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    SubjectRe: [PATCH 04/13] KVM: MMU: introduce FNAME(get_sp_gpa)
    On 03/30/2012 08:01 AM, Xiao Guangrong wrote:
    > On 03/29/2012 09:07 PM, Avi Kivity wrote:
    >
    > > On 03/29/2012 11:22 AM, Xiao Guangrong wrote:
    > >> It can calculate the base gpa of the specified shadow page on any level,
    > >> let it instead of FNAME(get_level1_sp_gpa)
    > >>
    > >>
    > >> +static gpa_t FNAME(get_sp_gpa)(struct kvm_mmu_page *sp)
    > >> +{
    > >
    > > Maybe worth adding a pte index and calling it get_spte_gpa(), depends on
    > > the next patches I guess.
    > >
    >
    >
    > Yes.
    >
    > But FNAME(get_sp_gpa) is still needed by FNAME(sync_page) path which sync
    > all sptes. I will introduce get_spte_gpa() as you mentioned which will be
    > used in invlpg path and in the later patch.
    >
    >
    > >> + int offset, shift;
    > >> +
    > >> + shift = PAGE_SHIFT - (PT_LEVEL_BITS - PT64_LEVEL_BITS) * sp->role.level;
    > >> + offset = sp->role.quadrant << shift;
    > >
    > > if you add '& ~PAGE_MASK' the compiler may be smart enough to drop the
    > > whole thing for 64-bit ptes.
    > >
    >
    >
    > Sorry. how to do that?

    offset = (sp->role.quadrant << shift) & ~PAGEMASK;

    the compiler should see that shift == PAGE_SHIFT and therefore anything
    in sp->role.quadrant will be masked out.

    > But if you want to remove the unnecessary workload, i will change it
    > like this:
    >
    > static gpa_t FNAME(get_sp_gpa)(struct kvm_mmu_page *sp)
    > {
    > int offset = 0;
    >
    > #if PTTYPE == 32
    > int shift;
    >
    > shift = PAGE_SHIFT - (PT_LEVEL_BITS - PT64_LEVEL_BITS) * sp->role.level;
    > offset = sp->role.quadrant << shift;
    > #endif
    > return gfn_to_gpa(sp->gfn) + offset;
    > }

    That works too.

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



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