[PATCH v2 2/6] KVM: selftests: arm64: Introduce a variable default IPA size

[Andrew Jones]

On Mon, Dec 27, 2021 at 12:48:05PM +0000, Marc Zyngier wrote:
> Contrary to popular belief, there is no such thing as a default
> IPA size on arm64. Anything goes, and implementations are the
> usual Wild West.
> 
> The selftest infrastructure default to 40bit IPA, which obviously
> doesn't work for some systems out there.
> 
> Turn VM_MODE_DEFAULT from a constant into a variable, and let
> guest_modes_append_default() populate it, depending on what
> the HW can do. In order to preserve the current behaviour, we
> still pick 40bits IPA as the default if it is available, and
> the largest supported IPA space otherwise.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  .../testing/selftests/kvm/include/kvm_util.h  |  4 ++-
>  tools/testing/selftests/kvm/lib/guest_modes.c | 30 +++++++++++++++++--
>  2 files changed, 30 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 2d62edc49d67..7fa0a93d7526 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -53,7 +53,9 @@ enum vm_guest_mode {
>  
>  #if defined(__aarch64__)
>  
> -#define VM_MODE_DEFAULT			VM_MODE_P40V48_4K
> +extern enum vm_guest_mode vm_mode_default;
> +
> +#define VM_MODE_DEFAULT			vm_mode_default
>  #define MIN_PAGE_SHIFT			12U
>  #define ptes_per_page(page_size)	((page_size) / 8)
>  
> diff --git a/tools/testing/selftests/kvm/lib/guest_modes.c b/tools/testing/selftests/kvm/lib/guest_modes.c
> index c330f414ef96..5e3fdbd992fd 100644
> --- a/tools/testing/selftests/kvm/lib/guest_modes.c
> +++ b/tools/testing/selftests/kvm/lib/guest_modes.c
> @@ -4,22 +4,46 @@
>   */
>  #include "guest_modes.h"
>  
> +#ifdef __aarch64__
> +enum vm_guest_mode vm_mode_default;
> +#endif
> +
>  struct guest_mode guest_modes[NUM_VM_MODES];
>  
>  void guest_modes_append_default(void)
>  {
> +#ifndef __aarch64__
>  	guest_mode_append(VM_MODE_DEFAULT, true, true);
> -
> -#ifdef __aarch64__
> -	guest_mode_append(VM_MODE_P40V48_64K, true, true);
> +#else
>  	{
>  		unsigned int limit = kvm_check_cap(KVM_CAP_ARM_VM_IPA_SIZE);
> +		int i;
> +
> +		vm_mode_default = NUM_VM_MODES;
> +
>  		if (limit >= 52)
>  			guest_mode_append(VM_MODE_P52V48_64K, true, true);
>  		if (limit >= 48) {
>  			guest_mode_append(VM_MODE_P48V48_4K, true, true);
>  			guest_mode_append(VM_MODE_P48V48_64K, true, true);
>  		}
> +		if (limit >= 40) {
> +			guest_mode_append(VM_MODE_P40V48_4K, true, true);
> +			guest_mode_append(VM_MODE_P40V48_64K, true, true);
> +			vm_mode_default = VM_MODE_P40V48_4K;
> +		}
> +
> +		/*
> +		 * Pick the first supported IPA size if the default
> +		 * isn't available.
> +		 */
> +		for (i = 0; vm_mode_default == NUM_VM_MODES && i < NUM_VM_MODES; i++) {
> +			if (guest_modes[i].supported && guest_modes[i].enabled)
> +				vm_mode_default = i;

Since we don't have a 'break' here, this picks the last supported size
(of the guest_modes list), not the first, as the comment implies it should
do.

Thanks,
drew

> +		}
> +
> +		TEST_ASSERT(vm_mode_default != NUM_VM_MODES,
> +			    "No supported mode!");
>  	}
>  #endif
>  #ifdef __s390x__
> -- 
> 2.30.2
>