arch/tile: support 4KB page size as well as 64KB

The Tilera architecture traditionally supports 64KB page sizes
to improve TLB utilization and improve performance when the
hardware is being used primarily to run a single application.

For more generic server scenarios, it can be beneficial to run
with 4KB page sizes, so this commit allows that to be specified
(by modifying the arch/tile/include/hv/pagesize.h header).

As part of this change, we also re-worked the PTE management
slightly so that PTE writes all go through a __set_pte() function
where we can do some additional validation.  The set_pte_order()
function was eliminated since the "order" argument wasn't being used.

One bug uncovered was in the PCI DMA code, which wasn't properly
flushing the specified range.  This was benign with 64KB pages,
but with 4KB pages we were getting some larger flushes wrong.

The per-cpu memory reservation code also needed updating to
conform with the newer percpu stuff; before it always chose 64KB,
and that was always correct, but with 4KB granularity we now have
to pay closer attention and reserve the amount of memory that will
be requested when the percpu code starts allocating.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 1 insertions, 17 deletions

diff --git a/arch/tile/mm/init.c b/arch/tile/mm/init.c
index f89ed5d..d6e87fd 100644
--- a/arch/tile/mm/init.c
+++ b/arch/tile/mm/init.c
@@ -53,18 +53,6 @@
 
 #include "migrate.h"
 
-/*
- * We could set FORCE_MAX_ZONEORDER to "(HPAGE_SHIFT - PAGE_SHIFT + 1)"
- * in the Tile Kconfig, but this generates configure warnings.
- * Do it here and force people to get it right to compile this file.
- * The problem is that with 4KB small pages and 16MB huge pages,
- * the default value doesn't allow us to group enough small pages
- * together to make up a huge page.
- */
-#if CONFIG_FORCE_MAX_ZONEORDER < HPAGE_SHIFT - PAGE_SHIFT + 1
-# error "Change FORCE_MAX_ZONEORDER in arch/tile/Kconfig to match page size"
-#endif
-
 #define clear_pgd(pmdptr) (*(pmdptr) = hv_pte(0))
 
 #ifndef __tilegx__
@@ -962,11 +950,7 @@ struct kmem_cache *pgd_cache;
 
 void __init pgtable_cache_init(void)
 {
-	pgd_cache = kmem_cache_create("pgd",
-				PTRS_PER_PGD*sizeof(pgd_t),
-				PTRS_PER_PGD*sizeof(pgd_t),
-				0,
-				NULL);
+	pgd_cache = kmem_cache_create("pgd", SIZEOF_PGD, SIZEOF_PGD, 0, NULL);
 	if (!pgd_cache)
 		panic("pgtable_cache_init(): Cannot create pgd cache");
 }