On 17/07/21 11:55, Marc Zyngier wrote:
We currently rely on the kvm_is_transparent_hugepage() helper to
discover whether a given page has the potential to be mapped as
a block mapping.
However, this API doesn't really give un everything we want:
- we don't get the size: this is not crucial today as we only
support PMD-sized THPs, but we'd like to have larger sizes
in the future
- we're the only user left of the API, and there is a will
to remove it altogether
To address the above, implement a simple walker using the existing
page table infrastructure, and plumb it into transparent_hugepage_adjust().
No new page sizes are supported in the process.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
If it's okay for you to reuse the KVM page walker that's fine of course,
but the arch/x86/mm functions lookup_address_in_{mm,pgd} are mostly
machine-independent and it may make sense to move them to mm/.
That would also allow reusing the x86 function host_pfn_mapping_level.
Paolo
---
arch/arm64/kvm/mmu.c | 46 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 42 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 3155c9e778f0..db6314b93e99 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -433,6 +433,44 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
return 0;
}
+static struct kvm_pgtable_mm_ops kvm_user_mm_ops = {
+ /* We shouldn't need any other callback to walk the PT */
+ .phys_to_virt = kvm_host_va,
+};
+
+struct user_walk_data {
+ u32 level;
+};
+
+static int user_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
+ enum kvm_pgtable_walk_flags flag, void * const arg)
+{
+ struct user_walk_data *data = arg;
+
+ data->level = level;
+ return 0;
+}
+
+static int get_user_mapping_size(struct kvm *kvm, u64 addr)
+{
+ struct user_walk_data data;
+ struct kvm_pgtable pgt = {
+ .pgd = (kvm_pte_t *)kvm->mm->pgd,
+ .ia_bits = VA_BITS,
+ .start_level = 4 - CONFIG_PGTABLE_LEVELS,
+ .mm_ops = &kvm_user_mm_ops,
+ };
+ struct kvm_pgtable_walker walker = {
+ .cb = user_walker,
+ .flags = KVM_PGTABLE_WALK_LEAF,
+ .arg = &data,
+ };
+
+ kvm_pgtable_walk(&pgt, ALIGN_DOWN(addr, PAGE_SIZE), PAGE_SIZE, &walker);
+
+ return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(data.level));
+}
+
static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
.zalloc_page = stage2_memcache_zalloc_page,
.zalloc_pages_exact = kvm_host_zalloc_pages_exact,
@@ -780,7 +818,7 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
* Returns the size of the mapping.
*/
static unsigned long
-transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
+transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot,
unsigned long hva, kvm_pfn_t *pfnp,
phys_addr_t *ipap)
{
@@ -791,8 +829,8 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
* sure that the HVA and IPA are sufficiently aligned and that the
* block map is contained within the memslot.
*/
- if (kvm_is_transparent_hugepage(pfn) &&
- fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
+ if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) &&
+ get_user_mapping_size(kvm, hva) >= PMD_SIZE) {
/*
* The address we faulted on is backed by a transparent huge
* page. However, because we map the compound huge page and
@@ -1051,7 +1089,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* backed by a THP and thus use block mapping if possible.
*/
if (vma_pagesize == PAGE_SIZE && !(force_pte || device))
- vma_pagesize = transparent_hugepage_adjust(memslot, hva,
+ vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva,
&pfn, &fault_ipa);
if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
