On Tue, Jun 03, 2014 at 04:19:27PM -0700, Mario Smarduch wrote:
> This patch adds support for handling 2nd stage page faults during migration,
> it disables faulting in huge pages, and disolves huge pages to page tables.
s/disolves/dissolves/g
> In case migration is canceled huge pages will be used again.
>
> Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx>
> ---
> arch/arm/kvm/mmu.c | 36 ++++++++++++++++++++++++++++++++++--
> 1 file changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 1c546c9..aca4fbf 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -966,6 +966,8 @@ 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;
> + /* Get logging status, if dirty_bitmap is not NULL then logging is on */
> + bool logging_active = !!memslot->dirty_bitmap;
>
> write_fault = kvm_is_write_fault(kvm_vcpu_get_hsr(vcpu));
> if (fault_status == FSC_PERM && !write_fault) {
> @@ -1019,10 +1021,16 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> spin_lock(&kvm->mmu_lock);
> if (mmu_notifier_retry(kvm, mmu_seq))
> goto out_unlock;
> - if (!hugetlb && !force_pte)
> +
> + /* When logging don't spend cycles to check for huge pages */
drop the comment: either explain the entire clause (which would be too
long) or don't explain anything.
> + if (!hugetlb && !force_pte && !logging_active)
instead of having all this, can't you just change
if (is_vm_hugetlb_page(vma)) to
if (is_vm_hugetlb_page(vma) && !logging_active)
then you're also not mucking around with the gfn etc.
> hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
>
> - if (hugetlb) {
> + /*
> + * Force all not present/perm faults to PTE handling, address both
> + * PMD and PTE faults
> + */
I don't understand this comment? In which case does this apply?
> + if (hugetlb && !logging_active) {
> pmd_t new_pmd = pfn_pmd(pfn, PAGE_S2);
> new_pmd = pmd_mkhuge(new_pmd);
> if (writable) {
> @@ -1034,6 +1042,22 @@ 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) {
> + /*
> + * If pmd is mapping a huge page then clear it and let
> + * stage2_set_pte() create a pte table. At the sametime
> + * you write protect the pte (PAGE_S2 pgprot_t).
> + */
> + if (logging_active) {
> + pmd_t *pmd;
> + if (hugetlb) {
> + pfn += pte_index(fault_ipa);
> + gfn = fault_ipa >> PAGE_SHIFT;
> + 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);
> + }
now instead of all this, you just need to check for kvm_pmd_huge() in
stage2_set_pte() and if that's true, you clear it, and then then install
your new pte.
> kvm_set_s2pte_writable(&new_pte);
> kvm_set_pfn_dirty(pfn);
> }
> @@ -1041,6 +1065,14 @@ 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);
> }
>
> + /*
> + * Log the dirty page in dirty_bitmap[], call regardless if logging is
> + * disabled or enabled both cases handled safely.
> + * TODO: for larger page size mark mulitple dirty page bits for each
> + * 4k page.
> + */
> + if (writable)
> + mark_page_dirty(kvm, gfn);
what if you just faulted in a page on a read which wasn't present
before but it happens to belong to a writeable memslot, is that page
then dirty? hmmm.
>
> out_unlock:
> spin_unlock(&kvm->mmu_lock);
> --
> 1.7.9.5
>
Thanks,
-Christoffer
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