[Qemu-devel] [PATCH v1 6/6] mem: change tcg code to rcu style

[Liu Ping Fan <qemulist@gmail.com>]

From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>

When adopting rcu style, for tcg code, need to fix two kind of path:
 -tlb_set_page() will cache translation info.
 -instruction emualation path

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
----
Not sure about tcg code, so I took helper_st as the example.
---
 cputlb.c                        |   25 +++++++++++++++++-
 exec.c                          |    2 +-
 include/exec/softmmu_template.h |   53 +++++++++++++++++++++++++++++++-------
 3 files changed, 68 insertions(+), 12 deletions(-)

diff --git a/cputlb.c b/cputlb.c
index 86666c8..6b55c70 100644
--- a/cputlb.c
+++ b/cputlb.c
@@ -249,6 +249,10 @@ void tlb_set_page(CPUArchState *env, target_ulong vaddr,
     uintptr_t addend;
     CPUTLBEntry *te;
     hwaddr iotlb, xlat, sz;
+    unsigned long start;
+    Node *map_base;
+    MemoryRegionSection *sections_base;
+    PhysPageEntry *roots_base;
 
     assert(size >= TARGET_PAGE_SIZE);
     if (size != TARGET_PAGE_SIZE) {
@@ -256,8 +260,18 @@ void tlb_set_page(CPUArchState *env, target_ulong vaddr,
     }
 
     sz = size;
+
+reload:
+    rcu_read_lock();
+    start = seqlock_read_begin(&dispatch_table_lock);
+    map_base = cur_map_nodes;
+    sections_base = cur_phys_sections;
+    roots_base = cur_roots;
     section = address_space_translate(&address_space_memory, paddr, &xlat, &sz,
-                                      false);
+                                      false,
+                                      map_base,
+                                      sections_base,
+                                      roots_base);
     assert(sz >= TARGET_PAGE_SIZE);
 
 #if defined(DEBUG_TLB)
@@ -282,6 +296,9 @@ void tlb_set_page(CPUArchState *env, target_ulong vaddr,
 
     index = (vaddr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
     env->iotlb[mmu_idx][index] = iotlb - vaddr;
+    /* Serialized with reader, so only need to worry about tlb_flush
+      * in parellel.  If there is conflict, just reload tlb entry until right.
+      */
     te = &env->tlb_table[mmu_idx][index];
     te->addend = addend - vaddr;
     if (prot & PAGE_READ) {
@@ -309,6 +326,12 @@ void tlb_set_page(CPUArchState *env, target_ulong vaddr,
     } else {
         te->addr_write = -1;
     }
+
+    if (unlikely(seqlock_read_check(&dispatch_table_lock, start))) {
+        rcu_read_unlock();
+        goto reload;
+    }
+    rcu_read_unlock();
 }
 
 /* NOTE: this function can trigger an exception */
diff --git a/exec.c b/exec.c
index 9a5c67f..d4ca101 100644
--- a/exec.c
+++ b/exec.c
@@ -1820,7 +1820,6 @@ static void core_commit(MemoryListener *listener)
     cur_phys_sections = next_phys_sections;
     cur_alloc_info = next_alloc_info;
     cur_roots = next_roots;
-    seqlock_write_unlock(&dispatch_table_lock);
 
     /* since each CPU stores ram addresses in its TLB cache, we must
        reset the modified entries */
@@ -1828,6 +1827,7 @@ static void core_commit(MemoryListener *listener)
     for (env = first_cpu; env != NULL; env = env->next_cpu) {
         tlb_flush(env, 1);
     }
+    seqlock_write_unlock(&dispatch_table_lock);
 
     /* Fix me, will changed to call_rcu */
     release_dispatch_map(info);
diff --git a/include/exec/softmmu_template.h b/include/exec/softmmu_template.h
index 8584902..7fa631e 100644
--- a/include/exec/softmmu_template.h
+++ b/include/exec/softmmu_template.h
@@ -196,13 +196,16 @@ static void glue(glue(slow_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
                                                    int mmu_idx,
                                                    uintptr_t retaddr);
 
+/* Caller hold rcu read lock, this func will release lock */
 static inline void glue(io_write, SUFFIX)(CPUArchState *env,
                                           hwaddr physaddr,
                                           DATA_TYPE val,
                                           target_ulong addr,
-                                          uintptr_t retaddr)
+                                          uintptr_t retaddr,
+                                          MemoryRegionSection *mrs_base)
 {
-    MemoryRegion *mr = iotlb_to_region(physaddr);
+    subpage_t *subpg;
+    MemoryRegion *mr = mrs_base[[physaddr & ~TARGET_PAGE_MASK].mr;
 
     physaddr = (physaddr & TARGET_PAGE_MASK) + addr;
     if (mr != &io_mem_rom && mr != &io_mem_notdirty && !can_do_io(env)) {
@@ -211,6 +214,13 @@ static inline void glue(io_write, SUFFIX)(CPUArchState *env,
 
     env->mem_io_vaddr = addr;
     env->mem_io_pc = retaddr;
+    if (!mr->terminates) {
+        subpg = container_of(mr, subpage_t, mmio);
+        idx = SUBPAGE_IDX(addr);
+        mr = mrs_base[subpg->sections[idx]].mr;
+    }
+    memory_region_ref(mr);
+    rcu_read_unlock();
     io_mem_write(mr, physaddr, val, 1 << SHIFT);
 }
 
