[Qemu-devel] [RFC 2/5] Add new TLB_EXCL flag

[Alvise Rigo]

Add a new flag for the TLB entries to force all the accesses made to a
page to follow the slow-path.

Mark the accessed page as dirty to invalidate any pending operation of
LL/SC.

Suggested-by: Jani Kokkonen <address@hidden>
Suggested-by: Claudio Fontana <address@hidden>
Signed-off-by: Alvise Rigo <address@hidden>
---
 cputlb.c               |  7 ++++++-
 include/exec/cpu-all.h |  1 +
 softmmu_template.h     | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/cputlb.c b/cputlb.c
index 38f2151..3e4ccba 100644
--- a/cputlb.c
+++ b/cputlb.c
@@ -324,7 +324,12 @@ void tlb_set_page(CPUState *cpu, target_ulong vaddr,
                                                    + xlat)) {
             te->addr_write = address | TLB_NOTDIRTY;
         } else {
-            te->addr_write = address;
+            if (!cpu_physical_memory_excl_is_dirty(section->mr->ram_addr
+                                                   + xlat)) {
+                te->addr_write = address | TLB_EXCL;
+            } else {
+                te->addr_write = address;
+            }
         }
     } else {
         te->addr_write = -1;
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index ac06c67..bd19a94 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -311,6 +311,7 @@ extern RAMList ram_list;
 #define TLB_NOTDIRTY    (1 << 4)
 /* Set if TLB entry is an IO callback.  */
 #define TLB_MMIO        (1 << 5)
+#define TLB_EXCL        (1 << 6)
 
 void dump_exec_info(FILE *f, fprintf_function cpu_fprintf);
 void dump_opcount_info(FILE *f, fprintf_function cpu_fprintf);
diff --git a/softmmu_template.h b/softmmu_template.h
index 0e3dd35..1ac99da 100644
--- a/softmmu_template.h
+++ b/softmmu_template.h
@@ -242,6 +242,7 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, target_ulong 
addr, int mmu_idx,
 #endif
 
     haddr = addr + env->tlb_table[mmu_idx][index].addend;
+
 #if DATA_SIZE == 1
     res = glue(glue(ld, LSUFFIX), _p)((uint8_t *)haddr);
 #else
@@ -262,7 +263,7 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, target_ulong 
addr, int mmu_idx,
     uintptr_t haddr;
     DATA_TYPE res;
 
-    /* Adjust the given return address.  */
+        /* Adjust the given return address.  */
     retaddr -= GETPC_ADJ;
 
     /* If the TLB entry is for a different page, reload and try again.  */
@@ -387,6 +388,7 @@ void helper_le_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
     int index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
     target_ulong tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
     uintptr_t haddr;
+    bool to_excl_mem = false;
 
     /* Adjust the given return address.  */
     retaddr -= GETPC_ADJ;
@@ -406,6 +408,14 @@ void helper_le_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
         tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
     }
 
+    if (unlikely(tlb_addr & TLB_EXCL &&
+        !(tlb_addr & ~(TARGET_PAGE_MASK | TLB_EXCL)))) {
+        /* The slow-path has been forced since we are reading a page used for a
+         * load-link operation. */
+        to_excl_mem = true;
+        goto skip_io;
+    }
+
     /* Handle an IO access.  */
     if (unlikely(tlb_addr & ~TARGET_PAGE_MASK)) {
         hwaddr ioaddr;
@@ -445,6 +455,7 @@ void helper_le_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
         return;
     }
 
+skip_io:
     /* Handle aligned access or unaligned access in the same page.  */
 #ifdef ALIGNED_ONLY
     if ((addr & (DATA_SIZE - 1)) != 0) {
@@ -453,6 +464,17 @@ void helper_le_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
     }
 #endif
 
+    /* If we are performing a store to exclusive-protected memory,
+     * set the bit to dirty. */
+    if (unlikely(to_excl_mem)) {
+        MemoryRegionSection *section;
+        hwaddr xlat, sz;
+
+        section = address_space_translate_for_iotlb(ENV_GET_CPU(env), tlb_addr,
+                                                    &xlat, &sz);
+        cpu_physical_memory_set_excl_dirty(section->mr->ram_addr + xlat);
+    }
+
     haddr = addr + env->tlb_table[mmu_idx][index].addend;
 #if DATA_SIZE == 1
     glue(glue(st, SUFFIX), _p)((uint8_t *)haddr, val);
@@ -468,6 +490,14 @@ void helper_be_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
     int index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
     target_ulong tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
     uintptr_t haddr;
+    bool to_excl_mem = false;
+
+    if (unlikely(tlb_addr & TLB_EXCL &&
+            !(tlb_addr & ~(TARGET_PAGE_MASK | TLB_EXCL)))) {
+        /* The slow-path has been forced since we are reading a page used for a
+         * load-link operation. */
+        to_excl_mem = true;
+    }
 
     /* Adjust the given return address.  */
     retaddr -= GETPC_ADJ;
@@ -487,6 +517,10 @@ void helper_be_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
         tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
     }
 
+    if (to_excl_mem) {
+        goto skip_io;
+    }
+
     /* Handle an IO access.  */
     if (unlikely(tlb_addr & ~TARGET_PAGE_MASK)) {
         hwaddr ioaddr;
@@ -526,6 +560,7 @@ void helper_be_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
         return;
     }
 
+skip_io:
     /* Handle aligned access or unaligned access in the same page.  */
 #ifdef ALIGNED_ONLY
     if ((addr & (DATA_SIZE - 1)) != 0) {
@@ -534,6 +569,17 @@ void helper_be_st_name(CPUArchState *env, target_ulong 
addr, DATA_TYPE val,
     }
 #endif
 
+    /* If we are performing a store to exclusive-protected memory,
+     * set the bit to dirty. */
+    if (unlikely(to_excl_mem)) {
+        MemoryRegionSection *section;
+        hwaddr xlat, sz;
+
+        section = address_space_translate_for_iotlb(ENV_GET_CPU(env), tlb_addr,
+                                                    &xlat, &sz);
+        cpu_physical_memory_set_excl_dirty(section->mr->ram_addr + xlat);
+    }
+
     haddr = addr + env->tlb_table[mmu_idx][index].addend;
     glue(glue(st, SUFFIX), _be_p)((uint8_t *)haddr, val);
 }
-- 
2.4.0