[PATCH] ARM: VIPT cache coherency fix

[Imre Deak <imre.deak%teleca.com@localhost>]

Currently page loaning (at least) is broken on ARM VIPT platforms.
The reason is that possible dirty cache lines are not taken into account
at the moment, following is a fix for this.

The fix is validated against the latest breakage related to the socket
page loaning reported earlier on the list.

--Imre

diff --git a/sys/arch/arm/arm32/pmap.c b/sys/arch/arm/arm32/pmap.c
index 2b62477..3ed914d 100644
--- a/sys/arch/arm/arm32/pmap.c
+++ b/sys/arch/arm/arm32/pmap.c
@@ -877,6 +877,7 @@ pmap_enter_pv(struct vm_page *pg, struct pv_entry *pve, 
pmap_t pm,
                pg->mdpage.uro_mappings++;
 
 #ifdef PMAP_CACHE_VIPT
+       pmap_vac_me_harder(pg, pm, va);
        /*
         * If this is an exec mapping and its the first exec mapping
         * for this page, make sure to sync the I-cache.
@@ -1833,6 +1834,7 @@ pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, vaddr_t 
va)
        /* Already a conflict? */
        if (__predict_false(pg->mdpage.pvh_attrs & PVF_NC)) {
                /* just an add, things are already non-cached */
+               KASSERT(!(pg->mdpage.pvh_attrs & PVF_DIRTY));
                bad_alias = false;
                if (va) {
                        PMAPCOUNT(vac_color_none);
@@ -1849,17 +1851,21 @@ pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, 
vaddr_t va)
                        tst_mask = pv->pv_va;
                        pv = pv->pv_next;
                }
+
+               tst_mask &= arm_cache_prefer_mask;
+
                /*
                 * Only check for a bad alias if we have writable mappings.
                 */
                if (pg->mdpage.urw_mappings + pg->mdpage.krw_mappings > 0) {
-                       tst_mask &= arm_cache_prefer_mask;
                        for (; pv && !bad_alias; pv = pv->pv_next) {
                                /* if there's a bad alias, stop checking. */
                                if (tst_mask != (pv->pv_va & 
arm_cache_prefer_mask))
                                        bad_alias = true;
                        }
                        pg->mdpage.pvh_attrs |= PVF_WRITE;
+                       if (!bad_alias)
+                               pg->mdpage.pvh_attrs |= PVF_DIRTY;
                }
                /* If no conflicting colors, set everything back to cached */
                if (!bad_alias) {
@@ -1873,19 +1879,21 @@ pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, 
vaddr_t va)
                KASSERT((pg->mdpage.urw_mappings + pg->mdpage.krw_mappings == 
0) == !(pg->mdpage.pvh_attrs & PVF_WRITE));
        } else if (!va) {
                KASSERT(pmap_is_page_colored_p(pg));
-               pg->mdpage.pvh_attrs &= (PAGE_SIZE - 1) | arm_cache_prefer_mask;
+               KASSERT(!(pg->mdpage.pvh_attrs & PVF_WRITE) ||
+                        (pg->mdpage.pvh_attrs & PVF_DIRTY));
                if (pg->mdpage.urw_mappings + pg->mdpage.krw_mappings == 0)
                        pg->mdpage.pvh_attrs &= ~PVF_WRITE;
                KASSERT((pg->mdpage.urw_mappings + pg->mdpage.krw_mappings == 
0) == !(pg->mdpage.pvh_attrs & PVF_WRITE));
                return;
        } else if (!pmap_is_page_colored_p(pg)) {
+               KASSERT(!(pg->mdpage.pvh_attrs & (PVF_WRITE | PVF_DIRTY)));
                /* not colored so we just use its color */
                PMAPCOUNT(vac_color_new);
                pg->mdpage.pvh_attrs &= PAGE_SIZE - 1;
                pg->mdpage.pvh_attrs |= PVF_COLORED
                    | (va & arm_cache_prefer_mask);
                if (pg->mdpage.urw_mappings + pg->mdpage.krw_mappings > 0)
-                       pg->mdpage.pvh_attrs |= PVF_WRITE;
+                       pg->mdpage.pvh_attrs |= PVF_WRITE | PVF_DIRTY;
                KASSERT((pg->mdpage.urw_mappings + pg->mdpage.krw_mappings == 
0) == !(pg->mdpage.pvh_attrs & PVF_WRITE));
                return;
        } else if (((pg->mdpage.pvh_attrs ^ va) & arm_cache_prefer_mask) == 0) {
@@ -1908,6 +1916,8 @@ pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, vaddr_t 
va)
                                }
                        }
                        pg->mdpage.pvh_attrs |= PVF_WRITE;
+                       if (!bad_alias)
+                               pg->mdpage.pvh_attrs |= PVF_DIRTY;
                }
                /* If no conflicting colors, set everything back to cached */
                if (!bad_alias) {
@@ -1925,14 +1935,20 @@ pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, 
vaddr_t va)
                /* color conflict.  evict from cache. */
 
                pmap_flush_page(pg);
-               pg->mdpage.pvh_attrs &= ~PVF_COLORED;
+               pg->mdpage.pvh_attrs &= ~(PVF_COLORED | PVF_DIRTY);
                pg->mdpage.pvh_attrs |= PVF_NC;
        } else if (pg->mdpage.urw_mappings + pg->mdpage.krw_mappings == 0
                   && (pg->mdpage.pvh_attrs & PVF_KMPAGE) == 0) {
                KASSERT((pg->mdpage.pvh_attrs & PVF_WRITE) == 0);
-               /*
-                * If all the mappings are read-only, don't do anything.
-                */
+               if (pg->mdpage.pvh_attrs & PVF_DIRTY) {
+                       /*
+                        * Flush the page b/c there might be dirty
+                        * cache lines.
+                        */
+                       pmap_flush_page(pg);
+                       pg->mdpage.pvh_attrs &= (PAGE_SIZE - 1) & ~PVF_DIRTY;
+                       pg->mdpage.pvh_attrs |= va & arm_cache_prefer_mask;
+               }
                PMAPCOUNT(vac_color_blind);
                KASSERT((pg->mdpage.urw_mappings + pg->mdpage.krw_mappings == 
0) == !(pg->mdpage.pvh_attrs & PVF_WRITE));
                return;
@@ -1942,6 +1958,7 @@ pmap_vac_me_harder(struct vm_page *pg, pmap_t pm, vaddr_t 
va)
 
                /* color conflict.  evict from cache. */
                pmap_flush_page(pg);
+               pg->mdpage.pvh_attrs &= ~PVF_DIRTY;
 
                /* the list can't be empty because this was a enter/modify */
                pv = pg->mdpage.pvh_list;
@@ -2694,6 +2711,7 @@ pmap_enter(pmap_t pm, vaddr_t va, paddr_t pa, vm_prot_t 
prot, int flags)
                        oflags = pmap_modify_pv(pg, pm, va,
                            PVF_WRITE | PVF_EXEC | PVF_WIRED |
                            PVF_MOD | PVF_REF, nflags);
+                       pmap_vac_me_harder(pg, pm, va);
                        simple_unlock(&pg->mdpage.pvh_slock);
 
 #ifdef PMAP_CACHE_VIVT