On Aug 9, 2011, at 1:24 PM, Avi Kivity wrote:
> On 08/06/2011 01:39 PM, Christoffer Dall wrote:
>> Handles the guest faults in KVM by mapping in corresponding user pages
>> in the 2nd stage page tables.
>>
>> Introduces new ARM-specific kernel memory types, PAGE_KVM_GUEST and
>> pgprot_guest variables used to map 2nd stage memory for KVM guests.
>>
>>
>>
>> +static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> + gfn_t gfn, struct kvm_memory_slot *memslot)
>> +{
>> + pfn_t pfn;
>> + pgd_t *pgd;
>> + pud_t *pud;
>> + pmd_t *pmd;
>> + pte_t *pte, new_pte;
>> +
>> + pfn = gfn_to_pfn(vcpu->kvm, gfn);
>> +
>> + if (is_error_pfn(pfn)) {
>> + kvm_err(-EFAULT, "Guest gfn %u (0x%08lx) does not have "
>> + "corresponding host mapping",
>> + gfn, gfn<< PAGE_SHIFT);
>> + return -EFAULT;
>> + }
>> +
>> + /* Create 2nd stage page table mapping - Level 1 */
>> + pgd = vcpu->kvm->arch.pgd + pgd_index(fault_ipa);
>> + pud = pud_offset(pgd, fault_ipa);
>> + if (pud_none(*pud)) {
>> + pmd = pmd_alloc_one(NULL, fault_ipa);
>> + if (!pmd) {
>> + kvm_err(-ENOMEM, "Cannot allocate 2nd stage pmd");
>> + return -ENOMEM;
>> + }
>> + pud_populate(NULL, pud, pmd);
>> + pmd += pmd_index(fault_ipa);
>
> Don't we need locking here? Another vcpu may have executed pud_populate concurrently.
Absolutely, but there is no SMP support yet and only a single VCPU is supported. Again, focus area in next patch series and thanks for the pinpoint.
>
>> + } else
>> + pmd = pmd_offset(pud, fault_ipa);
>> +
>> + /* Create 2nd stage page table mapping - Level 2 */
>> + if (pmd_none(*pmd)) {
>> + pte = pte_alloc_one_kernel(NULL, fault_ipa);
>> + if (!pte) {
>> + kvm_err(-ENOMEM, "Cannot allocate 2nd stage pte");
>> + return -ENOMEM;
>> + }
>> + pmd_populate_kernel(NULL, pmd, pte);
>> + pte += pte_index(fault_ipa);
>> + } else
>> + pte = pte_offset_kernel(pmd, fault_ipa);
>> +
>> + /* Create 2nd stage page table mapping - Level 3 */
>> + new_pte = pfn_pte(pfn, PAGE_KVM_GUEST);
>> + set_pte_ext(pte, new_pte, 0);
>> +
>> + return 0;
>> +}
>> +
>> +#define HSR_ABT_FS (0x3f)
>>
>
> --
> error compiling committee.c: too many arguments to function
>
