linux-kernel - Re: [PATCH v2 2/3] KVM: VMX: Replace MSR_IA32_RTIT_OUTPUT_BASE

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Message-ID: <20200924180120.GA9649@linux.intel.com>
Date:   Thu, 24 Sep 2020 11:01:20 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] KVM: VMX: Replace MSR_IA32_RTIT_OUTPUT_BASE_MASK
 with helper function

On Wed, Sep 23, 2020 at 07:07:22PM +0200, Paolo Bonzini wrote:
> On 23/09/20 18:36, Sean Christopherson wrote:
> > +static inline bool pt_output_base_valid(struct kvm_vcpu *vcpu, u64 base)
> > +{
> > +	/* The base must be 128-byte aligned and a legal physical address. */
> > +	return !(base & (~((1UL << cpuid_maxphyaddr(vcpu)) - 1) | 0x7f));
> > +}
> 
> The fact that you deemed a comment necessary says something already. :)
> What about:
> 
>         return !kvm_mmu_is_illegal_gpa(vcpu, base) && !(base & 0x7f);
> 
> (where this new usage makes it obvious that mmu should have been vcpu).

Ya.  I think it was a sort of sunk cost fallacy.  Dammit, I spent all that
time figuring out what this code does, I'm keeping it!!!

v3 incoming...