[PATCH 02/27] KVM: x86/mmu: Factor out helper to get max mapping size of a memslot

Sean Christopherson
2022-12-23T00:58:02Z

Extract the memslot-related logic of kvm_mmu_max_mapping_level() into a
new helper so that KVMGT can determine whether or not mapping a 2MiB page
into the guest is (dis)allowed per KVM's memslots.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/mmu.c | 21 +++++++++++++++------
arch/x86/kvm/mmu/mmu_internal.h | 2 ++
2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 254bc46234e0..ca7428b68eba 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3064,20 +3064,29 @@ static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn,
return level;
}

+int kvm_mmu_max_slot_mapping_level(const struct kvm_memory_slot *slot,
+ gfn_t gfn, int max_level)
+{
+ struct kvm_lpage_info *linfo;
+
+ for ( ; max_level > PG_LEVEL_4K; max_level--) {
+ linfo = lpage_info_slot(gfn, slot, max_level);
+ if (!linfo->disallow_lpage)
+ break;
+ }
+ return max_level;
+}
+
int kvm_mmu_max_mapping_level(struct kvm *kvm,
const struct kvm_memory_slot *slot, gfn_t gfn,
int max_level)
{
- struct kvm_lpage_info *linfo;
int host_level;

max_level = min(max_level, max_huge_page_level);
- for ( ; max_level > PG_LEVEL_4K; max_level--) {
- linfo = lpage_info_slot(gfn, slot, max_level);
- if (!linfo->disallow_lpage)
- break;
- }
+ max_level = kvm_mmu_max_slot_mapping_level(slot, gfn, max_level);

+ /* Avoid walking the host page tables if a hugepage is impossible. */
if (max_level == PG_LEVEL_4K)
return PG_LEVEL_4K;

diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index ac00bfbf32f6..b078c29e5674 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -314,6 +314,8 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
return r;
}

+int kvm_mmu_max_slot_mapping_level(const struct kvm_memory_slot *slot,
+ gfn_t gfn, int max_level);
int kvm_mmu_max_mapping_level(struct kvm *kvm,
const struct kvm_memory_slot *slot, gfn_t gfn,
int max_level);
--
2.39.0.314.g84b9a713c41-goog