linux-kernel - Re: [RFC PATCH v5 045/104] KVM: x86/tdp_mmu: make REMOVED_SPTE include shadow

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Message-ID: <Yk4j0cCR5fnQKw1F@google.com>
Date:   Wed, 6 Apr 2022 23:35:45 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>
Subject: Re: [RFC PATCH v5 045/104] KVM: x86/tdp_mmu: make REMOVED_SPTE
 include shadow_initial value

On Tue, Apr 05, 2022, Paolo Bonzini wrote:
> On 3/4/22 20:49, isaku.yamahata@...el.com wrote:
> > @@ -207,9 +209,17 @@ extern u64 __read_mostly shadow_nonpresent_or_rsvd_mask;
> >   /* Removed SPTEs must not be misconstrued as shadow present PTEs. */
> >   static_assert(!(REMOVED_SPTE & SPTE_MMU_PRESENT_MASK));
> > +/*
> > + * See above comment around REMOVED_SPTE.  SHADOW_REMOVED_SPTE is the actual
> > + * intermediate value set to the removed SPET.  When TDX is enabled, it sets
> > + * the "suppress #VE" bit, otherwise it's REMOVED_SPTE.
> > + */
> > +extern u64 __read_mostly shadow_init_value;
> > +#define SHADOW_REMOVED_SPTE	(shadow_init_value | REMOVED_SPTE)
> 
> Please rename the existing REMOVED_SPTE to REMOVED_SPTE_MASK, and call this
> simply REMOVED_SPTE.  This also makes the patch smaller.

Can we name it either __REMOVE_SPTE or REMOVED_SPTE_VAL?  It's most definitely
not a mask, it's a full value, e.g. spte |= REMOVED_SPTE_MASK is completely wrong.

Other than that, 100% agree with avoiding churn.