Changeset 976c434 in mainline

Timestamp:

2013-02-17T17:45:53Z (12 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

2b95d13

Parents:

192a23f0

Message:

Streamline TLB miss handling.

• Do one thing at a time.
• If the page is mapped in the page tables, insert it into TLB.
• If the page is not mapped in the page tables, call as_page_fault() and return.

File:

• kernel/arch/mips32/src/mm/tlb.c (modified) (11 diffs)

kernel/arch/mips32/src/mm/tlb.c

@@ -57 +57 @@
         
 
-static pte_t *find_mapping_and_check(uintptr_t, int, istate_t *);
-
 /** Initialize TLB.
  *
@@ -86 +84 @@
 }
 
-/** Verify the TLB still contains / does not contain a given entry after the
- * current thread possibly blocked.
- *
- * @param hi           Remembered contents of the EntryHi register.
- * @param should_exist Flag saying whether the caller expect the entry to exist
- *                     or not to exist.
- * @returns            True if the TLB contains or does not contain the mapping
- *                     according to the caller's expectation.
- * @returns            False otherwise.
- */
-static bool tlb_recheck_entry(entry_hi_t hi, bool should_exist)
-{
-        tlb_index_t index;
-
-        cp0_entry_hi_write(hi.value);
-        tlbp();
-        index.value = cp0_index_read();
-
-        if (!(should_exist ^ index.p)) {
-                /* The old entry disappeared or the new entry already exists. */
-                return false;
-        }
-
-        return true;
-}
-
 /** Process TLB Refill Exception.
  *
@@ -118 +90 @@
 void tlb_refill(istate_t *istate)
 {
-        entry_hi_t hi;
         entry_lo_t lo;
         uintptr_t badvaddr;
@@ -124 +95 @@
         
         badvaddr = cp0_badvaddr_read();
-        hi.value = cp0_entry_hi_read(); 
-
-        /* We may block in find_mapping_and_check(). */
-        pte = find_mapping_and_check(badvaddr, PF_ACCESS_READ, istate);
-        if (pte) {
-                if (!tlb_recheck_entry(hi, false))
-                        return;
-
+
+        pte = page_mapping_find(AS, badvaddr, true);
+        if (pte && pte->p) {
                 /*
                  * Record access to PTE.
@@ -152 +118 @@
                 cp0_pagemask_write(TLB_PAGE_MASK_16K);
                 tlbwr();
-        }
+                return;
+        }
+
+        (void) as_page_fault(badvaddr, PF_ACCESS_READ, istate);
 }
 
@@ -161 +130 @@
 void tlb_invalid(istate_t *istate)
 {
-        entry_hi_t hi;
         entry_lo_t lo;
         tlb_index_t index;
@@ -188 +156 @@
 
         badvaddr = cp0_badvaddr_read();
-        hi.value = cp0_entry_hi_read();
-
-        /* We may block in find_mapping_and_check(). */
-        pte = find_mapping_and_check(badvaddr, PF_ACCESS_READ, istate);
-        if (pte) {
-                if (!tlb_recheck_entry(hi, true))
-                        return;
-
+
+        pte = page_mapping_find(AS, badvaddr, true);
+        if (pte && pte->p) {
                 /*
                  * Read the faulting TLB entry.
@@ -217 +180 @@
                         cp0_entry_lo1_write(lo.value);
                 tlbwi();
-        }
+                return;
+        }
+
+        (void) as_page_fault(badvaddr, PF_ACCESS_READ, istate);
 }
 
@@ -226 +192 @@
 void tlb_modified(istate_t *istate)
 {
-        entry_hi_t hi;
         entry_lo_t lo;
         tlb_index_t index;
@@ -244 +209 @@
 
         badvaddr = cp0_badvaddr_read();
-        hi.value = cp0_entry_hi_read();
-
-        /* We may block in find_mapping_and_check(). */
-        pte = find_mapping_and_check(badvaddr, PF_ACCESS_WRITE, istate);
-        if (pte) {
-                if (!tlb_recheck_entry(hi, true))
-                        return;
-
+
+        pte = page_mapping_find(AS, badvaddr, true);
+        if (pte && pte->p && pte->w) {
                 /*
                  * Read the faulting TLB entry.
@@ -274 +234 @@
                         cp0_entry_lo1_write(lo.value);
                 tlbwi();
-        }
-}
-
-/** Try to find PTE for faulting address.
- *
- * @param badvaddr      Faulting virtual address.
- * @param access        Access mode that caused the fault.
- * @param istate        Pointer to interrupted state.
- *
- * @return              PTE on success, NULL otherwise.
- */
-pte_t *find_mapping_and_check(uintptr_t badvaddr, int access, istate_t *istate)
-{
-        entry_hi_t hi;
-        pte_t *pte;
-
-        hi.value = cp0_entry_hi_read();
-
-        ASSERT(hi.asid == AS->asid);
-
-        /*
-         * Check if the mapping exists in page tables.
-         */     
-        pte = page_mapping_find(AS, badvaddr, true);
-        if (pte && pte->p && (pte->w || access != PF_ACCESS_WRITE)) {
-                /*
-                 * Mapping found in page tables.
-                 * Immediately succeed.
-                 */
-                return pte;
-        }
-
-        /*
-         * Mapping not found in page tables.
-         * Resort to higher-level page fault handler.
-         */
-        if (as_page_fault(badvaddr, access, istate) == AS_PF_OK) {
-                pte = page_mapping_find(AS, badvaddr, true);
-                ASSERT(pte && pte->p);
-                ASSERT(pte->w || access != PF_ACCESS_WRITE);
-                return pte;
-        }
-
-        return NULL;
+                return;
+        }
+
+        (void) as_page_fault(badvaddr, PF_ACCESS_WRITE, istate);
 }