[PATCH v2 2/2] accel: kvm: Add aligment assert for kvm_log_clear_one_slot

[Keqian Zhu]

The parameters start and size are transfered from QEMU memory
emulation layer. It can promise that they are TARGET_PAGE_SIZE
aligned. However, KVM needs they are qemu_real_page_size aligned.

Though no caller breaks this aligned requirement currently, we'd
better add an explicit assert to avoid future breaking.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
---
 accel/kvm/kvm-all.c | 7 +++++++
 1 file changed, 7 insertions(+)

---
v2
 - Address Andrew's commment (Use assert instead of return err).

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f6b16a8df8..73b195cc41 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -692,6 +692,10 @@ out:
 #define KVM_CLEAR_LOG_ALIGN  (qemu_real_host_page_size << KVM_CLEAR_LOG_SHIFT)
 #define KVM_CLEAR_LOG_MASK   (-KVM_CLEAR_LOG_ALIGN)
 
+/*
+ * As the granule of kvm dirty log is qemu_real_host_page_size,
+ * @start and @size are expected and restricted to align to it.
+ */
 static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, uint64_t start,
                                   uint64_t size)
 {
@@ -701,6 +705,9 @@ static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, 
uint64_t start,
     unsigned long *bmap_clear = NULL, psize = qemu_real_host_page_size;
     int ret;
 
+    /* Make sure start and size are qemu_real_host_page_size aligned */
+    assert(QEMU_IS_ALIGNED(start | size, psize));
+
     /*
      * We need to extend either the start or the size or both to
      * satisfy the KVM interface requirement.  Firstly, do the start
-- 
2.23.0