linux-kernel - Re: [PATCH 6/6] KVM: selftests: x86: Add test for KVM_PRE_FAULT

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Date: Wed, 24 Apr 2024 09:59:43 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Cc: isaku.yamahata@...el.com, binbin.wu@...ux.intel.com, seanjc@...gle.com,
 rick.p.edgecombe@...el.com
Subject: Re: [PATCH 6/6] KVM: selftests: x86: Add test for
 KVM_PRE_FAULT_MEMORY

On 4/23/2024 11:18 PM, Xiaoyao Li wrote:
> On 4/19/2024 4:59 PM, Paolo Bonzini wrote:
> 
> ...
> 
>> +static void __test_pre_fault_memory(unsigned long vm_type, bool private)
>> +{
>> +    const struct vm_shape shape = {
>> +        .mode = VM_MODE_DEFAULT,
>> +        .type = vm_type,
>> +    };
>> +    struct kvm_vcpu *vcpu;
>> +    struct kvm_run *run;
>> +    struct kvm_vm *vm;
>> +    struct ucall uc;
>> +
>> +    uint64_t guest_test_phys_mem;
>> +    uint64_t guest_test_virt_mem;
>> +    uint64_t alignment, guest_page_size;
>> +
>> +    vm = vm_create_shape_with_one_vcpu(shape, &vcpu, guest_code);
>> +
>> +    alignment = guest_page_size = 
>> vm_guest_mode_params[VM_MODE_DEFAULT].page_size;
>> +    guest_test_phys_mem = (vm->max_gfn - TEST_NPAGES) * guest_page_size;
>> +#ifdef __s390x__
>> +    alignment = max(0x100000UL, guest_page_size);
>> +#else
>> +    alignment = SZ_2M;
>> +#endif
>> +    guest_test_phys_mem = align_down(guest_test_phys_mem, alignment);
>> +    guest_test_virt_mem = guest_test_phys_mem;
> 
> guest_test_virt_mem cannot be assigned as guest_test_phys_mem, which 
> leads to following virt_map() fails with

The root cause is that vm->pa_bits is 52 while vm->va_bits is 48. So 
vm->max_gfn is beyond the capability of va space

> ==== Test Assertion Failure ====
>    lib/x86_64/processor.c:197: sparsebit_is_set(vm->vpages_valid, (vaddr 
>  >> vm->page_shift))
>    pid=4773 tid=4773 errno=0 - Success
>       1    0x000000000040f55c: __virt_pg_map at processor.c:197
>       2    0x000000000040605e: virt_pg_map at kvm_util_base.h:1065
>       3     (inlined by) virt_map at kvm_util.c:1571
>       4    0x0000000000402b75: __test_pre_fault_memory at 
> pre_fault_memory_test.c:96
>       5    0x000000000040246e: test_pre_fault_memory at 
> pre_fault_memory_test.c:133 (discriminator 3)
>       6     (inlined by) main at pre_fault_memory_test.c:140 
> (discriminator 3)
>       7    0x00007fcb68429d8f: ?? ??:0
>       8    0x00007fcb68429e3f: ?? ??:0
>       9    0x00000000004024e4: _start at ??:?
>    Invalid virtual address, vaddr: 0xfffffffc00000
> 
>> +
>> +    vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
>> +                    guest_test_phys_mem, TEST_SLOT, TEST_NPAGES,
>> +                    private ? KVM_MEM_GUEST_MEMFD : 0);
>> +    virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, TEST_NPAGES);
> 
> 
> 
> 
>