@@ -222,17 +232,28 @@ void glue(glue(helper_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
     target_ulong tlb_addr;
     uintptr_t retaddr;
     int index;
+    unsigned int start;
+    MemoryRegionSection *mrs_base;
+    uintptr_t addend;
 
     index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
  redo:
-    tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
+    rcu_read_lock();
+    do {
+        start = seqlock_read_begin(&dispatch_table_lock);
+        tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
+        ioaddr = env->iotlb[mmu_idx][index];
+        addend = env->tlb_table[mmu_idx][index].addend;
+        mrs_base =  cur_phys_sections;
+    } while (seqlock_read_check(&dispatch_table_lock, start));
+
     if ((addr & TARGET_PAGE_MASK) == (tlb_addr & (TARGET_PAGE_MASK | TLB_INVALID_MASK))) {
         if (tlb_addr & ~TARGET_PAGE_MASK) {
             /* IO access */
             if ((addr & (DATA_SIZE - 1)) != 0)
                 goto do_unaligned_access;
             retaddr = GETPC_EXT();
-            ioaddr = env->iotlb[mmu_idx][index];
+            /* will rcu_read_unlock() inside */
             glue(io_write, SUFFIX)(env, ioaddr, val, addr, retaddr);
         } else if (((addr & ~TARGET_PAGE_MASK) + DATA_SIZE - 1) >= TARGET_PAGE_SIZE) {
         do_unaligned_access:
@@ -240,22 +261,23 @@ void glue(glue(helper_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
 #ifdef ALIGNED_ONLY
             do_unaligned_access(env, addr, 1, mmu_idx, retaddr);
 #endif
+            rcu_read_unlock();
             glue(glue(slow_st, SUFFIX), MMUSUFFIX)(env, addr, val,
                                                    mmu_idx, retaddr);
         } else {
             /* aligned/unaligned access in the same page */
-            uintptr_t addend;
 #ifdef ALIGNED_ONLY
             if ((addr & (DATA_SIZE - 1)) != 0) {
                 retaddr = GETPC_EXT();
                 do_unaligned_access(env, addr, 1, mmu_idx, retaddr);
             }
 #endif
-            addend = env->tlb_table[mmu_idx][index].addend;
             glue(glue(st, SUFFIX), _raw)((uint8_t *)(intptr_t)
                                          (addr + addend), val);
+            rcu_read_unlock();
         }
     } else {
+        rcu_read_unlock();
         /* the page is not in the TLB : fill it */
         retaddr = GETPC_EXT();
 #ifdef ALIGNED_ONLY
@@ -277,17 +299,25 @@ static void glue(glue(slow_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
     hwaddr ioaddr;
     target_ulong tlb_addr;
     int index, i;
+    uintptr_t addend;
 
     index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
  redo:
-    tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
+    rcu_read_lock();
+    do {
+        start = seqlock_read_begin(&dispatch_table_lock);
+        tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
+        ioaddr = env->iotlb[mmu_idx][index];
+        addend = env->tlb_table[mmu_idx][index].addend;
+        mrs_base =  cur_phys_sections;
+    } while (seqlock_read_check(&dispatch_table_lock, start));
+
     if ((addr & TARGET_PAGE_MASK) == (tlb_addr & (TARGET_PAGE_MASK | TLB_INVALID_MASK))) {
         if (tlb_addr & ~TARGET_PAGE_MASK) {
             /* IO access */
             if ((addr & (DATA_SIZE - 1)) != 0)
                 goto do_unaligned_access;
-            ioaddr = env->iotlb[mmu_idx][index];
-            glue(io_write, SUFFIX)(env, ioaddr, val, addr, retaddr);
+            glue(io_write, SUFFIX)(env, ioaddr, val, addr, retaddr, mrs_base);
         } else if (((addr & ~TARGET_PAGE_MASK) + DATA_SIZE - 1) >= TARGET_PAGE_SIZE) {
         do_unaligned_access:
             /* XXX: not efficient, but simple */
@@ -295,10 +325,12 @@ static void glue(glue(slow_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
              * previous page from the TLB cache.  */
             for(i = DATA_SIZE - 1; i >= 0; i--) {
 #ifdef TARGET_WORDS_BIGENDIAN
+                rcu_read_unlock();
                 glue(slow_stb, MMUSUFFIX)(env, addr + i,
                                           val >> (((DATA_SIZE - 1) * 8) - (i * 8)),
                                           mmu_idx, retaddr);
 #else
+                rcu_read_unlock();
                 glue(slow_stb, MMUSUFFIX)(env, addr + i,
                                           val >> (i * 8),
                                           mmu_idx, retaddr);
@@ -306,11 +338,12 @@ static void glue(glue(slow_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
             }
         } else {
             /* aligned/unaligned access in the same page */
-            uintptr_t addend = env->tlb_table[mmu_idx][index].addend;
             glue(glue(st, SUFFIX), _raw)((uint8_t *)(intptr_t)
                                          (addr + addend), val);
+            rcu_read_unlock();
         }
     } else {
+        rcu_read_unlock();
         /* the page is not in the TLB : fill it */
         tlb_fill(env, addr, 1, mmu_idx, retaddr);
         goto redo;
-- 
1.7.4.4