Large page TLB flush

QEMU uses a fixed page size for the CPU TLB.  If the guest uses large
pages then we effectively split these into multiple smaller pages, and
populate the corresponding TLB entries on demand.

When the guest invalidates the TLB by virtual address we must invalidate
all entries covered by the large page.  However the address used to
invalidate the entry may not be present in the QEMU TLB, so we do not
know which regions to clear.

Implementing a full vaiable size TLB is hard and slow, so just keep a
simple address/mask pair to record which addresses may have been mapped by
large pages.  If the guest invalidates this region then flush the
whole TLB.

Signed-off-by: Paul Brook <paul@codesourcery.com>

1 files changed, 45 insertions, 10 deletions

diff --git a/exec.c b/exec.c
index b0b6056..14767b7 100644
--- a/exec.c
+++ b/exec.c
@@ -1918,6 +1918,8 @@ void tlb_flush(CPUState *env, int flush_global)
 
     memset (env->tb_jmp_cache, 0, TB_JMP_CACHE_SIZE * sizeof (void *));
 
+    env->tlb_flush_addr = -1;
+    env->tlb_flush_mask = 0;
     tlb_flush_count++;
 }
 
@@ -1941,6 +1943,16 @@ void tlb_flush_page(CPUState *env, target_ulong addr)
 #if defined(DEBUG_TLB)
     printf("tlb_flush_page: " TARGET_FMT_lx "\n", addr);
 #endif
+    /* Check if we need to flush due to large pages.  */
+    if ((addr & env->tlb_flush_mask) == env->tlb_flush_addr) {
+#if defined(DEBUG_TLB)
+        printf("tlb_flush_page: forced full flush ("
+               TARGET_FMT_lx "/" TARGET_FMT_lx ")\n",
+               env->tlb_flush_addr, env->tlb_flush_mask);
+#endif
+        tlb_flush(env, 1);
+        return;
+    }
     /* must reset current TB so that interrupts cannot modify the
        links while we are modifying them */
     env->current_tb = NULL;
@@ -2090,13 +2102,35 @@ static inline void tlb_set_dirty(CPUState *env, target_ulong vaddr)
         tlb_set_dirty1(&env->tlb_table[mmu_idx][i], vaddr);
 }
 
-/* add a new TLB entry. At most one entry for a given virtual address
-   is permitted. Return 0 if OK or 2 if the page could not be mapped
-   (can only happen in non SOFTMMU mode for I/O pages or pages
-   conflicting with the host address space). */
-int tlb_set_page_exec(CPUState *env, target_ulong vaddr,
-                      target_phys_addr_t paddr, int prot,
-                      int mmu_idx, int is_softmmu)
+/* Our TLB does not support large pages, so remember the area covered by
+   large pages and trigger a full TLB flush if these are invalidated.  */
+static void tlb_add_large_page(CPUState *env, target_ulong vaddr,
+                               target_ulong size)
+{
+    target_ulong mask = ~(size - 1);
+
+    if (env->tlb_flush_addr == (target_ulong)-1) {
+        env->tlb_flush_addr = vaddr & mask;
+        env->tlb_flush_mask = mask;
+        return;
+    }
+    /* Extend the existing region to include the new page.
+       This is a compromise between unnecessary flushes and the cost
+       of maintaining a full variable size TLB.  */
+    mask &= env->tlb_flush_mask;
+    while (((env->tlb_flush_addr ^ vaddr) & mask) != 0) {
+        mask <<= 1;
+    }
+    env->tlb_flush_addr &= mask;
+    env->tlb_flush_mask = mask;
+}
+
+/* Add a new TLB entry. At most one entry for a given virtual address
+   is permitted. Only a single TARGET_PAGE_SIZE region is mapped, the
+   supplied size is only used by tlb_flush_page.  */
+void tlb_set_page(CPUState *env, target_ulong vaddr,
+                  target_phys_addr_t paddr, int prot,
+                  int mmu_idx, target_ulong size)
 {
     PhysPageDesc *p;
     unsigned long pd;
@@ -2104,11 +2138,14 @@ int tlb_set_page_exec(CPUState *env, target_ulong vaddr,
     target_ulong address;
     target_ulong code_address;
     target_phys_addr_t addend;
-    int ret;
     CPUTLBEntry *te;
     CPUWatchpoint *wp;
     target_phys_addr_t iotlb;
 
+    assert(size >= TARGET_PAGE_SIZE);
+    if (size != TARGET_PAGE_SIZE) {
+        tlb_add_large_page(env, vaddr, size);
+    }
     p = phys_page_find(paddr >> TARGET_PAGE_BITS);
     if (!p) {
         pd = IO_MEM_UNASSIGNED;
@@ -2120,7 +2157,6 @@ int tlb_set_page_exec(CPUState *env, target_ulong vaddr,
            vaddr, (int)paddr, prot, mmu_idx, is_softmmu, pd);
 #endif
 
-    ret = 0;
     address = vaddr;
     if ((pd & ~TARGET_PAGE_MASK) > IO_MEM_ROM && !(pd & IO_MEM_ROMD)) {
         /* IO memory case (romd handled later) */
@@ -2190,7 +2226,6 @@ int tlb_set_page_exec(CPUState *env, target_ulong vaddr,
     } else {
         te->addr_write = -1;
     }
-    return ret;
 }
 
 #else