Additional logic to handle second stage page faults during migration. Primarily
page faults are prevented from creating huge pages.
Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx>
---
arch/arm/kvm/mmu.c | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 47bec1c..ebec33c 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -839,6 +839,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
struct vm_area_struct *vma;
pfn_t pfn;
+ bool migration_active;
write_fault = kvm_is_write_fault(kvm_vcpu_get_hsr(vcpu));
if (fault_status == FSC_PERM && !write_fault) {
@@ -890,12 +891,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
return -EFAULT;
spin_lock(&kvm->mmu_lock);
+ /* place inside lock to prevent race condition when whole VM is being
+ * write proteced initially, prevent pmd update if it's split up.
+ */
+ migration_active = vcpu->kvm->arch.migration_in_progress;
+
if (mmu_notifier_retry(kvm, mmu_seq))
goto out_unlock;
- if (!hugetlb && !force_pte)
+
+ /* During migration don't rebuild huge pages */
+ if (!hugetlb && !force_pte && !migration_active)
hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
- if (hugetlb) {
+ /* Steer away from installing PMDs if migrating, migration failed,
+ * or this an initial page fault. Migrating huge pages is too slow.
+ */
+ if (!migration_active && hugetlb) {
pmd_t new_pmd = pfn_pmd(pfn, PAGE_S2);
new_pmd = pmd_mkhuge(new_pmd);
if (writable) {
@@ -907,6 +918,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
} else {
pte_t new_pte = pfn_pte(pfn, PAGE_S2);
if (writable) {
+ /* First convert huge page pfn to normal 4k page pfn,
+ * while migration is in progress.
+ * Second in migration mode and rare case where
+ * splitting of huge pages fails check if pmd is
+ * mapping a huge page if it is then clear it so
+ * stage2_set_pte() can map in a small page.
+ */
+ if (migration_active && hugetlb) {
+ pmd_t *pmd;
+ pfn += (fault_ipa >> PAGE_SHIFT) &
+ (PTRS_PER_PMD-1);
+ new_pte = pfn_pte(pfn, PAGE_S2);
+ pmd = stage2_get_pmd(kvm, NULL, fault_ipa);
+ if (pmd && kvm_pmd_huge(*pmd))
+ clear_pmd_entry(kvm, pmd, fault_ipa);
+ }
kvm_set_s2pte_writable(&new_pte);
kvm_set_pfn_dirty(pfn);
}
@@ -914,6 +941,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, false);
}
+ if (writable)
+ mark_page_dirty(kvm, gfn);
out_unlock:
spin_unlock(&kvm->mmu_lock);
--
1.7.9.5
--
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