[PATCH 1/6] KVM: arm64: Add __gmem_abort and __user_mem_abort

Jack Thomson
2025-09-11T13:49:42Z

Adding __gmem_abort and __user_mem_abort that preserve -EAGAIN results.
These will be used by the pre-fault implementation which needs to retry
on -EAGAIN.

Also add an optional page_size output parameter to __user_mem_abort to
return the VMA page size, which will be needed for pre-faulting.

No functional changes are intended

Signed-off-by: Jack Thomson <jackabt@amazon.com>
---
arch/arm64/kvm/mmu.c | 36 +++++++++++++++++++++++++++++-------
1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index a36426ccd9b5..082e7d8ae655 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1521,9 +1521,9 @@ static void adjust_nested_fault_perms(struct kvm_s2_trans *nested,

#define KVM_PGTABLE_WALK_MEMABORT_FLAGS (KVM_PGTABLE_WALK_HANDLE_FAULT | KVM_PGTABLE_WALK_SHARED)

-static int gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
- struct kvm_s2_trans *nested,
- struct kvm_memory_slot *memslot, bool is_perm)
+static int __gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
+ struct kvm_s2_trans *nested,
+ struct kvm_memory_slot *memslot, bool is_perm)
{
bool write_fault, exec_fault, writable;
enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_MEMABORT_FLAGS;
@@ -1592,13 +1592,22 @@ static int gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (writable && !ret)
mark_page_dirty_in_slot(kvm, memslot, gfn);

+ return ret;
+}
+
+static int gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
+ struct kvm_s2_trans *nested,
+ struct kvm_memory_slot *memslot, bool is_perm)
+{
+ int ret = __gmem_abort(vcpu, fault_ipa, nested, memslot, is_perm);
return ret != -EAGAIN ? ret : 0;
}

-static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
- struct kvm_s2_trans *nested,
- struct kvm_memory_slot *memslot, unsigned long hva,
- bool fault_is_perm)
+static int __user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
+ struct kvm_s2_trans *nested,
+ struct kvm_memory_slot *memslot,
+ long *page_size, unsigned long hva,
+ bool fault_is_perm)
{
int ret = 0;
bool topup_memcache;
@@ -1871,10 +1880,23 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
kvm_release_faultin_page(kvm, page, !!ret, writable);
kvm_fault_unlock(kvm);

+ if (page_size)
+ *page_size = vma_pagesize;
+
/* Mark the page dirty only if the fault is handled successfully */
if (writable && !ret)
mark_page_dirty_in_slot(kvm, memslot, gfn);

+ return ret;
+}
+
+static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
+ struct kvm_s2_trans *nested,
+ struct kvm_memory_slot *memslot, unsigned long hva,
+ bool fault_is_perm)
+{
+ int ret = __user_mem_abort(vcpu, fault_ipa, nested, memslot, NULL,
+ hva, fault_is_perm);
return ret != -EAGAIN ? ret : 0;
}

--
2.43.0