for setting internal memslots, and have it explicitly
disallow setting userspace memslots. Setting a userspace memslots without
a direct command from userspace would result in all manner of issues.

No functional change intended.

Cc: Tao Su <tao1.su@linux.intel.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 2 +-
include/linux/kvm_host.h | 4 ++--
virt/kvm/kvm_main.c | 15 ++++++++++++---
3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a861287a67bd..36b5d06e3904 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12827,7 +12827,7 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
m.guest_phys_addr = gpa;
m.userspace_addr = hva;
m.memory_size = size;
- r = __kvm_set_memory_region(kvm, &m);
+ r = kvm_set_internal_memslot(kvm, &m);
if (r < 0)
return ERR_PTR_USR(r);
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7443de24b1d9..8707d25a2e5b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1192,8 +1192,8 @@ enum kvm_mr_change {
KVM_MR_FLAGS_ONLY,
};

-int __kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region2 *mem);
+int kvm_set_internal_memslot(struct kvm *kvm,
+ const struct kvm_userspace_memory_region2 *mem);
void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);
int kvm_arch_prepare_memory_region(struct kvm *kvm,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7d25b50cb298..e1be2e4e6c9f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1926,8 +1926,8 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
return false;
}

-int __kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region2 *mem)
+static int __kvm_set_memory_region(struct kvm *kvm,
+ const struct kvm_userspace_memory_region2 *mem)
{
struct kvm_memory_slot *old, *new;
struct kvm_memslots *slots;
@@ -2050,7 +2050,16 @@ int __kvm_set_memory_region(struct kvm *kvm,
kfree(new);
return r;
}
-EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
+
+int kvm_set_internal_memslot(struct kvm *kvm,
+ const struct kvm_userspace_memory_region2 *mem)
+{
+ if (WARN_ON_ONCE(mem->slot < KVM_USER_MEM_SLOTS))
+ return -EINVAL;
+
+ return __kvm_set_memory_region(kvm, mem);
+}
+EXPORT_SYMBOL_GPL(kvm_set_internal_memslot);

static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
struct kvm_userspace_memory_region2 *mem)
--
2.47.1.613.gc27f4b7a9f-goog