[PATCH 6/6] KVM: arm64: Fix initialisation order in __pkvm_init_finalise()

[Fuad Tabba]

From: Quentin Perret <qperret at google.com>

fix_host_ownership() walks the hypervisor's stage-1 page-table to
adjust the host's stage-2 accordingly. Any such adjustment that
requires cache maintenance operations depends on the per-CPU hyp
fixmap being present. However, fix_host_ownership() is currently
called before fix_hyp_pgtable_refcnt() and hyp_create_fixmap(), so
the fixmap does not yet exist when it runs.

This is benign today because the host stage-2 starts empty and no
CMOs are needed, but it becomes a latent crash as soon as
fix_host_ownership() is extended to operate on a non-empty
page-table.

Reorder the calls so that fix_hyp_pgtable_refcnt() and
hyp_create_fixmap() complete before fix_host_ownership() is invoked.

Fixes: 0d16d12eb26e ("KVM: arm64: Fix-up hyp stage-1 refcounts for all pages mapped at EL2")
Signed-off-by: Quentin Perret <qperret at google.com>
Signed-off-by: Fuad Tabba <tabba at google.com>
---
 arch/arm64/kvm/hyp/nvhe/setup.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index d8e5b563fd3d..d461981616d9 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -312,10 +312,6 @@ void __noreturn __pkvm_init_finalise(void)
 	};
 	pkvm_pgtable.mm_ops = &pkvm_pgtable_mm_ops;
 
-	ret = fix_host_ownership();
-	if (ret)
-		goto out;
-
 	ret = fix_hyp_pgtable_refcnt();
 	if (ret)
 		goto out;
@@ -324,6 +320,10 @@ void __noreturn __pkvm_init_finalise(void)
 	if (ret)
 		goto out;
 
+	ret = fix_host_ownership();
+	if (ret)
+		goto out;
+
 	ret = hyp_ffa_init(ffa_proxy_pages);
 	if (ret)
 		goto out;
-- 
2.54.0.rc2.544.gc7ae2d5bb8-goog