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    SubjectRe: [PATCH v19 024/130] KVM: TDX: Add placeholders for TDX VM/vcpu structure
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    On 26/02/2024 9:25 pm, Yamahata, Isaku wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > Add placeholders TDX VM/vcpu structure that overlays with VMX VM/vcpu
    > structures. Initialize VM structure size and vcpu size/align so that x86
    > KVM common code knows those size irrespective of VMX or TDX. Those
    > structures will be populated as guest creation logic develops.
    >
    > Add helper functions to check if the VM is guest TD and add conversion
    > functions between KVM VM/VCPU and TDX VM/VCPU.

    The changelog is essentially only saying "doing what" w/o "why".

    Please at least explain why you invented the 'struct kvm_tdx' and
    'struct vcpu_tdx', and why they are invented in this way.

    E.g., can we extend 'struct kvm_vmx' for TDX?

    struct kvm_tdx {
    struct kvm_vmx vmx;
    ...
    };

    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > ---
    > v19:
    > - correctly update ops.vm_size, vcpu_size and, vcpu_align by Xiaoyao
    >
    > v14 -> v15:
    > - use KVM_X86_TDX_VM
    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > ---
    > arch/x86/kvm/vmx/main.c | 14 ++++++++++++
    > arch/x86/kvm/vmx/tdx.c | 1 +
    > arch/x86/kvm/vmx/tdx.h | 50 +++++++++++++++++++++++++++++++++++++++++
    > 3 files changed, 65 insertions(+)
    > create mode 100644 arch/x86/kvm/vmx/tdx.h
    >
    > diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
    > index 18aef6e23aab..e11edbd19e7c 100644
    > --- a/arch/x86/kvm/vmx/main.c
    > +++ b/arch/x86/kvm/vmx/main.c
    > @@ -5,6 +5,7 @@
    > #include "vmx.h"
    > #include "nested.h"
    > #include "pmu.h"
    > +#include "tdx.h"
    >
    > static bool enable_tdx __ro_after_init;
    > module_param_named(tdx, enable_tdx, bool, 0444);
    > @@ -18,6 +19,9 @@ static __init int vt_hardware_setup(void)
    > return ret;
    >
    > enable_tdx = enable_tdx && !tdx_hardware_setup(&vt_x86_ops);
    > + if (enable_tdx)
    > + vt_x86_ops.vm_size = max_t(unsigned int, vt_x86_ops.vm_size,
    > + sizeof(struct kvm_tdx));
    >

    Now I see why you included 'struct kvm_x86_ops' as function parameter.

    Please move it to this patch.

    > return 0;
    > }
    > @@ -215,8 +219,18 @@ static int __init vt_init(void)
    > * Common KVM initialization _must_ come last, after this, /dev/kvm is
    > * exposed to userspace!
    > */
    > + /*
    > + * kvm_x86_ops is updated with vt_x86_ops. vt_x86_ops.vm_size must
    > + * be set before kvm_x86_vendor_init().
    > + */
    > vcpu_size = sizeof(struct vcpu_vmx);
    > vcpu_align = __alignof__(struct vcpu_vmx);
    > + if (enable_tdx) {
    > + vcpu_size = max_t(unsigned int, vcpu_size,
    > + sizeof(struct vcpu_tdx));
    > + vcpu_align = max_t(unsigned int, vcpu_align,
    > + __alignof__(struct vcpu_tdx));
    > + }

    Since you are updating vm_size in vt_hardware_setup(), I am wondering
    whether we can do similar thing for vcpu_size and vcpu_align.

    That is, we put them both to 'struct kvm_x86_ops', and you update them
    in vt_hardware_setup().

    kvm_init() can then just access them directly in this way both
    'vcpu_size' and 'vcpu_align' function parameters can be removed.


    > r = kvm_init(vcpu_size, vcpu_align, THIS_MODULE);
    > if (r)
    > goto err_kvm_init;

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