linux-kernel - Re: [PATCH] KVM: VMX: Zero host's SYSENTER

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Date:   Mon, 24 Jan 2022 14:46:28 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>
Subject: Re: [PATCH] KVM: VMX: Zero host's SYSENTER_ESP iff SYSENTER is NOT
 used

On 1/22/22 09:47, Vitaly Kuznetsov wrote:
>>   	 */
>> -	vmcs_writel(HOST_IA32_SYSENTER_ESP, 0);
>> +	if (!IS_ENABLED(CONFIG_IA32_EMULATION) && !IS_ENABLED(CONFIG_X86_32))
> Isn't it the same as "!IS_ENABLED(CONFIG_COMPAT_32)"? (same goes to the
> check in vmx_vcpu_load_vmcs())
> 

It is, but I think it's clearer to write it as it's already done in 
arch/x86/kvm/vmx/vmx.c, or possibly

if (IS_ENABLED(CONFIG_X86_64) && !IS_ENABLED(CONFIG_IA32_EMULATION))

CONFIG_COMPAT_32 doesn't say as clearly whether it's enabled for 32-bit 
systems or not.

Paolo