cputlb: Handle watchpoints via TLB_WATCHPOINT

The raising of exceptions from check_watchpoint, buried inside
of the I/O subsystem, is fundamentally broken.  We do not have
the helper return address with which we can unwind guest state.

Replace PHYS_SECTION_WATCH and io_mem_watch with TLB_WATCHPOINT.
Move the call to cpu_check_watchpoint into the cputlb helpers
where we do have the helper return address.

This allows watchpoints on RAM to bypass the full i/o access path.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 79 insertions, 10 deletions

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index d0f8db3..9a9a626 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -710,6 +710,7 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
     hwaddr iotlb, xlat, sz, paddr_page;
     target_ulong vaddr_page;
     int asidx = cpu_asidx_from_attrs(cpu, attrs);
+    int wp_flags;
 
     assert_cpu_is_self(cpu);
 
@@ -752,6 +753,8 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
     code_address = address;
     iotlb = memory_region_section_get_iotlb(cpu, section, vaddr_page,
                                             paddr_page, xlat, prot, &address);
+    wp_flags = cpu_watchpoint_address_matches(cpu, vaddr_page,
+                                              TARGET_PAGE_SIZE);
 
     index = tlb_index(env, mmu_idx, vaddr_page);
     te = tlb_entry(env, mmu_idx, vaddr_page);
@@ -805,6 +808,9 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
     tn.addend = addend - vaddr_page;
     if (prot & PAGE_READ) {
         tn.addr_read = address;
+        if (wp_flags & BP_MEM_READ) {
+            tn.addr_read |= TLB_WATCHPOINT;
+        }
     } else {
         tn.addr_read = -1;
     }
@@ -831,6 +837,9 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
         if (prot & PAGE_WRITE_INV) {
             tn.addr_write |= TLB_INVALID_MASK;
         }
+        if (wp_flags & BP_MEM_WRITE) {
+            tn.addr_write |= TLB_WATCHPOINT;
+        }
     }
 
     copy_tlb_helper_locked(te, &tn);
@@ -1264,13 +1273,33 @@ load_helper(CPUArchState *env, target_ulong addr, TCGMemOpIdx oi,
         tlb_addr &= ~TLB_INVALID_MASK;
     }
 
-    /* Handle an IO access.  */
+    /* Handle anything that isn't just a straight memory access.  */
     if (unlikely(tlb_addr & ~TARGET_PAGE_MASK)) {
+        CPUIOTLBEntry *iotlbentry;
+
+        /* For anything that is unaligned, recurse through full_load.  */
         if ((addr & (size - 1)) != 0) {
             goto do_unaligned_access;
         }
-        return io_readx(env, &env_tlb(env)->d[mmu_idx].iotlb[index],
-                        mmu_idx, addr, retaddr, access_type, op);
+
+        iotlbentry = &env_tlb(env)->d[mmu_idx].iotlb[index];
+
+        /* Handle watchpoints.  */
+        if (unlikely(tlb_addr & TLB_WATCHPOINT)) {
+            /* On watchpoint hit, this will longjmp out.  */
+            cpu_check_watchpoint(env_cpu(env), addr, size,
+                                 iotlbentry->attrs, BP_MEM_READ, retaddr);
+
+            /* The backing page may or may not require I/O.  */
+            tlb_addr &= ~TLB_WATCHPOINT;
+            if ((tlb_addr & ~TARGET_PAGE_MASK) == 0) {
+                goto do_aligned_access;
+            }
+        }
+
+        /* Handle I/O access.  */
+        return io_readx(env, iotlbentry, mmu_idx, addr,
+                        retaddr, access_type, op);
     }
 
     /* Handle slow unaligned access (it spans two pages or IO).  */
@@ -1297,6 +1326,7 @@ load_helper(CPUArchState *env, target_ulong addr, TCGMemOpIdx oi,
         return res & MAKE_64BIT_MASK(0, size * 8);
     }
 
