Re: [RFC PATCH 07/28] arm64: kvm: Allow passing machine type in KVM creation

Steven Price
2023-03-01T11:55:41Z

On 13/02/2023 16:35, Zhi Wang wrote:
> On Fri, 27 Jan 2023 11:29:11 +0000
> Steven Price <steven.price@arm.com> wrote:
>
>> Previously machine type was used purely for specifying the physical
>> address size of the guest. Reserve the higher bits to specify an ARM
>> specific machine type and declare a new type 'KVM_VM_TYPE_ARM_REALM'
>> used to create a realm guest.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>> arch/arm64/kvm/arm.c | 13 +++++++++++++
>> arch/arm64/kvm/mmu.c | 3 ---
>> arch/arm64/kvm/reset.c | 3 ---
>> include/uapi/linux/kvm.h | 19 +++++++++++++++----
>> 4 files changed, 28 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 50f54a63732a..badd775547b8 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -147,6 +147,19 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>> {
>> int ret;
>>
>> + if (type & ~(KVM_VM_TYPE_ARM_MASK | KVM_VM_TYPE_ARM_IPA_SIZE_MASK))
>> + return -EINVAL;
>> +
>> + switch (type & KVM_VM_TYPE_ARM_MASK) {
>> + case KVM_VM_TYPE_ARM_NORMAL:
>> + break;
>> + case KVM_VM_TYPE_ARM_REALM:
>> + kvm->arch.is_realm = true;
>
> It is better to let this call fail when !kvm_rme_is_available? It is
> strange to be able to create a VM with REALM type in a system doesn't
> support RME.

Good point - I'll add a check here.

Thanks,

Steve

>> + break;
>> + default:
>> + return -EINVAL;
>> + }
>> +
>> ret = kvm_share_hyp(kvm, kvm + 1);
>> if (ret)
>> return ret;
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index d0f707767d05..22c00274884a 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -709,9 +709,6 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
>> u64 mmfr0, mmfr1;
>> u32 phys_shift;
>>
>> - if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
>> - return -EINVAL;
>> -
>> phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
>> if (is_protected_kvm_enabled()) {
>> phys_shift = kvm_ipa_limit;
>> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
>> index c165df174737..9e71d69e051f 100644
>> --- a/arch/arm64/kvm/reset.c
>> +++ b/arch/arm64/kvm/reset.c
>> @@ -405,9 +405,6 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type)
>> if (kvm_is_realm(kvm))
>> ipa_limit = kvm_realm_ipa_limit();
>>
>> - if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
>> - return -EINVAL;
>> -
>> phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
>> if (phys_shift) {
>> if (phys_shift > ipa_limit ||
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index fec1909e8b73..bcfc4d58dc19 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -898,14 +898,25 @@ struct kvm_ppc_resize_hpt {
>> #define KVM_S390_SIE_PAGE_OFFSET 1
>>
>> /*
>> - * On arm64, machine type can be used to request the physical
>> - * address size for the VM. Bits[7-0] are reserved for the guest
>> - * PA size shift (i.e, log2(PA_Size)). For backward compatibility,
>> - * value 0 implies the default IPA size, 40bits.
>> + * On arm64, machine type can be used to request both the machine type and
>> + * the physical address size for the VM.
>> + *
>> + * Bits[11-8] are reserved for the ARM specific machine type.
>> + *
>> + * Bits[7-0] are reserved for the guest PA size shift (i.e, log2(PA_Size)).
>> + * For backward compatibility, value 0 implies the default IPA size, 40bits.
>> */
>> +#define KVM_VM_TYPE_ARM_SHIFT 8
>> +#define KVM_VM_TYPE_ARM_MASK (0xfULL << KVM_VM_TYPE_ARM_SHIFT)
>> +#define KVM_VM_TYPE_ARM(_type) \
>> + (((_type) << KVM_VM_TYPE_ARM_SHIFT) & KVM_VM_TYPE_ARM_MASK)
>> +#define KVM_VM_TYPE_ARM_NORMAL KVM_VM_TYPE_ARM(0)
>> +#define KVM_VM_TYPE_ARM_REALM KVM_VM_TYPE_ARM(1)
>> +
>> #define KVM_VM_TYPE_ARM_IPA_SIZE_MASK 0xffULL
>> #define KVM_VM_TYPE_ARM_IPA_SIZE(x) \
>> ((x) & KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
>> +
>> /*
>> * ioctls for /dev/kvm fds:
>> */
>