[PATCH] KVM: arm64: pkvm: Rollback refcount on hyp share/unshare error

[Vincent Donnefort]

If one of the HVC __pkvm_host_share_hyp or __pkvm_host_unshare_hyp fails,
rollback the refcount to ensure the hyp_shared_pfns tracking reflects
the actual sharing status.

Signed-off-by: Vincent Donnefort <vdonnefort at google.com>

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 17d64a1e11e5..0fb41d2c8b44 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -493,11 +493,17 @@ static int share_pfn_hyp(u64 pfn)
 		goto unlock;
 	}
 
+	ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp, pfn);
+	if (ret) {
+		kfree(this);
+		goto unlock;
+	}
+
 	this->pfn = pfn;
 	this->count = 1;
 	rb_link_node(&this->node, parent, node);
 	rb_insert_color(&this->node, &hyp_shared_pfns);
-	ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp, pfn);
+
 unlock:
 	mutex_unlock(&hyp_shared_pfns_lock);
 
@@ -521,9 +527,15 @@ static int unshare_pfn_hyp(u64 pfn)
 	if (this->count)
 		goto unlock;
 
+	ret = kvm_call_hyp_nvhe(__pkvm_host_unshare_hyp, pfn);
+	if (ret) {
+		this->count++;
+		goto unlock;
+	}
+
 	rb_erase(&this->node, &hyp_shared_pfns);
 	kfree(this);
-	ret = kvm_call_hyp_nvhe(__pkvm_host_unshare_hyp, pfn);
+
 unlock:
 	mutex_unlock(&hyp_shared_pfns_lock);
 

base-commit: c369299895a591d96745d6492d4888259b004a9e
-- 
2.53.0.1018.g2bb0e51243-goog