linux-kernel - Re: [PATCH 24/25] KVM: x86: Filter directly configurable TDX CPUID bits

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Message-ID: <dc87af84-d531-4938-a525-9bbbf7d714ec@redhat.com>
Date: Tue, 10 Sep 2024 19:36:00 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>, seanjc@...gle.com,
 kvm@...r.kernel.org
Cc: kai.huang@...el.com, isaku.yamahata@...il.com,
 tony.lindgren@...ux.intel.com, xiaoyao.li@...el.com,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 24/25] KVM: x86: Filter directly configurable TDX CPUID
 bits

On 8/13/24 00:48, Rick Edgecombe wrote:
> +
> +		cpuid_e = kvm_find_cpuid_entry2(supported_cpuid->entries, supported_cpuid->nent,
> +						dest->leaf, dest->sub_leaf);
> +		if (!cpuid_e) {
> +			dest->eax = dest->ebx = dest->ecx = dest->edx = 0;
> +		} else {
> +			dest->eax &= cpuid_e->eax;
> +			dest->ebx &= cpuid_e->ebx;
> +			dest->ecx &= cpuid_e->ecx;
> +			dest->edx &= cpuid_e->edx;
> +		}

This can only work with CPUID entries that consists of 4*32 features, so 
it has to be done specifically for each leaf, unfortunately.  I suggest 
defining a kvm_merge_cpuid_entries in cpuid.c that takes two struct 
cpuid_entry2* that refer to the same leaf and subleaf.

Paolo