tcg: Remove TCG_OVERSIZED_GUEST

This is now prohibited in configuration.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/cputlb.c

@@ -47,7 +47,6 @@
 #include "qemu/plugin-memory.h"
 #endif
 #include "tcg/tcg-ldst.h"
-#include "tcg/oversized-guest.h"
 
 /* DEBUG defines, enable DEBUG_TLB_LOG to log to the CPU_LOG_MMU target */
 /* #define DEBUG_TLB */
@@ -118,12 +117,8 @@ static inline uint64_t tlb_read_idx(const CPUTLBEntry *entry,
     return qatomic_read(ptr);
 #else
     const uint64_t *ptr = &entry->addr_idx[access_type];
-# if TCG_OVERSIZED_GUEST
-    return *ptr;
-# else
     /* ofs might correspond to .addr_write, so use qatomic_read */
     return qatomic_read(ptr);
-# endif
 #endif
 }
 
@@ -908,8 +903,6 @@ static void tlb_reset_dirty_range_locked(CPUTLBEntry *tlb_entry,
             uint32_t *ptr_write = (uint32_t *)&tlb_entry->addr_write;
             ptr_write += HOST_BIG_ENDIAN;
             qatomic_set(ptr_write, *ptr_write | TLB_NOTDIRTY);
-#elif TCG_OVERSIZED_GUEST
-            tlb_entry->addr_write |= TLB_NOTDIRTY;
 #else
             qatomic_set(&tlb_entry->addr_write,
                         tlb_entry->addr_write | TLB_NOTDIRTY);

accel/tcg/tcg-all.c

@@ -28,7 +28,6 @@
 #include "exec/replay-core.h"
 #include "system/cpu-timers.h"
 #include "tcg/startup.h"
-#include "tcg/oversized-guest.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "qemu/accel.h"
@@ -41,6 +40,8 @@
 #include "hw/boards.h"
 #endif
 #include "internal-common.h"
+#include "cpu-param.h"
+
 
 struct TCGState {
     AccelState parent_obj;
@@ -72,7 +73,7 @@ DECLARE_INSTANCE_CHECKER(TCGState, TCG_STATE,
 
 static bool default_mttcg_enabled(void)
 {
-    if (icount_enabled() || TCG_OVERSIZED_GUEST) {
+    if (icount_enabled()) {
         return false;
     }
 #ifdef TARGET_SUPPORTS_MTTCG
@@ -145,9 +146,7 @@ static void tcg_set_thread(Object *obj, const char *value, Error **errp)
     TCGState *s = TCG_STATE(obj);
 
     if (strcmp(value, "multi") == 0) {
-        if (TCG_OVERSIZED_GUEST) {
-            error_setg(errp, "No MTTCG when guest word size > hosts");
-        } else if (icount_enabled()) {
+        if (icount_enabled()) {
             error_setg(errp, "No MTTCG when icount is enabled");
         } else {
 #ifndef TARGET_SUPPORTS_MTTCG

docs/devel/multi-thread-tcg.rst

@@ -37,7 +37,6 @@ if:
 
 * forced by --accel tcg,thread=single
 * enabling --icount mode
-* 64 bit guests on 32 bit hosts (TCG_OVERSIZED_GUEST)
 
 In the general case of running translated code there should be no
 inter-vCPU dependencies and all vCPUs should be able to run at full

include/qemu/atomic.h

@@ -56,25 +56,13 @@
  */
 #define signal_barrier()    __atomic_signal_fence(__ATOMIC_SEQ_CST)
 
