linux-kernel - Re: [PATCH 08/12] Documentation: kvm: tdx-tdp-mmu: Properly format nested list for EPT state machine

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Message-ID: <20220712193428.GL1379820@ls.amr.corp.intel.com>
Date:   Tue, 12 Jul 2022 12:34:28 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Bagas Sanjaya <bagasdotme@...il.com>
Cc:     linux-doc@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Kai Huang <kai.huang@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...il.com
Subject: Re: [PATCH 08/12] Documentation: kvm: tdx-tdp-mmu: Properly format
 nested list for EPT state machine

On Sat, Jul 09, 2022 at 11:26:26AM +0700,
Bagas Sanjaya <bagasdotme@...il.com> wrote:

> On Sat, Jul 09, 2022 at 11:20:34AM +0700, Bagas Sanjaya wrote:
> >  The state machine of EPT entry
> >  ------------------------------
> > -(private EPT entry, shared EPT entry) =
> > -        (non-present, non-present):             private mapping is allowed
> > -        (present, non-present):                 private mapping is mapped
> > -        (non-present | SPTE_SHARED_MASK, non-present | SPTE_SHARED_MASK):
> > -                                                shared mapping is allowed
> > -        (non-present | SPTE_SHARED_MASK, present | SPTE_SHARED_MASK):
> > -                                                shared mapping is mapped
> > -        (present | SPTE_SHARED_MASK, any)       invalid combination
> > +* (private EPT entry, shared EPT entry)
> >  
> > -* map_gpa(private GPA): Mark the region that private GPA is allowed(NEW)
> > -        private EPT entry: clear SPTE_SHARED_MASK
> > -          present: nop
> > -          non-present: nop
> > -          non-present | SPTE_SHARED_MASK -> non-present (clear SPTE_SHARED_MASK)
> > +  * (non-present, non-present):
> > +       private mapping is allowed
> > +  * (present, non-present):
> > +       private mapping is mapped
> > +  * (non-present | SPTE_SHARED_MASK, non-present | SPTE_SHARED_MASK):
> > +       shared mapping is allowed
> > +  * (non-present | SPTE_SHARED_MASK, present | SPTE_SHARED_MASK):
> > +       shared mapping is mapped
> > +  * (present | SPTE_SHARED_MASK, any):
> > +       invalid combination
> >  
> > -        shared EPT entry: zap the entry, clear SPTE_SHARED_MASK
> > -          present: invalid
> > -          non-present -> non-present: nop
> > -          present | SPTE_SHARED_MASK -> non-present
> > -          non-present | SPTE_SHARED_MASK -> non-present
> > +* map_gpa (private GPA): Mark the region that private GPA is allowed(NEW)
> >  
> > -* map_gpa(shared GPA): Mark the region that shared GPA is allowed(NEW)
> > -        private EPT entry: zap and set SPTE_SHARED_MASK
> > -          present     -> non-present | SPTE_SHARED_MASK
> > -          non-present -> non-present | SPTE_SHARED_MASK
> > -          non-present | SPTE_SHARED_MASK: nop
> > +  * private EPT entry: clear SPTE_SHARED_MASK
> >  
> > -        shared EPT entry: set SPTE_SHARED_MASK
> > -          present: invalid
> > -          non-present -> non-present | SPTE_SHARED_MASK
> > -          present | SPTE_SHARED_MASK -> present | SPTE_SHARED_MASK: nop
> > -          non-present | SPTE_SHARED_MASK -> non-present | SPTE_SHARED_MASK: nop
> > +    * present: nop
> > +    * non-present: nop
> > +    * non-present | SPTE_SHARED_MASK -> non-present (clear SPTE_SHARED_MASK)
> >  
> > -* map(private GPA)
> > -        private EPT entry
> > -          present: nop
> > -          non-present -> present
> > -          non-present | SPTE_SHARED_MASK: nop. looping on EPT violation(NEW)
