linux-kernel - Re: [RFC PATCH v2 6/7] KVM: selftests: Adapt vm_userspace_mem_region

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Date:   Fri, 26 Feb 2021 13:48:44 +0800
From:   "wangyanan (Y)" <wangyanan55@...wei.com>
To:     Ben Gardon <bgardon@...gle.com>
CC:     kvm <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Jones <drjones@...hat.com>,
        Peter Xu <peterx@...hat.com>, Marc Zyngier <maz@...nel.org>,
        <wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>
Subject: Re: [RFC PATCH v2 6/7] KVM: selftests: Adapt
 vm_userspace_mem_region_add to new helpers


On 2021/2/26 7:44, Ben Gardon wrote:
> On Wed, Feb 24, 2021 at 10:03 PM Yanan Wang <wangyanan55@...wei.com> wrote:
>> With VM_MEM_SRC_ANONYMOUS_THP specified in vm_userspace_mem_region_add(),
>> we have to get the transparent hugepage size for HVA alignment. With the
>> new helpers, we can use get_backing_src_pagesz() to check whether THP is
>> configured and then get the exact configured hugepage size.
>>
>> As different architectures may have different THP page sizes configured,
>> this can get the accurate THP page sizes on any platform.
>>
>> Signed-off-by: Yanan Wang <wangyanan55@...wei.com>
>> ---
>>   tools/testing/selftests/kvm/lib/kvm_util.c | 27 +++++++---------------
>>   1 file changed, 8 insertions(+), 19 deletions(-)
>>
>> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
>> index b91c8e3a7ee1..0105fbfed036 100644
>> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
>> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
>> @@ -18,7 +18,6 @@
>>   #include <unistd.h>
>>   #include <linux/kernel.h>
>>
>> -#define KVM_UTIL_PGS_PER_HUGEPG 512
>>   #define KVM_UTIL_MIN_PFN       2
>>
>>   /* Aligns x up to the next multiple of size. Size must be a power of 2. */
>> @@ -686,7 +685,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
>>   {
>>          int ret;
>>          struct userspace_mem_region *region;
>> -       size_t huge_page_size = KVM_UTIL_PGS_PER_HUGEPG * vm->page_size;
>> +       size_t backing_src_pagesz = get_backing_src_pagesz(src_type);
>>          size_t alignment;
>>
>>          TEST_ASSERT(vm_adjust_num_guest_pages(vm->mode, npages) == npages,
>> @@ -748,7 +747,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
>>   #endif
>>
>>          if (src_type == VM_MEM_SRC_ANONYMOUS_THP)
>> -               alignment = max(huge_page_size, alignment);
>> +               alignment = max(backing_src_pagesz, alignment);
>>
>>          /* Add enough memory to align up if necessary */
>>          if (alignment > 1)
>> @@ -767,22 +766,12 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
>>          region->host_mem = align(region->mmap_start, alignment);
>>
>>          /* As needed perform madvise */
>> -       if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
>> -               struct stat statbuf;
>> -
>> -               ret = stat("/sys/kernel/mm/transparent_hugepage", &statbuf);
>> -               TEST_ASSERT(ret == 0 || (ret == -1 && errno == ENOENT),
>> -                           "stat /sys/kernel/mm/transparent_hugepage");
>> -
>> -               TEST_ASSERT(ret == 0 || src_type != VM_MEM_SRC_ANONYMOUS_THP,
>> -                           "VM_MEM_SRC_ANONYMOUS_THP requires THP to be configured in the host kernel");
>> -
>> -               if (ret == 0) {
>> -                       ret = madvise(region->host_mem, npages * vm->page_size,
>> -                                     src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
>> -                       TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %x",
>> -                                   region->host_mem, npages * vm->page_size, src_type);
>> -               }
>> +       if (src_type <= VM_MEM_SRC_ANONYMOUS_THP && thp_configured()) {
> This check relies on an unstated property of the backing src type
> enums where VM_MEM_SRC_ANONYMOUS and VM_MEM_SRC_ANONYMOUS_THP are
> declared first.
> It would probably be more readable for folks if the check was explicit:
> if ((src_type == VM_MEM_SRC_ANONYMOUS || src_type ==
> VM_MEM_SRC_ANONYMOUS_THP) && thp_configured()) {
>
Yes, this makes sense, I will fix it.

Thanks,

Yanan

>> +               ret = madvise(region->host_mem, npages * vm->page_size,
>> +                             src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
>> +               TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %s",
>> +                           region->host_mem, npages * vm->page_size,
>> +                           vm_mem_backing_src_alias(src_type)->name);
>>          }
>>
>>          region->unused_phy_pages = sparsebit_alloc();
>> --
>> 2.19.1
>>
> .