Explicit disallow activating a gfn_to_pfn_cache with an error gpa, i.e.
INVALID_GPA, to ensure that KVM doesn't mistake a GPA-based cache for an
HVA-based cache (KVM uses INVALID_GPA as a magic value to differentiate
between GPA-based and HVA-based caches).
WARN if KVM attempts to activate a cache with INVALID_GPA, purely so that
new caches need to at least consider what to do with a "bad" GPA, as all
existing usage of kvm_gpc_activate() guarantees gpa != INVALID_GPA. I.e.
removing the WARN in the future is completely reasonable if doing so would
yield cleaner/better code overall.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
virt/kvm/pfncache.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 91b0e329006b..f618719644e0 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -418,6 +418,13 @@ static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned
int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)
{
+ /*
+ * Explicitly disallow INVALID_GPA so that the magic value can be used
+ * by KVM to differentiate between GPA-based and HVA-based caches.
+ */
+ if (WARN_ON_ONCE(kvm_is_error_gpa(gpa)))
+ return -EINVAL;
+
return __kvm_gpc_activate(gpc, gpa, KVM_HVA_ERR_BAD, len);
}
--
2.44.0.291.gc1ea87d7ee-goog