> > +  * shared EPT entry: zap the entry, clear SPTE_SHARED_MASK
> >  
> > -        shared EPT entry: nop
> > +    * present: invalid
> > +    * non-present -> non-present: nop
> > +    * present | SPTE_SHARED_MASK -> non-present
> > +    * non-present | SPTE_SHARED_MASK -> non-present
> >  
> > -* map(shared GPA)
> > -        private EPT entry: nop
> > +* map_gpa (shared GPA): Mark the region that shared GPA is allowed(NEW)
> >  
> > -        shared EPT entry
> > -          present: invalid
> > -          present | SPTE_SHARED_MASK: nop
> > -          non-present | SPTE_SHARED_MASK -> present | SPTE_SHARED_MASK
> > -          non-present: nop. looping on EPT violation(NEW)
> > +  * private EPT entry: zap and set SPTE_SHARED_MASK
> >  
> > -* zap(private GPA)
> > -        private EPT entry: zap the entry with keeping SPTE_SHARED_MASK
> > -          present -> non-present
> > -          present | SPTE_SHARED_MASK: invalid
> > -          non-present: nop as is_shadow_present_pte() is checked
> > -          non-present | SPTE_SHARED_MASK: nop as is_shadow_present_pte() is
> > -                                          checked
> > +    * present     -> non-present | SPTE_SHARED_MASK
> > +    * non-present -> non-present | SPTE_SHARED_MASK
> > +    * non-present | SPTE_SHARED_MASK: nop
> >  
> > -        shared EPT entry: nop
> > +  * shared EPT entry: set SPTE_SHARED_MASK
> >  
> > -* zap(shared GPA)
> > -        private EPT entry: nop
> > +    * present: invalid
> > +    * non-present -> non-present | SPTE_SHARED_MASK
> > +    * present | SPTE_SHARED_MASK -> present | SPTE_SHARED_MASK: nop
> > +    * non-present | SPTE_SHARED_MASK -> non-present | SPTE_SHARED_MASK: nop
> >  
> > -        shared EPT entry: zap
> > -          any -> non-present
> > -          present: invalid
> > -          present | SPTE_SHARED_MASK -> non-present | SPTE_SHARED_MASK
> > -          non-present: nop as is_shadow_present_pte() is checked
> > -          non-present | SPTE_SHARED_MASK: nop as is_shadow_present_pte() is
> > -                                          checked
> > +* map (private GPA)
> > +
> > +  * private EPT entry
> > +
> > +    * present: nop
> > +    * non-present -> present
> > +    * non-present | SPTE_SHARED_MASK: nop. looping on EPT violation(NEW)
> > +
> > +  * shared EPT entry: nop
> > +
> > +* map (shared GPA)
> > +
> > +  * private EPT entry: nop
> > +
> > +  * shared EPT entry:
> > +
> > +    * present: invalid
> > +    * present | SPTE_SHARED_MASK: nop
> > +    * non-present | SPTE_SHARED_MASK -> present | SPTE_SHARED_MASK
> > +    * non-present: nop. looping on EPT violation(NEW)
> > +
> > +* zap (private GPA)
> > +
> > +  * private EPT entry: zap the entry with keeping SPTE_SHARED_MASK
> > +
> > +    * present -> non-present
> > +    * present | SPTE_SHARED_MASK: invalid
> > +    * non-present: nop as is_shadow_present_pte() is checked
> > +    * non-present | SPTE_SHARED_MASK: nop as is_shadow_present_pte() is
> > +      checked
> > +
> > +  * shared EPT entry: nop
> > +
> > +* zap (shared GPA)
> > +
> > +  * private EPT entry: nop
> > +
> > +  * shared EPT entry: zap
> > +
> > +    * any -> non-present
> > +    * present: invalid
> > +    * present | SPTE_SHARED_MASK -> non-present | SPTE_SHARED_MASK
> > +    * non-present: nop as is_shadow_present_pte() is checked
> > +    * non-present | SPTE_SHARED_MASK: nop as is_shadow_present_pte() is
> > +      checked
> 
> IMO, the state machine lists above should have used tables instead.

Makes sense. I'll convert those into tables.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>