Re: [PATCH v4 08/10] ARM: KVM: Handle guest faults in KVM

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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.

+	} 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

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