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    SubjectRe: [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions
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    On 7/21/22 00:21, Sean Christopherson wrote:
    > On Wed, Jul 20, 2022, Gupta, Pankaj wrote:
    >>>>>>> +bool __weak kvm_arch_private_mem_supported(struct kvm *kvm)
    > Use kvm_arch_has_private_mem(), both because "has" makes it obvious this is checking
    > a flag of sorts, and to align with other helpers of this nature (and with
    > CONFIG_HAVE_KVM_PRIVATE_MEM).
    >
    > $ git grep kvm_arch | grep supported | wc -l
    > 0
    > $ git grep kvm_arch | grep has | wc -l
    > 26
    >
    >>>>>>> +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM
    >>>>>>> + case KVM_MEMORY_ENCRYPT_REG_REGION:
    >>>>>>> + case KVM_MEMORY_ENCRYPT_UNREG_REGION: {
    >>>>>>> + struct kvm_enc_region region;
    >>>>>>> +
    >>>>>>> + if (!kvm_arch_private_mem_supported(kvm))
    >>>>>>> + goto arch_vm_ioctl;
    >>>>>>> +
    >>>>>>> + r = -EFAULT;
    >>>>>>> + if (copy_from_user(&region, argp, sizeof(region)))
    >>>>>>> + goto out;
    >>>>>>> +
    >>>>>>> + r = kvm_vm_ioctl_set_encrypted_region(kvm, ioctl, &region);
    >>>>>> this is to store private region metadata not only the encrypted region?
    >>>>> Correct.
    >>>> Sorry for not being clear, was suggesting name change of this function from:
    >>>> "kvm_vm_ioctl_set_encrypted_region" to "kvm_vm_ioctl_set_private_region"
    >>> Though I don't have strong reason to change it, I'm fine with this and
    >> Yes, no strong reason, just thought "kvm_vm_ioctl_set_private_region" would
    >> depict the actual functionality :)
    >>
    >>> this name matches the above kvm_arch_private_mem_supported perfectly.
    >> BTW could not understand this, how "kvm_vm_ioctl_set_encrypted_region"
    >> matches "kvm_arch_private_mem_supported"?
    > Chao is saying that kvm_vm_ioctl_set_private_region() pairs nicely with
    > kvm_arch_private_mem_supported(), not that the "encrypted" variant pairs nicely.
    >
    > I also like using "private" instead of "encrypted", though we should probably
    > find a different verb than "set", because calling "set_private" when making the
    > region shared is confusing. I'm struggling to come up with a good alternative
    > though.
    >
    > kvm_vm_ioctl_set_memory_region() is already taken by KVM_SET_USER_MEMORY_REGION,
    > and that also means that anything with "memory_region" in the name is bound to be
    > confusing.
    >
    > Hmm, and if we move away from "encrypted", it probably makes sense to pass in
    > addr+size instead of a kvm_enc_region.
    >
    > Maybe this?
    >
    > static int kvm_vm_ioctl_set_or_clear_mem_private(struct kvm *kvm, gpa_t gpa,
    > gpa_t size, bool set_private)
    >
    > and then:
    >
    > #ifdef CONFIG_HAVE_KVM_PRIVATE_MEM
    > case KVM_MEMORY_ENCRYPT_REG_REGION:
    > case KVM_MEMORY_ENCRYPT_UNREG_REGION: {
    > bool set = ioctl == KVM_MEMORY_ENCRYPT_REG_REGION;
    > struct kvm_enc_region region;
    >
    > if (!kvm_arch_private_mem_supported(kvm))
    > goto arch_vm_ioctl;
    >
    > r = -EFAULT;
    > if (copy_from_user(&region, argp, sizeof(region)))
    > goto out;
    >
    > r = kvm_vm_ioctl_set_or_clear_mem_private(kvm, region.addr,
    > region.size, set);
    > break;
    > }
    > #endif
    >
    > I don't love it, so if someone has a better idea...
    >
    Maybe you could tag it with cgs for all the confidential guest support
    related stuff:
    e.g. kvm_vm_ioctl_set_cgs_mem()

    bool is_private = ioctl == KVM_MEMORY_ENCRYPT_REG_REGION;
    ...
    kvm_vm_ioctl_set_cgs_mem(, is_private)

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