[RESEND PATCH v14 7/7] KVM: arm: page logging 2nd stage fault handling
Mario Smarduch
m.smarduch at samsung.com
Mon Nov 24 17:09:54 PST 2014
On 11/24/2014 12:02 PM, Mario Smarduch wrote:
> On 11/22/2014 11:53 AM, Christoffer Dall wrote:
>> On Fri, Nov 14, 2014 at 01:54:44PM -0800, Mario Smarduch wrote:
>>> This patch adds support for handling 2nd stage page faults during migration,
>>> it disables faulting in huge pages, and dissolves huge pages to page tables.
>>> In case migration is canceled huge pages are used again.
>>>
>>> Resending to addresse Marc's comments to simplify stage2_set_pte() handling
>>> of logging, and mapping device memory - flags.
>>>
>>> Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
>>> Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>
>>> Signed-off-by: Mario Smarduch <m.smarduch at samsung.com>
>>> ---
>>> arch/arm/kvm/mmu.c | 61 +++++++++++++++++++++++++++++++++++++++++++++-------
>>> 1 file changed, 53 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>> index 8137455..d29de77 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>>> @@ -47,6 +47,18 @@ static phys_addr_t hyp_idmap_vector;
>>> #define kvm_pmd_huge(_x) (pmd_huge(_x) || pmd_trans_huge(_x))
>>> #define kvm_pud_huge(_x) pud_huge(_x)
>>>
>>> +#define KVM_S2PTE_FLAG_IS_IOMAP (1UL << 0)
>>> +#define KVM_S2PTE_FLAG_LOGGING_ACTIVE (1UL << 1)
>>> +
>>> +static bool kvm_get_logging_state(struct kvm_memory_slot *memslot)
>>> +{
>>> +#ifdef CONFIG_ARM
>>> + return !!memslot->dirty_bitmap;
>>> +#else
>>> + return false;
>>> +#endif
>>> +}
>>> +
>>> static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
>>> {
>>> /*
>>> @@ -626,10 +638,13 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
>>> }
>>>
>>> static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
>>> - phys_addr_t addr, const pte_t *new_pte, bool iomap)
>>> + phys_addr_t addr, const pte_t *new_pte,
>>> + unsigned long flags)
>>> {
>>> pmd_t *pmd;
>>> pte_t *pte, old_pte;
>>> + unsigned long iomap = flags & KVM_S2PTE_FLAG_IS_IOMAP;
>>> + unsigned long logging_active = flags & KVM_S2PTE_FLAG_LOGGING_ACTIVE;
>>>
>>> /* Create stage-2 page table mapping - Level 1 */
>>> pmd = stage2_get_pmd(kvm, cache, addr);
>>> @@ -641,6 +656,18 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
>>> return 0;
>>> }
>>>
>>> + /*
>>> + * While dirty memory logging, clear PMD entry for huge page and split
>>> + * into smaller pages, to track dirty memory at page granularity.
>>> + */
>>> + if (logging_active && kvm_pmd_huge(*pmd)) {
>>> + phys_addr_t ipa = pmd_pfn(*pmd) << PAGE_SHIFT;
>>
>> just noticed this: this is not an IPA is it? pmd_pfn should give us the
>> host pfn. I think you need to manipulate @addr instead.
>>
>> Did I manage to confuse myself?
> No you're right, a *bad mistake* on my part I broke it between v8 and
> v9. Not sure how it happened absent minded cut and paste?
>
> Also when the pmd is cleared, should that be flushed
> to level where the pmd is visible to page table walks?
> Or am I confusing something here?
Hi Christoffer,
disregard question, sorry for the unnecessary traffic.
>
> Thanks.
>>
>> (Yeah, I know I said I reviewed this one already)
>>
>>> +
>>> + pmd_clear(pmd);
>>> + kvm_tlb_flush_vmid_ipa(kvm, ipa);
>>> + put_page(virt_to_page(pmd));
>>> + }
>>> +
>>> /* Create stage-2 page mappings - Level 2 */
>>> if (pmd_none(*pmd)) {
>>> if (!cache)
>>> @@ -693,7 +720,8 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>>> if (ret)
>>> goto out;
>>> spin_lock(&kvm->mmu_lock);
>>> - ret = stage2_set_pte(kvm, &cache, addr, &pte, true);
>>> + ret = stage2_set_pte(kvm, &cache, addr, &pte,
>>> + KVM_S2PTE_FLAG_IS_IOMAP);
>>> spin_unlock(&kvm->mmu_lock);
>>> if (ret)
>>> goto out;
>>> @@ -908,6 +936,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>> struct vm_area_struct *vma;
>>> pfn_t pfn;
>>> pgprot_t mem_type = PAGE_S2;
>>> + unsigned long logging_active = 0;
>>> +
>>> + if (kvm_get_logging_state(memslot))
>>> + logging_active = KVM_S2PTE_FLAG_LOGGING_ACTIVE;
>>>
>>> write_fault = kvm_is_write_fault(kvm_vcpu_get_hsr(vcpu));
>>> if (fault_status == FSC_PERM && !write_fault) {
>>> @@ -918,7 +950,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>> /* Let's check if we will get back a huge page backed by hugetlbfs */
>>> down_read(¤t->mm->mmap_sem);
>>> vma = find_vma_intersection(current->mm, hva, hva + 1);
>>> - if (is_vm_hugetlb_page(vma)) {
>>> + if (is_vm_hugetlb_page(vma) && !logging_active) {
>>> hugetlb = true;
>>> gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
>>> } else {
>>> @@ -964,7 +996,7 @@ 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)
>>> + if (!hugetlb && !force_pte && !logging_active)
>>> hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
>>>
>>> if (hugetlb) {
>>> @@ -978,16 +1010,21 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>> ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
>>> } else {
>>> pte_t new_pte = pfn_pte(pfn, mem_type);
>>> + unsigned long flags = logging_active;
>>> +
>>> + if (mem_type == PAGE_S2_DEVICE)
>>> + flags |= KVM_S2PTE_FLAG_IS_IOMAP;
>>> +
>>> if (writable) {
>>> kvm_set_s2pte_writable(&new_pte);
>>> kvm_set_pfn_dirty(pfn);
>>> }
>>> coherent_cache_guest_page(vcpu, hva, PAGE_SIZE);
>>> - ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte,
>>> - mem_type == PAGE_S2_DEVICE);
>>> + ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, flags);
>>> }
>>>
>>> -
>>> + if (write_fault)
>>> + mark_page_dirty(kvm, gfn);
>>> out_unlock:
>>> spin_unlock(&kvm->mmu_lock);
>>> kvm_release_pfn_clean(pfn);
>>> @@ -1137,7 +1174,15 @@ static void kvm_set_spte_handler(struct kvm *kvm, gpa_t gpa, void *data)
>>> {
>>> pte_t *pte = (pte_t *)data;
>>>
>>> - stage2_set_pte(kvm, NULL, gpa, pte, false);
>>> + /*
>>> + * We can always call stage2_set_pte with logging_active == false,
>>
>> this should now say without the KVM_S2PTE_FLAG_LOGGING_ACTIVE flag.
>>
>>> + * because MMU notifiers will have unmapped a huge PMD before calling
>>> + * ->change_pte() (which in turn calls kvm_set_spte_hva()) and therefore
>>> + * stage2_set_pte() never needs to clear out a huge PMD through this
>>> + * calling path.
>>> + */
>>> +
>>> + stage2_set_pte(kvm, NULL, gpa, pte, 0);
>>> }
>>>
>>>
>>> --
>>> 1.7.9.5
>>>
>
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