KVM: arm: dirty logging write protect support

Add support to track dirty pages between user space KVM_GET_DIRTY_LOG ioctl
calls. We call kvm_get_dirty_log_protect() function to do most of the work.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>

diff --git a/arch/arm/kvm/Kconfig b/arch/arm/kvm/Kconfig
index f27f3360e52b3d8c9d70828e716e1468df96b233..a8d1ace3ea51fa502d8b2060e35168c06bb0ffb7 100644 (file)
--- a/arch/arm/kvm/Kconfig
+++ b/arch/arm/kvm/Kconfig
@@ -24,6 +24,7 @@ config KVM
        select HAVE_KVM_ARCH_TLB_FLUSH_ALL
        select KVM_MMIO
        select KVM_ARM_HOST
+       select KVM_GENERIC_DIRTYLOG_READ_PROTECT
        depends on ARM_VIRT_EXT && ARM_LPAE
        ---help---
          Support hosting virtualized guest machines. You will also

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 2d6d91001062f975981dd9beed2b43815f73c238..1434410e7f46b1c560f2f18a3aaee72f6e48a79b 100644 (file)
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -787,9 +787,43 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
        }
 }
 
+/**
+ * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
+ * @kvm: kvm instance
+ * @log: slot id and address to which we copy the log
+ *
+ * Steps 1-4 below provide general overview of dirty page logging. See
+ * kvm_get_dirty_log_protect() function description for additional details.
+ *
+ * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
+ * always flush the TLB (step 4) even if previous step failed  and the dirty
+ * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
+ * does not preclude user space subsequent dirty log read. Flushing TLB ensures
+ * writes will be marked dirty for next log read.
+ *
+ *   1. Take a snapshot of the bit and clear it if needed.
+ *   2. Write protect the corresponding page.
+ *   3. Copy the snapshot to the userspace.
+ *   4. Flush TLB's if needed.
+ */
 int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
 {
+#ifdef CONFIG_ARM
+       bool is_dirty = false;
+       int r;
+
+       mutex_lock(&kvm->slots_lock);
+
+       r = kvm_get_dirty_log_protect(kvm, log, &is_dirty);
+
+       if (is_dirty)
+               kvm_flush_remote_tlbs(kvm);
+
+       mutex_unlock(&kvm->slots_lock);
+       return r;
+#else /* arm64 */
        return -EINVAL;
+#endif
 }
 
 static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index c9e5f384832ed0316ed5781c7cf8e249d6d8c122..565e903f6f78729c1ac13300f674c3729c9d8524 100644 (file)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1029,6 +1029,28 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot)
        spin_unlock(&kvm->mmu_lock);
        kvm_flush_remote_tlbs(kvm);
 }
+
+/**
+ * kvm_arch_mmu_write_protect_pt_masked() - write protect dirty pages
+ * @kvm:       The KVM pointer
+ * @slot:      The memory slot associated with mask
+ * @gfn_offset:        The gfn offset in memory slot
+ * @mask:      The mask of dirty pages at offset 'gfn_offset' in this memory
+ *             slot to be write protected
+ *
+ * Walks bits set in mask write protects the associated pte's. Caller must
+ * acquire kvm_mmu_lock.
+ */
+void kvm_arch_mmu_write_protect_pt_masked(struct kvm *kvm,
+               struct kvm_memory_slot *slot,
+               gfn_t gfn_offset, unsigned long mask)
+{
+       phys_addr_t base_gfn = slot->base_gfn + gfn_offset;
+       phys_addr_t start = (base_gfn +  __ffs(mask)) << PAGE_SHIFT;
+       phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
+
+       stage2_wp_range(kvm, start, end);
+}
 #endif
 
 static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,