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

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Message-ID: <ZsLR8RxAsTT8yTUo@yilunxu-OptiPlex-7050>
Date: Mon, 19 Aug 2024 13:02:41 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org,
	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 Mon, Aug 12, 2024 at 03:48:19PM -0700, Rick Edgecombe wrote:
> Future TDX modules may provide support for future HW features, but run with
> KVM versions that lack support for them. In this case, userspace may try to
> use features that KVM does not have support, and develop assumptions around
> KVM's behavior. Then KVM would have to deal with not breaking such
> userspace.
> 
> Simplify KVM's job by preventing userspace from configuring any unsupported
> CPUID feature bits.
> 
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> ---
> uAPI breakout v1:
>  - New patch
> ---
>  arch/x86/kvm/vmx/tdx.c | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index c6bfeb0b3cc9..d45b4f7b69ba 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1086,8 +1086,9 @@ static int tdx_td_vcpu_init(struct kvm_vcpu *vcpu, u64 vcpu_rcx)
>  	return ret;
>  }
>  
> -static int __maybe_unused tdx_get_kvm_supported_cpuid(struct kvm_cpuid2 **cpuid)
> +static int tdx_get_kvm_supported_cpuid(struct kvm_cpuid2 **cpuid)

This func is already used in patch #21, put the change in that patch.

>  {
> +

remove the blank line.

>  	int r;

Thanks,
Yilun