[PATCH v2 04/15] KVM: arm64: Fixup hyp stage-1 refcount

Quentin Perret
2021-10-19T12:13:29Z

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.

Signed-off-by: Quentin Perret <qperret@google.com>
---
arch/arm64/kvm/hyp/nvhe/setup.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index 862c7b514e20..9e5c92237a51 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -167,12 +167,22 @@ static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level,
{
enum kvm_pgtable_prot prot;
enum pkvm_page_state state;
+ struct kvm_pgtable_mm_ops *mm_ops = arg;
kvm_pte_t pte = *ptep;
phys_addr_t phys;

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;

@@ -205,7 +215,8 @@ 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,
};

return kvm_pgtable_walk(&pkvm_pgtable, 0, BIT(pkvm_pgtable.ia_bits), &walker);
@@ -230,19 +241,19 @@ 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,
- .virt_to_phys = hyp_virt_to_phys,
- .get_page = hpool_get_page,
- .put_page = hpool_put_page,
+ .zalloc_page = hyp_zalloc_hyp_page,
+ .phys_to_virt = hyp_phys_to_virt,
+ .virt_to_phys = hyp_virt_to_phys,
+ .get_page = hpool_get_page,
+ .put_page = hpool_put_page,
};
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,
--
2.33.0.1079.g6e70778dc9-goog