Re: [RFC PATCH 04/28] arm64: RME: Check for RME support at KVM init

Steven Price
2023-02-13T15:59:15Z

On 13/02/2023 15:48, Zhi Wang wrote:
> On Fri, 27 Jan 2023 11:29:08 +0000
> Steven Price <steven.price@arm.com> wrote:
>
>> Query the RMI version number and check if it is a compatible version. A
>> static key is also provided to signal that a supported RMM is available.
>>
>> Functions are provided to query if a VM or VCPU is a realm (or rec)
>> which currently will always return false.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>> arch/arm64/include/asm/kvm_emulate.h | 17 ++++++++++
>> arch/arm64/include/asm/kvm_host.h | 4 +++
>> arch/arm64/include/asm/kvm_rme.h | 22 +++++++++++++
>> arch/arm64/include/asm/virt.h | 1 +
>> arch/arm64/kvm/Makefile | 3 +-
>> arch/arm64/kvm/arm.c | 8 +++++
>> arch/arm64/kvm/rme.c | 49 ++++++++++++++++++++++++++++
>> 7 files changed, 103 insertions(+), 1 deletion(-)
>> create mode 100644 arch/arm64/include/asm/kvm_rme.h
>> create mode 100644 arch/arm64/kvm/rme.c
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 9bdba47f7e14..5a2b7229e83f 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -490,4 +490,21 @@ static inline bool vcpu_has_feature(struct kvm_vcpu *vcpu, int feature)
>> return test_bit(feature, vcpu->arch.features);
>> }
>>
>> +static inline bool kvm_is_realm(struct kvm *kvm)
>> +{
>> + if (static_branch_unlikely(&kvm_rme_is_available))
>> + return kvm->arch.is_realm;
>> + return false;
>> +}
>> +
>> +static inline enum realm_state kvm_realm_state(struct kvm *kvm)
>> +{
>> + return READ_ONCE(kvm->arch.realm.state);
>> +}
>> +
>> +static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu)
>> +{
>> + return false;
>> +}
>> +
>> #endif /* __ARM64_KVM_EMULATE_H__ */
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 35a159d131b5..04347c3a8c6b 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -26,6 +26,7 @@
>> #include <asm/fpsimd.h>
>> #include <asm/kvm.h>
>> #include <asm/kvm_asm.h>
>> +#include <asm/kvm_rme.h>
>>
>> #define __KVM_HAVE_ARCH_INTC_INITIALIZED
>>
>> @@ -240,6 +241,9 @@ struct kvm_arch {
>> * the associated pKVM instance in the hypervisor.
>> */
>> struct kvm_protected_vm pkvm;
>> +
>> + bool is_realm;
> ^
> It would be better to put more comments which really helps on the review.

Thanks for the feedback - I had thought "is realm" was fairly
self-documenting, but perhaps I've just spent too much time with this code.

> I was looking for the user of this memeber to see when it is set. It seems
> it is not in this patch. It would have been nice to have a quick answer from the
> comments.

The usage is in the kvm_is_realm() function which is used in several of
the later patches as a way to detect this kvm guest is a realm guest.

I think the main issue is that I've got the patches in the wrong other.
Patch 7 "arm64: kvm: Allow passing machine type in KVM creation" should
probably be before this one, then I could add the assignment of is_realm
into this patch (potentially splitting out the is_realm parts into
another patch).

Thanks,

Steve