Re: [PATCH 1/5] KVM: MMU: introduce some macros to cleanup hlisttraverseing

[Avi Kivity]

On 06/01/2010 05:38 AM, Xiao Guangrong wrote:
> Avi Kivity wrote:
>    
> > On 05/31/2010 05:00 AM, Xiao Guangrong wrote:
> >      
> > >        
> > > >          
> > > > > +
> > > > > +#define for_each_gfn_indirect_sp(kvm, sp, gfn, pos, n)            \
> > > > > +  hlist_for_each_entry_safe(sp, pos, n,                    \
> > > > > +&kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)], hash_link)\
> > > > > +        if (sp->gfn == gfn&&    !sp->role.direct)
> > > > > +
> > > > > +#define for_each_gfn_indirect_valid_sp(kvm, sp, gfn, pos, n)        \
> > > > > +  hlist_for_each_entry_safe(sp, pos, n,                    \
> > > > > +&kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)], hash_link)\
> > > > > +        if (sp->gfn == gfn&&    !sp->role.direct&&          \
> > > > > +            !sp->role.invalid)
> > > > >
> > > > >
> > > > >            
> > > > Shouldn't we always skip invalid gfns?
> > > >
> > > >          
> > > Actually, in kvm_mmu_unprotect_page() function, it need find out
> > > invalid shadow pages:
> > >
> > > |    hlist_for_each_entry_safe(sp, node, n, bucket, hash_link)
> > > |        if (sp->gfn == gfn&&   !sp->role.direct) {
> > > |            pgprintk("%s: gfn %lx role %x\n", __func__, gfn,
> > > |                 sp->role.word);
> > > |            r = 1;
> > > |            if (kvm_mmu_zap_page(kvm, sp))
> > > |                goto restart;
> > > |        }
> > >
> > > I'm not sure whether we can skip invalid sp here, since it can change
> > > this
> > > function's return value. :-(
> > >
> > >        
> > Hm.  Invalid pages don't need to be write protected.  So I think you can
> > patch unprotect_page() to ignore invalid pages, and then you can convert
> > it to the new macros which ignore invalid pages as well.
> >
> > The invariant is: if an sp exists with !role.invalid and !unsync, then
> > the page must be write protected.
> >      
> OK, will fix it in the next version.
>
>    
> >      
> > > > What about providing both gfn and role to the macro?
> > > >
> > > >
> > > >          
> > > In current code, no code simply use role and gfn to find sp,
> > > in kvm_mmu_get_page(), we need do other work for
> > > 'sp->gfn == gfn&&   sp->role != role' sp, and other functions only need
> > > compare
> > > some members in role, but not all members.
> > >
> > >        
> > How about just gfn?  I think everything compares against that!
> >
> >      
> In this patch, it already introduced a macro to only compares 'gfn', that is:
>
> +#define for_each_gfn_sp(kvm, sp, gfn, pos, n)				\
> +  hlist_for_each_entry_safe(sp, pos, n,				\
> +	&kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)], hash_link)\
> +		if (sp->gfn == gfn)
>
> Sorry if i misunderstand your meaning.
>    

No, I got confused.

--
error compiling committee.c: too many arguments to function

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