Re: [PATCH/RFC] KVM: selftests: introduce P44V64 for z196 and EC12

[Thomas Huth <thuth@redhat.com>]

On 01/07/2021 17.38, Christian Borntraeger wrote:
> Older machines likes z196 and zEC12 do only support 44 bits of physical
> addresses. Make this the default and check via IBC if we are on a later
> machine. We then add P47V64 as an additional model.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Fixes: 1bc603af73dd ("KVM: selftests: introduce P47V64 for s390x")
> ---
>   tools/testing/selftests/kvm/include/kvm_util.h |  3 ++-
>   tools/testing/selftests/kvm/lib/guest_modes.c  | 16 ++++++++++++++++
>   tools/testing/selftests/kvm/lib/kvm_util.c     |  5 +++++
>   3 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 35739567189e..74d73532fce9 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -44,6 +44,7 @@ enum vm_guest_mode {
>   	VM_MODE_P40V48_64K,
>   	VM_MODE_PXXV48_4K,	/* For 48bits VA but ANY bits PA */
>   	VM_MODE_P47V64_4K,
> +	VM_MODE_P44V64_4K,
>   	NUM_VM_MODES,
>   };
>   
> @@ -61,7 +62,7 @@ enum vm_guest_mode {
>   
>   #elif defined(__s390x__)
>   
> -#define VM_MODE_DEFAULT			VM_MODE_P47V64_4K
> +#define VM_MODE_DEFAULT			VM_MODE_P44V64_4K
>   #define MIN_PAGE_SHIFT			12U
>   #define ptes_per_page(page_size)	((page_size) / 16)
>   
> diff --git a/tools/testing/selftests/kvm/lib/guest_modes.c b/tools/testing/selftests/kvm/lib/guest_modes.c
> index 25bff307c71f..c330f414ef96 100644
> --- a/tools/testing/selftests/kvm/lib/guest_modes.c
> +++ b/tools/testing/selftests/kvm/lib/guest_modes.c
> @@ -22,6 +22,22 @@ void guest_modes_append_default(void)
>   		}
>   	}
>   #endif
> +#ifdef __s390x__
> +	{
> +		int kvm_fd, vm_fd;
> +		struct kvm_s390_vm_cpu_processor info;
> +
> +		kvm_fd = open_kvm_dev_path_or_exit();
> +		vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
> +		kvm_device_access(vm_fd, KVM_S390_VM_CPU_MODEL,
> +				  KVM_S390_VM_CPU_PROCESSOR, &info, false);
> +		close(vm_fd);
> +		close(kvm_fd);
> +		/* Starting with z13 we have 47bits of physical address */
> +		if (info.ibc >= 0x30)
> +			guest_mode_append(VM_MODE_P47V64_4K, true, true);

Wouldn't it make more sense to check the processor number in /proc/cpuinfo? 
... well, I guess both ways of checking have their advantages and 
disadvantages, so anyway:

Reviewed-by: Thomas Huth <thuth@redhat.com>