linux-kernel - Re: [PATCH v14 004/113] KVM: TDX: Initialize the TDX module when loading the KVM intel kernel module

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Date:   Mon, 12 Jun 2023 23:55:14 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
CC:     "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chen, Bo2" <chen.bo@...el.com>, "Shahar, Sagi" <sagis@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "zhi.wang.linux@...il.com" <zhi.wang.linux@...il.com>
Subject: Re: [PATCH v14 004/113] KVM: TDX: Initialize the TDX module when
 loading the KVM intel kernel module

On Wed, 2023-06-07 at 11:06 -0700, Isaku Yamahata wrote:
> Thanks for pointing it out. The following is the fix.
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 8a1d0755d275..b0d3f646afb1 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -4499,26 +4499,39 @@ u64 tdx_non_arch_field_switch(u64 field)
>  	}
>  }
>  
> -static void __init vmx_tdx_on(void *info)
> +struct vmx_tdx_enabled {
> +	cpumask_var_t vmx_enabled;
> +	atomic_t *err;
> +};
> +

Sorry for late reply.

I think you just need to mimic hardware_enable_all() -- using a per-cpu
variable.  In this way you can get rid of this structure.

But again, we have listed a couple of options in the v13 discussion [1]:

1) Call kvm_ops_update() twice before and after hardware_setup() in order to use
hardware_enable_all() directly.

2) Expose kvm_x86_ops as symbol so VMX can set hardware_{enable|disable}()
callback before hardware_setup() in order to use hardware_enable_all().

3) Implement VMX's own hardware_enable_all() logic as shown in this patch.

4) ???

I think it would be better if Sean can provide some comments here, but until he
does, we can keep using option 3) (this patch).

[1]
https://lore.kernel.org/lkml/5dc84a2601a47ccc29ef43200cf3ec0d1b485d23.camel@intel.com/