linux-kernel - Re: [PATCH v2 24/25] KVM: x86: Introduce KVM_TDX_GET

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Message-ID: <2227406cbc6ca249c78e886c301dd39064053cc4.camel@intel.com>
Date: Tue, 21 Jan 2025 20:24:44 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Li, Xiaoyao" <xiaoyao.li@...el.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>
CC: "Huang, Kai" <kai.huang@...el.com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "Chatre, Reinette" <reinette.chatre@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "isaku.yamahata@...il.com"
	<isaku.yamahata@...il.com>, "tony.lindgren@...ux.intel.com"
	<tony.lindgren@...ux.intel.com>
Subject: Re: [PATCH v2 24/25] KVM: x86: Introduce KVM_TDX_GET_CPUID

On Fri, 2025-01-10 at 12:47 +0800, Xiaoyao Li wrote:
> 0x1f needs clarification here.
> 
> If it's going to use the maximum leaf KVM can support, it should be 0x24 
> to align with __do_cpuid_func().
> 
> alternatively, it can use the EAX value of leaf 0 returned by TDX 
> module. That is the value TDX module presents to the TD guest.
> 
> > +		output_e = &td_cpuid->entries[i];
> > +		i += tdx_vcpu_get_cpuid_leaf(vcpu, leaf,
> > +					     KVM_MAX_CPUID_ENTRIES - i - 1,
> > +					     output_e);
> > +	}
> > +
> > +	for (leaf = 0x80000000; leaf <= 0x80000008; leaf++) {
> > +		output_e = &td_cpuid->entries[i];
> > +		i += tdx_vcpu_get_cpuid_leaf(vcpu, leaf,
> > +					     KVM_MAX_CPUID_ENTRIES - i - 1,
> > +					     output_e);

Since we are not filtering by KVM supported features anymore, maybe just use the
max leaf for the host CPU, like:

@@ -2790,14 +2791,14 @@ static int tdx_vcpu_get_cpuid(struct kvm_vcpu *vcpu,
struct kvm_tdx_cmd *cmd)
        if (!td_cpuid)
                return -ENOMEM;
 
-       for (leaf = 0; leaf <= 0x1f; leaf++) {
+       for (leaf = 0; leaf <= boot_cpu_data.cpuid_level; leaf++) {
                output_e = &td_cpuid->entries[i];
                i += tdx_vcpu_get_cpuid_leaf(vcpu, leaf,
                                             KVM_MAX_CPUID_ENTRIES - i - 1,
                                             output_e);
        }
 
-       for (leaf = 0x80000000; leaf <= 0x80000008; leaf++) {
+       for (leaf = 0x80000000; leaf <= boot_cpu_data.extended_cpuid_level;
leaf++) {
                output_e = &td_cpuid->entries[i];
                i += tdx_vcpu_get_cpuid_leaf(vcpu, leaf,
                                             KVM_MAX_CPUID_ENTRIES - i - 1,