From: olof@lixom•net (Olof Johansson)
To: Luke Browning <lukebr@linux•vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba•org>,
cbe-oss-dev@ozlabs•org, Arnd Bergmann <arnd@arndb•de>,
linuxppc-dev@ozlabs•org
Subject: Re: [PATCH] 64K page support for kexec
Date: Tue, 24 Apr 2007 14:43:48 -0500 [thread overview]
Message-ID: <20070424194348.GA8371@lixom.net> (raw)
In-Reply-To: <1177439513.24866.5.camel@luke-laptop>
Hi,
Didn't see this posted before, but see some comments below.
Thanks,
Olof
On Tue, Apr 24, 2007 at 03:31:53PM -0300, Luke Browning wrote:
> +#define LP_SHIFT 12
> +#define LP_BITS 8
> +#define LP_MASK(i) ((((1 << LP_BITS) - 1) >> (i)) << LP_SHIFT)
Seems to me that something like:
#define LP_MASK(i) ((0xff >> (i)) << LP_SHIFT)
is considerably easier to read.
> +static void hpte_decode(hpte_t *hpte, unsigned long slot,
> + int *psize, unsigned long *va)
> +{
> + unsigned long hpte_r = hpte->r;
> + unsigned long hpte_v = hpte->v;
> + unsigned long avpn;
> + int i, size, shift, penc, avpnm_bits;
> +
> + if (!(hpte_v & HPTE_V_LARGE))
> + size = MMU_PAGE_4K;
> +#if 0
> + else if (hpte_v & 0x4000000000000000UL)
> + size = MMU_PAGE_16G;
> +#endif
No ifdefs please. Just take it out if it's not needed.
> + else if (!(hpte_r & LP_MASK(0)))
> + size = MMU_PAGE_16M;
> + else {
> + for (i = 0; i < LP_BITS; i++) {
> + if ((hpte_r & LP_MASK(i+1)) == LP_MASK(i+1))
> + break;
> + }
> + penc = LP_MASK(i+1) >> LP_SHIFT;
No need for braces. Also, why iterate from 0 to LP_BITS if you're doing i+1 everywhere?
> + for (size = MMU_PAGE_64K; size < MMU_PAGE_16M; size++) {
This assumes that the page sizes are ordered. Why not just iterate from
0 to MMU_PAGE_COUNT?
> + if (!mmu_psize_defs[size].shift)
> + continue;
A comment to the effect of "unused entries have a shift value of 0" could be
useful.
> + if (penc == mmu_psize_defs[size].penc)
> + break;
> + }
> + }
>
> - vpi = ((va >> 28) ^ pteg) & htab_hash_mask;
> + /*
> + * FIXME, this could be made more efficient by storing the type
> + * of hash algorithm in mmu_psize_defs[]. The code below assumes
> + * the number of bits in the va representing the offset in the
> + * page is less than 23. This affects the hash algorithm that is
> + * used. When 16G pages are supported, a new hash algorithm
> + * needs to be provided. See POWER ISA Book III.
> + *
> + * The code below works for 16M, 64K, and 4K pages.
> + */
A BUG_ON() when other sizes are hit could be a good idea?
> + shift = mmu_psize_defs[size].shift;
> + if (mmu_psize_defs[size].avpnm)
> + avpnm_bits = __ilog2_u64(mmu_psize_defs[size].avpnm) + 1;
> + else
> + avpnm_bits = 0;
> + if (shift - avpnm_bits <= 23) {
> + avpn = HPTE_V_AVPN_VAL(hpte_v) << 23;
> +
> + if (shift < 23) {
> + unsigned long vpi, pteg;
> +
> + pteg = slot / HPTES_PER_GROUP;
> + if (hpte_v & HPTE_V_SECONDARY)
> + pteg = ~pteg;
> + vpi = ((avpn >> 28) ^ pteg) & htab_hash_mask;
> + avpn |= (vpi << mmu_psize_defs[size].shift);
> + }
> + }
> +#if 0
> + /* 16GB page hash, p > 23 */
> + else {
Same thing here w.r.t. ifdefs
>
> - va |= vpi << PAGE_SHIFT;
> }
> +#endif
>
> - return va;
> + *va = avpn;
> + *psize = size;
> }
>
> /*
> @@ -374,8 +420,6 @@ static unsigned long slot2va(unsigned lo
> *
> * TODO: add batching support when enabled. remember, no dynamic memory here,
> * athough there is the control page available...
> - *
> - * XXX FIXME: 4k only for now !
> */
> static void native_hpte_clear(void)
> {
> @@ -383,6 +427,7 @@ static void native_hpte_clear(void)
> hpte_t *hptep = htab_address;
> unsigned long hpte_v;
> unsigned long pteg_count;
> + int psize;
>
> pteg_count = htab_hash_mask + 1;
>
> @@ -408,8 +453,9 @@ static void native_hpte_clear(void)
> * already hold the native_tlbie_lock.
> */
> if (hpte_v & HPTE_V_VALID) {
> + hpte_decode(hptep, slot, &psize, &hpte_v);
> hptep->v = 0;
> - __tlbie(slot2va(hpte_v, slot), MMU_PAGE_4K);
> + __tlbie(hpte_v, psize);
Using hpte_v as variable name is a bit misleading. avpn or va would be
a better variable name.
-Olof
next prev parent reply other threads:[~2007-04-24 19:43 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-24 18:31 [PATCH] 64K page support for kexec Luke Browning
2007-04-24 19:43 ` Olof Johansson [this message]
2007-04-24 22:50 ` Benjamin Herrenschmidt
2007-04-24 23:07 ` Olof Johansson
2007-04-25 5:48 ` Milton Miller
2007-04-25 19:35 ` [PATCH v2] powerpc: " Luke Browning
2007-04-25 22:19 ` Benjamin Herrenschmidt
2007-04-26 15:28 ` Luke Browning
2007-04-27 4:36 ` [PATCH v3] " Milton Miller
2007-04-27 14:42 ` Luke Browning
2007-04-27 16:51 ` Milton Miller
2007-04-27 16:22 ` [PATCH v4] " Luke Browning
2007-04-27 16:59 ` Milton Miller
2007-04-27 17:30 ` Luke Browning
2007-04-27 18:23 ` Haren Myneni
2007-04-29 5:35 ` Milton Miller
2007-04-29 8:30 ` Paul Mackerras
2007-04-29 9:31 ` Benjamin Herrenschmidt
2007-04-29 13:27 ` Segher Boessenkool
2007-04-29 22:49 ` Benjamin Herrenschmidt
2007-04-26 7:15 ` [PATCH v2] " Olof Johansson
2007-04-24 22:48 ` [PATCH] " Benjamin Herrenschmidt
2007-04-25 13:06 ` Luke Browning
2007-04-25 22:11 ` Benjamin Herrenschmidt
-- strict thread matches above, loose matches on Subject: below --
2007-04-26 22:23 [PATCH v3] powerpc: " Luke Browning
2007-04-26 22:32 ` Olof Johansson
2007-05-02 14:19 ` [PATCH v4] " Luke Browning
2007-05-03 13:45 ` Arnd Bergmann
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