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Subject[PATCH v4 03/14] KVM: arm64: Fixup hyp stage-1 refcount
From
In nVHE-protected mode, the hyp stage-1 page-table refcount is broken
due to the lack of refcount support in the early allocator. Fix-up the
refcount in the finalize walker, once the 'hyp_vmemmap' is up and running.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
arch/arm64/kvm/hyp/nvhe/setup.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index e31149965204..ab44e004e6d3 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -166,6 +166,7 @@ static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level,
enum kvm_pgtable_walk_flags flag,
void * const arg)
{
+ struct kvm_pgtable_mm_ops *mm_ops = arg;
enum kvm_pgtable_prot prot;
enum pkvm_page_state state;
kvm_pte_t pte = *ptep;
@@ -174,6 +175,15 @@ static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level,
if (!kvm_pte_valid(pte))
return 0;

+ /*
+ * Fix-up the refcount for the page-table pages as the early allocator
+ * was unable to access the hyp_vmemmap and so the buddy allocator has
+ * initialised the refcount to '1'.
+ */
+ mm_ops->get_page(ptep);
+ if (flag != KVM_PGTABLE_WALK_LEAF)
+ return 0;
+
if (level != (KVM_PGTABLE_MAX_LEVELS - 1))
return -EINVAL;

@@ -206,7 +216,8 @@ static int finalize_host_mappings(void)
{
struct kvm_pgtable_walker walker = {
.cb = finalize_host_mappings_walker,
- .flags = KVM_PGTABLE_WALK_LEAF,
+ .flags = KVM_PGTABLE_WALK_LEAF | KVM_PGTABLE_WALK_TABLE_POST,
+ .arg = pkvm_pgtable.mm_ops,
};
int i, ret;

@@ -241,10 +252,6 @@ void __noreturn __pkvm_init_finalise(void)
if (ret)
goto out;

- ret = finalize_host_mappings();
- if (ret)
- goto out;
-
pkvm_pgtable_mm_ops = (struct kvm_pgtable_mm_ops) {
.zalloc_page = hyp_zalloc_hyp_page,
.phys_to_virt = hyp_phys_to_virt,
@@ -254,6 +261,10 @@ void __noreturn __pkvm_init_finalise(void)
};
pkvm_pgtable.mm_ops = &pkvm_pgtable_mm_ops;

+ ret = finalize_host_mappings();
+ if (ret)
+ goto out;
+
out:
/*
* We tail-called to here from handle___pkvm_init() and will not return,
--
2.34.1.173.g76aa8bc2d0-goog
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