+ do_aligned_access:
     haddr = (void *)((uintptr_t)addr + entry->addend);
     switch (op) {
     case MO_UB:
@@ -1486,13 +1516,32 @@ store_helper(CPUArchState *env, target_ulong addr, uint64_t val,
         tlb_addr = tlb_addr_write(entry) & ~TLB_INVALID_MASK;
     }
 
-    /* Handle an IO access.  */
+    /* Handle anything that isn't just a straight memory access.  */
     if (unlikely(tlb_addr & ~TARGET_PAGE_MASK)) {
+        CPUIOTLBEntry *iotlbentry;
+
+        /* For anything that is unaligned, recurse through byte stores.  */
         if ((addr & (size - 1)) != 0) {
             goto do_unaligned_access;
         }
-        io_writex(env, &env_tlb(env)->d[mmu_idx].iotlb[index], mmu_idx,
-                  val, addr, retaddr, op);
+
+        iotlbentry = &env_tlb(env)->d[mmu_idx].iotlb[index];
+
+        /* Handle watchpoints.  */
+        if (unlikely(tlb_addr & TLB_WATCHPOINT)) {
+            /* On watchpoint hit, this will longjmp out.  */
+            cpu_check_watchpoint(env_cpu(env), addr, size,
+                                 iotlbentry->attrs, BP_MEM_WRITE, retaddr);
+
+            /* The backing page may or may not require I/O.  */
+            tlb_addr &= ~TLB_WATCHPOINT;
+            if ((tlb_addr & ~TARGET_PAGE_MASK) == 0) {
+                goto do_aligned_access;
+            }
+        }
+
+        /* Handle I/O access.  */
+        io_writex(env, iotlbentry, mmu_idx, val, addr, retaddr, op);
         return;
     }
 
@@ -1517,10 +1566,29 @@ store_helper(CPUArchState *env, target_ulong addr, uint64_t val,
         index2 = tlb_index(env, mmu_idx, page2);
         entry2 = tlb_entry(env, mmu_idx, page2);
         tlb_addr2 = tlb_addr_write(entry2);
-        if (!tlb_hit_page(tlb_addr2, page2)
-            && !victim_tlb_hit(env, mmu_idx, index2, tlb_off, page2)) {
-            tlb_fill(env_cpu(env), page2, size2, MMU_DATA_STORE,
-                     mmu_idx, retaddr);
+        if (!tlb_hit_page(tlb_addr2, page2)) {
+            if (!victim_tlb_hit(env, mmu_idx, index2, tlb_off, page2)) {
+                tlb_fill(env_cpu(env), page2, size2, MMU_DATA_STORE,
+                         mmu_idx, retaddr);
+                index2 = tlb_index(env, mmu_idx, page2);
+                entry2 = tlb_entry(env, mmu_idx, page2);
+            }
+            tlb_addr2 = tlb_addr_write(entry2);
+        }
+
+        /*
+         * Handle watchpoints.  Since this may trap, all checks
+         * must happen before any store.
+         */
+        if (unlikely(tlb_addr & TLB_WATCHPOINT)) {
+            cpu_check_watchpoint(env_cpu(env), addr, size - size2,
+                                 env_tlb(env)->d[mmu_idx].iotlb[index].attrs,
+                                 BP_MEM_WRITE, retaddr);
+        }
+        if (unlikely(tlb_addr2 & TLB_WATCHPOINT)) {
+            cpu_check_watchpoint(env_cpu(env), page2, size2,
+                                 env_tlb(env)->d[mmu_idx].iotlb[index2].attrs,
+                                 BP_MEM_WRITE, retaddr);
         }
 
         /*
@@ -1542,6 +1610,7 @@ store_helper(CPUArchState *env, target_ulong addr, uint64_t val,
         return;
     }
 
+ do_aligned_access:
     haddr = (void *)((uintptr_t)addr + entry->addend);
     switch (op) {
     case MO_UB: