KVM: Add a dedicated API for setting KVM-internal memslots

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>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Link: https://lore.kernel.org/r/20250111002022.1230573-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a861287a67bd46ef9ab8f5d73c470801a9ed4b62..36b5d06e39045156ae4b249c692be8a736b944f3 100644 (file)
--- 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 7443de24b1d98ade0d1ce080ca82c12ed074b633..8707d25a2e5ba19e8c570b0bf4c84acf86b77b94 100644 (file)
--- 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 7d25b50cb298a8c64d8a2957a0e4377db5c059c5..e1be2e4e6c9f021fce03794fce17e3039f86e1c1 100644 (file)
--- 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 @@ out:
        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)