On Thu, Feb 21, 2013 at 10:17:15PM +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com>
>
> We look at both the segment base page size and actual page size and store
> the pte-lp-encodings in an array per base page size.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
This needs more than 2 lines of patch description. In fact what
you're doing is adding general mixed page-size segment (MPSS)
support. Doing this should mean that you can also get rid of the
MMU_PAGE_64K_AP value from the list in asm/mmu.h.
> struct mmu_psize_def
> {
> unsigned int shift; /* number of bits */
> - unsigned int penc; /* HPTE encoding */
> + unsigned int penc[MMU_PAGE_COUNT]; /* HPTE encoding */
I guess this is reasonable, though adding space for 14 page size
encodings seems a little bit over the top. Also, you don't seem to
have any way to indicate which encodings are valid, since 0 is a valid
encoding. Maybe you need to add a valid bit higher up to indicate
which page sizes are valid.
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 71d0c90..d2c9932 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1515,7 +1515,12 @@ static void kvmppc_add_seg_page_size(struct
> kvm_ppc_one_seg_page_size **sps,
> (*sps)->page_shift = def->shift;
> (*sps)->slb_enc = def->sllp;
> (*sps)->enc[0].page_shift = def->shift;
> - (*sps)->enc[0].pte_enc = def->penc;
> + /*
> + * FIXME!!
> + * This is returned to user space. Do we need to
> + * return details of MPSS here ?
Yes, we do, probably a separate entry for each valid base/actual page
size pair.
> +static inline int hpte_actual_psize(struct hash_pte *hptep, int psize)
> +{
> + unsigned int mask;
> + int i, penc, shift;
> + /* Look at the 8 bit LP value */
> + unsigned int lp = (hptep->r >> LP_SHIFT) & ((1 << (LP_BITS + 1)) - 1);
Why LP_BITS + 1 here? You seem to be extracting and comparing 9 bits
rather than 8. Why is that?
> @@ -395,12 +422,13 @@ static void hpte_decode(struct hash_pte *hpte, unsigned
> long slot,
> /* valid entries have a shift value */
> if (!mmu_psize_defs[size].shift)
> continue;
> -
> - if (penc == mmu_psize_defs[size].penc)
> - break;
> + for (a_size = 0; a_size < MMU_PAGE_COUNT; a_size++)
> + if (penc == mmu_psize_defs[size].penc[a_size])
> + goto out;
I think this will get false matches due to unused/invalid entries
in mmu_psize_defs[size].penc[] containing 0.
Paul.
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