On Mon, Jan 27, 2020 at 06:04:05PM +0100, Andrew Jones wrote:
> Guests and hosts don't have to have the same page size. This means
> calculations are necessary when selecting the number of guest pages
> to allocate in order to ensure the number is compatible with the
> host. Provide utilities to help with those calculations.
>
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/dirty_log_test.c | 3 +--
> .../testing/selftests/kvm/include/kvm_util.h | 3 +++
> tools/testing/selftests/kvm/lib/kvm_util.c | 26 +++++++++++++++++++
> 3 files changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
> index 5614222a6628..c2bc4e4c91ec 100644
> --- a/tools/testing/selftests/kvm/dirty_log_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_test.c
> @@ -295,8 +295,7 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations,
> guest_num_pages = (guest_num_pages + 0xff) & ~0xffUL;
> #endif
> host_page_size = getpagesize();
> - host_num_pages = (guest_num_pages * guest_page_size) / host_page_size +
> - !!((guest_num_pages * guest_page_size) % host_page_size);
> + host_num_pages = vm_num_host_pages(vm, guest_num_pages);
>
> if (!phys_offset) {
> guest_test_phys_mem = (vm_get_max_gfn(vm) -
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 29cccaf96baf..0d05ade3022c 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -158,6 +158,9 @@ unsigned int vm_get_page_size(struct kvm_vm *vm);
> unsigned int vm_get_page_shift(struct kvm_vm *vm);
> unsigned int vm_get_max_gfn(struct kvm_vm *vm);
>
> +unsigned int vm_num_host_pages(struct kvm_vm *vm, unsigned int num_guest_pages);
> +unsigned int vm_num_guest_pages(struct kvm_vm *vm, unsigned int num_host_pages);
> +
> struct kvm_userspace_memory_region *
> kvm_userspace_memory_region_find(struct kvm_vm *vm, uint64_t start,
> uint64_t end);
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 41cf45416060..5af9d7b1b7fc 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1667,3 +1667,29 @@ unsigned int vm_get_max_gfn(struct kvm_vm *vm)
> {
> return vm->max_gfn;
> }
> +
> +static unsigned int vm_calc_num_pages(unsigned int num_pages,
> + unsigned int page_shift,
> + unsigned int new_page_shift)
> +{
> + unsigned int n = 1 << (new_page_shift - page_shift);
> +
> + if (page_shift >= new_page_shift)
> + return num_pages * (1 << (page_shift - new_page_shift));
> +
> + return num_pages / n + !!(num_pages % n);
> +}
> +
> +unsigned int vm_num_host_pages(struct kvm_vm *vm, unsigned int num_guest_pages)
> +{
> + return vm_calc_num_pages(num_guest_pages,
> + vm_get_page_shift(vm),
> + __builtin_ffs(getpagesize()) - 1);
> +}
> +
> +unsigned int vm_num_guest_pages(struct kvm_vm *vm, unsigned int num_host_pages)
> +{
> + return vm_calc_num_pages(num_host_pages,
> + __builtin_ffs(getpagesize()) - 1,
> + vm_get_page_shift(vm));
> +}
> --
> 2.21.1
>
I'm going to send a v2 because there's another place in dirty_log_test.c
that I can apply this new utility. I'm also going to wrap the
'__builtin_ffs(getpagesize()) - 1' into a new getpageshift() macro.
Thanks,
drew
