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    SubjectRe: [PATCH v8 003/103] KVM: Refactor CPU compatibility check on module initialization
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    On 2022/8/8 6:00, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > TDX module requires its initialization. It requires VMX to be enabled.
    > Although there are several options of when to initialize it, the choice is
    > the initialization time of the KVM kernel module. There is no usable
    > arch-specific hook for the TDX module to utilize during the KVM kernel module
    > initialization. The code doesn't enable/disable hardware (VMX in TDX case)
    > during the kernel module initialization. Add a hook for enabling hardware,
    > arch-specific initialization, and disabling hardware during KVM kernel
    > module initialization to make a room for TDX module initialization. The
    > current KVM enables hardware when the first VM is created and disables
    > hardware when the last VM is destroyed. When no VM is running, hardware is
    > disabled. To follow these semantics, the kernel module initialization needs
    > to disable hardware. Opportunistically refactor the code to enable/disable
    > hardware.
    >
    > Add hadware_enable_all() and hardware_disable_all() to kvm_init() and
    > introduce a new arch-specific callback function,
    > kvm_arch_post_hardware_enable_setup, for arch to do arch-specific
    > initialization that requires hardware_enable_all(). Opportunistically,
    > move kvm_arch_check_processor_compat() to to hardware_enabled_nolock().
    > TDX module initialization code will go into
    > kvm_arch_post_hardware_enable_setup().
    >
    > This patch reorders some function calls as below from (*) (**) (A) and (B)
    > to (A) (B) and (*). Here (A) and (B) depends on (*), but not (**). By
    > code inspection, only mips and VMX has the code of (*). No other
    No other or other?


    > arch has empty (*). So refactor mips and VMX and eliminate the
    > necessity hook for (*) instead of adding an unused hook.
    >
    > Before this patch:
    > - Arch module initialization
    > - kvm_init()
    > - kvm_arch_init()
    > - kvm_arch_check_processor_compat() on each CPUs
    > - post-arch-specific initialization -- (*): (A) and (B) depends on this
    > - post-arch-specific initialization -- (**): no dependency to (A) and (B)
    >
    > - When creating/deleting the first/last VM
    > - kvm_arch_hardware_enable() on each CPUs -- (A)
    > - kvm_arch_hardware_disable() on each CPUs -- (B)
    >
    > After this patch:
    > - Arch module initialization
    > - kvm_init()
    > - kvm_arch_init()
    > - arch-specific initialization -- (*)
    > - kvm_arch_check_processor_compat() on each CPUs
    > - kvm_arch_hardware_enable() on each CPUs -- (A)


    Maybe also put the new added kvm_arch_post_hardware_enable_setup here?
    After all, this is the purpose of this patch.


    > - kvm_arch_hardware_disable() on each CPUs -- (B)
    > - post-arch-specific initialization -- (**)
    >
    > - When creating/deleting the first/last VM (no logic change)
    > - kvm_arch_hardware_enable() on each CPUs -- (A)
    > - kvm_arch_hardware_disable() on each CPUs -- (B)
    >

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