linux-kernel - Re: [PATCH 3/4] KVM: X86: Handle implicit supervisor access with SMAP

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Date:   Wed, 8 Dec 2021 10:12:10 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 3/4] KVM: X86: Handle implicit supervisor access with SMAP

On 12/7/21 22:52, Sean Christopherson wrote:
>> -	unsigned long not_smap = (cpl - 3) & (rflags & X86_EFLAGS_AC);
>> +	u32 not_smap = (rflags & X86_EFLAGS_AC) & vcpu->arch.explicit_access;
> I really, really dislike shoving this into vcpu->arch.  I'd much prefer to make
> this a property of the access, even if that means adding another param or doing
> something gross with @access (@pfec here).
> 

Well, we already have something gross going on with the pfec.  Maybe we 
should add separate constants for the index into mmu->permissions.

Paolo