[PATCH v2 5/5] KVM: Disallow all flags for KVM-internal memslots

Sean Christopherson
2025-01-11T00:20:33Z

Disallow all flags for KVM-internal memslots as all existing flags require
some amount of userspace interaction to have any meaning. In addition to
guarding against KVM goofs, explicitly disallowing dirty logging of KVM-
internal memslots will (hopefully) allow exempting KVM-internal memslots
from the KVM_MEM_MAX_NR_PAGES limit, which appears to exist purely because
the dirty bitmap operations use a 32-bit index.

Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
virt/kvm/kvm_main.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ecd4a66b22f3..a8a84bf450f9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2057,6 +2057,9 @@ int kvm_set_internal_memslot(struct kvm *kvm,
if (WARN_ON_ONCE(mem->slot < KVM_USER_MEM_SLOTS))
return -EINVAL;

+ if (WARN_ON_ONCE(mem->flags))
+ return -EINVAL;
+
return kvm_set_memory_region(kvm, mem);
}
EXPORT_SYMBOL_GPL(kvm_set_internal_memslot);
--
2.47.1.613.gc27f4b7a9f-goog