linux-kernel - Re: [PATCH v2] KVM: vmx: add mismatched size assertions in vmcs

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Date:   Sat, 17 Apr 2021 15:17:47 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     lihaiwei.kernel@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org,
        Haiwei Li <lihaiwei@...cent.com>
Subject: Re: [PATCH v2] KVM: vmx: add mismatched size assertions in
 vmcs_check32()

On 09/04/21 04:24, lihaiwei.kernel@...il.com wrote:
> From: Haiwei Li <lihaiwei@...cent.com>
> 
> Add compile-time assertions in vmcs_check32() to disallow accesses to
> 64-bit and 64-bit high fields via vmcs_{read,write}32().  Upper level KVM
> code should never do partial accesses to VMCS fields.  KVM handles the
> split accesses automatically in vmcs_{read,write}64() when running as a
> 32-bit kernel.
> 
> Reviewed-and-tested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Haiwei Li <lihaiwei@...cent.com>
> ---
> v1 -> v2:
> * Improve the changelog
> 
>   arch/x86/kvm/vmx/vmx_ops.h | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h
> index 692b0c3..164b64f 100644
> --- a/arch/x86/kvm/vmx/vmx_ops.h
> +++ b/arch/x86/kvm/vmx/vmx_ops.h
> @@ -37,6 +37,10 @@ static __always_inline void vmcs_check32(unsigned long field)
>   {
>   	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
>   			 "32-bit accessor invalid for 16-bit field");
> +	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
> +			 "32-bit accessor invalid for 64-bit field");
> +	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
> +			 "32-bit accessor invalid for 64-bit high field");
>   	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
>   			 "32-bit accessor invalid for natural width field");
>   }
> 

Queued, thanks.

paolo