[PATCH] KVM: ppc64: Enable ring-based dirty memory tracking

[Kautuk Consul]

- Enable CONFIG_HAVE_KVM_DIRTY_RING_ACQ_REL as ppc64 is weakly
  ordered.
- Enable CONFIG_NEED_KVM_DIRTY_RING_WITH_BITMAP because the
  kvmppc_xive_native_set_attr is called in the context of an ioctl
  syscall and will call kvmppc_xive_native_eq_sync for setting the
  KVM_DEV_XIVE_EQ_SYNC attribute which will call mark_dirty_page()
  when there isn't a running vcpu. Implemented the
  kvm_arch_allow_write_without_running_vcpu to always return true
  to allow mark_page_dirty_in_slot to mark the page dirty in the
  memslot->dirty_bitmap in this case.
- Set KVM_DIRTY_LOG_PAGE_OFFSET for the ring buffer's physical page
  offset.
- Implement the kvm_arch_mmu_enable_log_dirty_pt_masked function required
  for the generic KVM code to call.
- Add a check to kvmppc_vcpu_run_hv for checking whether the dirty
  ring is soft full.
- Implement the kvm_arch_flush_remote_tlbs_memslot function to support
  the CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT config option.

On testing with live migration it was found that there is around
150-180 ms improvment in overall migration time with this patch.

Signed-off-by: Kautuk Consul <kconsul at linux.vnet.ibm.com>
---
 Documentation/virt/kvm/api.rst      |  2 +-
 arch/powerpc/include/uapi/asm/kvm.h |  2 ++
 arch/powerpc/kvm/Kconfig            |  2 ++
 arch/powerpc/kvm/book3s_64_mmu_hv.c | 42 +++++++++++++++++++++++++++++
 arch/powerpc/kvm/book3s_hv.c        |  3 +++
 include/linux/kvm_dirty_ring.h      |  5 ++++
 6 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index add067793b90..ce1ebc513bae 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8114,7 +8114,7 @@ regardless of what has actually been exposed through the CPUID leaf.
 8.29 KVM_CAP_DIRTY_LOG_RING/KVM_CAP_DIRTY_LOG_RING_ACQ_REL
 ----------------------------------------------------------
 
-:Architectures: x86, arm64
+:Architectures: x86, arm64, ppc64
 :Parameters: args[0] - size of the dirty log ring
 
 KVM is capable of tracking dirty memory using ring buffers that are
diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
index 9f18fa090f1f..f722309ed7fb 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -33,6 +33,8 @@
 /* Not always available, but if it is, this is the correct offset.  */
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
 
+#define KVM_DIRTY_LOG_PAGE_OFFSET 64
+
 struct kvm_regs {
 	__u64 pc;
 	__u64 cr;
diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index 902611954200..c93354ec3bd5 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -26,6 +26,8 @@ config KVM
 	select IRQ_BYPASS_MANAGER
 	select HAVE_KVM_IRQ_BYPASS
 	select INTERVAL_TREE
+	select HAVE_KVM_DIRTY_RING_ACQ_REL
+	select NEED_KVM_DIRTY_RING_WITH_BITMAP
 
 config KVM_BOOK3S_HANDLER
 	bool
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 7f765d5ad436..c92e8022e017 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -2147,3 +2147,45 @@ void kvmppc_mmu_book3s_hv_init(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.hflags |= BOOK3S_HFLAG_SLB;
 }
+
+/*
+ * kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
+ * dirty pages.
+ *
+ * It write protects selected pages to enable dirty logging for them.
+ */
+void kvm_arch_mmu_enable_log_dirty_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;
+
+	while (start < end) {
+		pte_t *ptep;
+		unsigned int shift;
+
+		ptep = find_kvm_secondary_pte(kvm, start, &shift);
+
+		*ptep = __pte(pte_val(*ptep) & ~(_PAGE_WRITE));
+
+		start += PAGE_SIZE;
+	}
+}
+
+#ifdef CONFIG_NEED_KVM_DIRTY_RING_WITH_BITMAP
+bool kvm_arch_allow_write_without_running_vcpu(struct kvm *kvm)
+{
+	return true;
+}
+#endif
+
+#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
+void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
+					const struct kvm_memory_slot *memslot)
+{
+	kvm_flush_remote_tlbs(kvm);
+}
+#endif
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 130bafdb1430..1d1264ea72c4 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4804,6 +4804,9 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu)
 		return -EINTR;
 	}
 
+	if (kvm_dirty_ring_check_request(vcpu))
+		return 0;
+
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	/*
 	 * Don't allow entry with a suspended transaction, because
diff --git a/include/linux/kvm_dirty_ring.h b/include/linux/kvm_dirty_ring.h
index 4862c98d80d3..a00301059da5 100644
--- a/include/linux/kvm_dirty_ring.h
+++ b/include/linux/kvm_dirty_ring.h
@@ -69,6 +69,11 @@ static inline void kvm_dirty_ring_free(struct kvm_dirty_ring *ring)
 {
 }
 
+static inline bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 #else /* CONFIG_HAVE_KVM_DIRTY_RING */
 
 int kvm_cpu_dirty_log_size(void);
-- 
2.39.2