Re: [PATCH] KVM: selftests: Speed up set_memory_region_test

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On 23/06/21 11:03, Zenghui Yu wrote:
On 2021/4/26 21:01, Vitaly Kuznetsov wrote:
After commit 4fc096a99e01 ("KVM: Raise the maximum number of user memslots")
set_memory_region_test may take too long, reports are that the default
timeout value we have (120s) may not be enough even on a physical host.

Speed things up a bit by throwing away vm_userspace_mem_region_add() usage from test_add_max_memory_regions(), we don't really need to do the majority
of the stuff it does for the sake of this test.

On my AMD EPYC 7401P, # time ./set_memory_region_test
pre-patch:
 Testing KVM_RUN with zero added memory regions
 Allowed number of memory slots: 32764
 Adding slots 0..32763, each memory region with 2048K size
 Testing MOVE of in-use region, 10 loops
 Testing DELETE of in-use region, 10 loops

 real    0m44.917s
 user    0m7.416s
 sys    0m34.601s

post-patch:
 Testing KVM_RUN with zero added memory regions
 Allowed number of memory slots: 32764
 Adding slots 0..32763, each memory region with 2048K size
 Testing MOVE of in-use region, 10 loops
 Testing DELETE of in-use region, 10 loops

 real    0m20.714s
 user    0m0.109s
 sys    0m18.359s

Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

I've seen the failure on my arm64 server, # ./set_memory_region_test

Allowed number of memory slots: 32767
Adding slots 0..32766, each memory region with 2048K size
==== Test Assertion Failure ====
   set_memory_region_test.c:391: ret == 0
   pid=42696 tid=42696 errno=22 - Invalid argument
     1    0x00000000004015a7: test_add_max_memory_regions at set_memory_region_test.c:389
      2     (inlined by) main at set_memory_region_test.c:426
      3    0x0000ffffb7c63bdf: ?? ??:0
      4    0x00000000004016db: _start at :?
   KVM_SET_USER_MEMORY_REGION IOCTL failed,
   rc: -1 errno: 22 slot: 2624

+    mem = mmap(NULL, MEM_REGION_SIZE * max_mem_slots + alignment,

The problem is that max_mem_slots is declared as uint32_t, the result
of (MEM_REGION_SIZE * max_mem_slots) is unexpectedly truncated to be
0xffe00000.

+           PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    TEST_ASSERT(mem != MAP_FAILED, "Failed to mmap() host");
+    mem_aligned = (void *)(((size_t) mem + alignment - 1) & ~(alignment - 1));
+
     for (slot = 0; slot < max_mem_slots; slot++) {
-        vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
-                        guest_addr, slot, mem_reg_npages,
-                        0);
-        guest_addr += MEM_REGION_SIZE;
+        ret = test_memory_region_add(vm, mem_aligned +
+                         ((uint64_t)slot * MEM_REGION_SIZE),

These unmapped VAs got caught by access_ok() checker in
__kvm_set_memory_region() as they happen to go beyond the task's
address space on arm64. Casting max_mem_slots to size_t in both
mmap() and munmap() fixes the issue for me.

Can you provide a patch for both?

Paolo




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