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, 7 insertions, 107 deletions

diff --git a/exec.c b/exec.c
index 8575ce5..ad0f4a5 100644
--- a/exec.c
+++ b/exec.c
@@ -193,15 +193,12 @@ typedef struct subpage_t {
 #define PHYS_SECTION_UNASSIGNED 0
 #define PHYS_SECTION_NOTDIRTY 1
 #define PHYS_SECTION_ROM 2
-#define PHYS_SECTION_WATCH 3
 
 static void io_mem_init(void);
 static void memory_map_init(void);
 static void tcg_log_global_after_sync(MemoryListener *listener);
 static void tcg_commit(MemoryListener *listener);
 
-static MemoryRegion io_mem_watch;
-
 /**
  * CPUAddressSpace: all the information a CPU needs about an AddressSpace
  * @cpu: the CPU whose AddressSpace this is
@@ -1472,7 +1469,6 @@ hwaddr memory_region_section_get_iotlb(CPUState *cpu,
                                        target_ulong *address)
 {
     hwaddr iotlb;
-    int flags, match;
 
     if (memory_region_is_ram(section->mr)) {
         /* Normal RAM.  */
@@ -1490,19 +1486,6 @@ hwaddr memory_region_section_get_iotlb(CPUState *cpu,
         iotlb += xlat;
     }
 
-    /* Avoid trapping reads of pages with a write breakpoint. */
-    match = (prot & PAGE_READ ? BP_MEM_READ : 0)
-          | (prot & PAGE_WRITE ? BP_MEM_WRITE : 0);
-    flags = cpu_watchpoint_address_matches(cpu, vaddr, TARGET_PAGE_SIZE);
-    if (flags & match) {
-        /*
-         * Make accesses to pages with watchpoints go via the
-         * watchpoint trap routines.
-         */
-        iotlb = PHYS_SECTION_WATCH + paddr;
-        *address |= TLB_MMIO;
-    }
-
     return iotlb;
 }
 #endif /* defined(CONFIG_USER_ONLY) */
@@ -2810,10 +2793,14 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
 
     assert(tcg_enabled());
     if (cpu->watchpoint_hit) {
-        /* We re-entered the check after replacing the TB. Now raise
-         * the debug interrupt so that is will trigger after the
-         * current instruction. */
+        /*
+         * We re-entered the check after replacing the TB.
+         * Now raise the debug interrupt so that it will
+         * trigger after the current instruction.
+         */
+        qemu_mutex_lock_iothread();
         cpu_interrupt(cpu, CPU_INTERRUPT_DEBUG);
+        qemu_mutex_unlock_iothread();
         return;
     }
 
@@ -2858,88 +2845,6 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
     }
 }
 
-static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags)
-{
-    CPUState *cpu = current_cpu;
-    vaddr addr = (cpu->mem_io_vaddr & TARGET_PAGE_MASK) + offset;
-
-    cpu_check_watchpoint(cpu, addr, len, attrs, flags, 0);
-}
-
-/* Watchpoint access routines.  Watchpoints are inserted using TLB tricks,
-   so these check for a hit then pass through to the normal out-of-line
-   phys routines.  */
-static MemTxResult watch_mem_read(void *opaque, hwaddr addr, uint64_t *pdata,
-                                  unsigned size, MemTxAttrs attrs)
-{
-    MemTxResult res;
-    uint64_t data;
-    int asidx = cpu_asidx_from_attrs(current_cpu, attrs);
-    AddressSpace *as = current_cpu->cpu_ases[asidx].as;
-
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, size, attrs, BP_MEM_READ);
-    switch (size) {
-    case 1:
-        data = address_space_ldub(as, addr, attrs, &res);
-        break;
-    case 2:
-        data = address_space_lduw(as, addr, attrs, &res);
-        break;
-    case 4:
-        data = address_space_ldl(as, addr, attrs, &res);
-        break;
-    case 8:
-        data = address_space_ldq(as, addr, attrs, &res);
-        break;
-    default: abort();
-    }
-    *pdata = data;
-    return res;
-}
-
-static MemTxResult watch_mem_write(void *opaque, hwaddr addr,
-                                   uint64_t val, unsigned size,
-                                   MemTxAttrs attrs)
-{
-    MemTxResult res;
-    int asidx = cpu_asidx_from_attrs(current_cpu, attrs);
-    AddressSpace *as = current_cpu->cpu_ases[asidx].as;
-
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, size, attrs, BP_MEM_WRITE);
-    switch (size) {
-    case 1:
-        address_space_stb(as, addr, val, attrs, &res);
-        break;
-    case 2:
-        address_space_stw(as, addr, val, attrs, &res);
-        break;
-    case 4:
-        address_space_stl(as, addr, val, attrs, &res);
-        break;
-    case 8:
-        address_space_stq(as, addr, val, attrs, &res);
-        break;
-    default: abort();
-    }
-    return res;
-}
-
-static const MemoryRegionOps watch_mem_ops = {
-    .read_with_attrs = watch_mem_read,
-    .write_with_attrs = watch_mem_write,
-    .endianness = DEVICE_NATIVE_ENDIAN,
-    .valid = {
-        .min_access_size = 1,
-        .max_access_size = 8,
-        .unaligned = false,
-    },
-    .impl = {
-        .min_access_size = 1,
-        .max_access_size = 8,
-        .unaligned = false,
-    },
-};
-
 static MemTxResult flatview_read(FlatView *fv, hwaddr addr,
                                  MemTxAttrs attrs, uint8_t *buf, hwaddr len);
 static MemTxResult flatview_write(FlatView *fv, hwaddr addr, MemTxAttrs attrs,
@@ -3115,9 +3020,6 @@ static void io_mem_init(void)
     memory_region_init_io(&io_mem_notdirty, NULL, &notdirty_mem_ops, NULL,
                           NULL, UINT64_MAX);
     memory_region_clear_global_locking(&io_mem_notdirty);
-
-    memory_region_init_io(&io_mem_watch, NULL, &watch_mem_ops, NULL,
-                          NULL, UINT64_MAX);
 }
 
 AddressSpaceDispatch *address_space_dispatch_new(FlatView *fv)
@@ -3131,8 +3033,6 @@ AddressSpaceDispatch *address_space_dispatch_new(FlatView *fv)
     assert(n == PHYS_SECTION_NOTDIRTY);
     n = dummy_section(&d->map, fv, &io_mem_rom);
     assert(n == PHYS_SECTION_ROM);
-    n = dummy_section(&d->map, fv, &io_mem_watch);
-    assert(n == PHYS_SECTION_WATCH);
 
     d->phys_map  = (PhysPageEntry) { .ptr = PHYS_MAP_NODE_NIL, .skip = 1 };