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SubjectRe: [PATCH] KVM: selftests: Speed up set_memory_region_test
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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@intel.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

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.

Thanks,
Zenghui

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