Re: [RFC PATCH 1/2] KVM: selftests: Add a macro to get string of vm_mem_backing_src_type

Sean Christopherson
2021-02-08T17:53:50Z

On Mon, Feb 08, 2021, Yanan Wang wrote:
> Add a macro to get string of the backing source memory type, so that
> application can add choices for source types in the help() function,
> and users can specify which type to use for testing.
>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
> tools/testing/selftests/kvm/include/kvm_util.h | 3 +++
> tools/testing/selftests/kvm/lib/kvm_util.c | 8 ++++++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 5cbb861525ed..f5fc29dc9ee6 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -69,7 +69,9 @@ enum vm_guest_mode {
> #define PTES_PER_MIN_PAGE ptes_per_page(MIN_PAGE_SIZE)
>
> #define vm_guest_mode_string(m) vm_guest_mode_string[m]
> +#define vm_mem_backing_src_type_string(s) vm_mem_backing_src_type_string[s]

Oof, I see this is just following vm_guest_mode_string. IMO, defining the
string to look like a function is unnecessary and rather mean.

> extern const char * const vm_guest_mode_string[];
> +extern const char * const vm_mem_backing_src_type_string[];
>
> struct vm_guest_mode_params {
> unsigned int pa_bits;
> @@ -83,6 +85,7 @@ enum vm_mem_backing_src_type {
> VM_MEM_SRC_ANONYMOUS,
> VM_MEM_SRC_ANONYMOUS_THP,
> VM_MEM_SRC_ANONYMOUS_HUGETLB,
> + NUM_VM_BACKING_SRC_TYPES,
> };
>
> int kvm_check_cap(long cap);
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index fa5a90e6c6f0..a9b651c7f866 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -165,6 +165,14 @@ const struct vm_guest_mode_params vm_guest_mode_params[] = {
> _Static_assert(sizeof(vm_guest_mode_params)/sizeof(struct vm_guest_mode_params) == NUM_VM_MODES,
> "Missing new mode params?");
>
> +const char * const vm_mem_backing_src_type_string[] = {

A shorter name would be nice, though I don't have a good suggestion.

> + "VM_MEM_SRC_ANONYMOUS ",
> + "VM_MEM_SRC_ANONYMOUS_THP ",
> + "VM_MEM_SRC_ANONYMOUS_HUGETLB",

It'd be more robust to explicitly assign indices, that way tweaks to
vm_mem_backing_src_type won't cause silent breakage. Ditto for the existing
vm_guest_mode_string.

E.g. I think something like this would work (completely untested)

const char *vm_guest_mode_string(int i)
{
static const char *const strings[] = {
[VM_MODE_P52V48_4K] = "PA-bits:52, VA-bits:48, 4K pages",
[VM_MODE_P52V48_64K] = "PA-bits:52, VA-bits:48, 64K pages",
[VM_MODE_P48V48_4K] = "PA-bits:48, VA-bits:48, 4K pages",
[VM_MODE_P48V48_64K] = "PA-bits:48, VA-bits:48, 64K pages",
[VM_MODE_P40V48_4K] = "PA-bits:40, VA-bits:48, 4K pages",
[VM_MODE_P40V48_64K] = "PA-bits:40, VA-bits:48, 64K pages",
[VM_MODE_PXXV48_4K] = "PA-bits:ANY, VA-bits:48, 4K pages",
};

_Static_assert(sizeof(strings)/sizeof(char *) == NUM_VM_MODES,
"Missing new mode strings?");

TEST_ASSERT(i < NUM_VM_MODES);

return strings[i];
}

> +};
> +_Static_assert(sizeof(vm_mem_backing_src_type_string)/sizeof(char *) == NUM_VM_BACKING_SRC_TYPES,
> + "Missing new source type strings?");
> +
> /*
> * VM Create
> *
> --
> 2.23.0
>