[PATCH 2/3] kvmtool: arm64: Use the maximum supported IPA size when creating the VM

[Andre Przywara]

On Tue,  9 Mar 2021 16:39:08 +0000
Marc Zyngier <maz at kernel.org> wrote:

Hi,

> Instead of just asking the the default VM size, request the maximum
> IPA size to the kernel, and use this at VM creation time.
> 
> The IPA space is parametrized accordingly.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arm/aarch64/include/kvm/kvm-arch.h | 19 ++++++++++++++++---
>  arm/aarch64/kvm.c                  | 15 +++++++++++++++
>  2 files changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/arm/aarch64/include/kvm/kvm-arch.h b/arm/aarch64/include/kvm/kvm-arch.h
> index 55ef8ed..159567b 100644
> --- a/arm/aarch64/include/kvm/kvm-arch.h
> +++ b/arm/aarch64/include/kvm/kvm-arch.h
> @@ -3,10 +3,23 @@
>  
>  struct kvm;
>  unsigned long long kvm__arch_get_kern_offset(struct kvm *kvm, int fd);
> +int kvm__arch_get_ipa_limit(struct kvm *kvm);
>  
> -#define ARM_MAX_MEMORY(kvm)	((kvm)->cfg.arch.aarch32_guest	?	\
> -				ARM_LOMAP_MAX_MEMORY		:	\
> -				ARM_HIMAP_MAX_MEMORY)
> +#define ARM_MAX_MEMORY(kvm)	({					\
> +	u64 max_ram;							\
> +									\
> +	if ((kvm)->cfg.arch.aarch32_guest) {				\
> +		max_ram = ARM_LOMAP_MAX_MEMORY;				\
> +	} else {							\
> +		int ipabits = kvm__arch_get_ipa_limit(kvm);		\
> +		if (ipabits <= 0)					\
> +			max_ram = ARM_HIMAP_MAX_MEMORY;			\
> +		else							\
> +			max_ram = (1ULL << ipabits) - ARM_MEMORY_AREA;	\
> +	}								\
> +									\
> +	max_ram;							\
> +})
>  
>  #include "arm-common/kvm-arch.h"
>  
> diff --git a/arm/aarch64/kvm.c b/arm/aarch64/kvm.c
> index 49e1dd3..c4f81d0 100644
> --- a/arm/aarch64/kvm.c
> +++ b/arm/aarch64/kvm.c
> @@ -46,3 +46,18 @@ fail:
>  	return 0x80000;
>  }
>  
> +int kvm__arch_get_ipa_limit(struct kvm *kvm)
> +{
> +	int ret;
> +
> +	ret = ioctl(kvm->sys_fd, KVM_CHECK_EXTENSION, KVM_CAP_ARM_VM_IPA_SIZE);
> +	if (ret <= 0)
> +		ret = 0;
> +
> +	return ret;
> +}
> +
> +int kvm__get_vm_type(struct kvm *kvm)
> +{
> +	return kvm__arch_get_ipa_limit(kvm);

Shouldn't that be funnelled through KVM_VM_TYPE_ARM_IPA_SIZE()?
Granted, that doesn't really do anything, but if I understand the
api.rst directly, it's logically needed to convert the IPA size into a
VM type.

Other than that looks good.

Cheers,
Andre


> +}