-/* Sanity check that the size of an atomic operation isn't "overly large".
+/*
+ * Sanity check that the size of an atomic operation isn't "overly large".
  * Despite the fact that e.g. i686 has 64-bit atomic operations, we do not
  * want to use them because we ought not need them, and this lets us do a
  * bit of sanity checking that other 32-bit hosts might build.
- *
- * That said, we have a problem on 64-bit ILP32 hosts in that in order to
- * sync with TCG_OVERSIZED_GUEST, this must match TCG_TARGET_REG_BITS.
- * We'd prefer not want to pull in everything else TCG related, so handle
- * those few cases by hand.
- *
- * Note that x32 is fully detected with __x86_64__ + _ILP32, and that for
- * Sparc we always force the use of sparcv9 in configure. MIPS n32 (ILP32) &
- * n64 (LP64) ABIs are both detected using __mips64.
  */
-#if defined(__x86_64__) || defined(__sparc__) || defined(__mips64)
-# define ATOMIC_REG_SIZE  8
-#else
-# define ATOMIC_REG_SIZE  sizeof(void *)
-#endif
+#define ATOMIC_REG_SIZE  sizeof(void *)
 
 /* Weak atomic operations prevent the compiler moving other
  * loads/stores past the atomic operation load/store. However there is

include/tcg/oversized-guest.h

@@ -1,23 +0,0 @@
-/* SPDX-License-Identifier: MIT */
-/*
- * Define TCG_OVERSIZED_GUEST
- * Copyright (c) 2008 Fabrice Bellard
- */
-
-#ifndef EXEC_TCG_OVERSIZED_GUEST_H
-#define EXEC_TCG_OVERSIZED_GUEST_H
-
-#include "tcg-target-reg-bits.h"
-#include "cpu-param.h"
-
-/*
- * Oversized TCG guests make things like MTTCG hard
- * as we can't use atomics for cputlb updates.
- */
-#if TARGET_LONG_BITS > TCG_TARGET_REG_BITS
-#define TCG_OVERSIZED_GUEST 1
-#else
-#define TCG_OVERSIZED_GUEST 0
-#endif
-
-#endif

target/arm/ptw.c

@@ -16,9 +16,6 @@
 #include "internals.h"
 #include "cpu-features.h"
 #include "idau.h"
-#ifdef CONFIG_TCG
-# include "tcg/oversized-guest.h"
-#endif
 
 typedef struct S1Translate {
     /*
@@ -840,7 +837,6 @@ static uint64_t arm_casq_ptw(CPUARMState *env, uint64_t old_val,
         ptw->out_rw = true;
     }
 
-#ifdef CONFIG_ATOMIC64
     if (ptw->out_be) {
         old_val = cpu_to_be64(old_val);
         new_val = cpu_to_be64(new_val);
@@ -852,36 +848,6 @@ static uint64_t arm_casq_ptw(CPUARMState *env, uint64_t old_val,
         cur_val = qatomic_cmpxchg__nocheck((uint64_t *)host, old_val, new_val);
         cur_val = le64_to_cpu(cur_val);
     }
-#else
-    /*
-     * We can't support the full 64-bit atomic cmpxchg on the host.
-     * Because this is only used for FEAT_HAFDBS, which is only for AA64,
-     * we know that TCG_OVERSIZED_GUEST is set, which means that we are
-     * running in round-robin mode and could only race with dma i/o.
-     */
-#if !TCG_OVERSIZED_GUEST
-# error "Unexpected configuration"
-#endif
-    bool locked = bql_locked();
-    if (!locked) {
-        bql_lock();
-    }
-    if (ptw->out_be) {
-        cur_val = ldq_be_p(host);
-        if (cur_val == old_val) {
-            stq_be_p(host, new_val);
-        }
-    } else {
-        cur_val = ldq_le_p(host);
-        if (cur_val == old_val) {
-            stq_le_p(host, new_val);
-        }
-    }
-    if (!locked) {
-        bql_unlock();
-    }
-#endif
-
     return cur_val;
 #else
     /* AArch32 does not have FEAT_HADFS; non-TCG guests only use debug-mode. */

target/riscv/cpu_helper.c

@@ -32,7 +32,6 @@
 #include "system/cpu-timers.h"
 #include "cpu_bits.h"
 #include "debug.h"
-#include "tcg/oversized-guest.h"
 #include "pmp.h"
 
 int riscv_env_mmu_index(CPURISCVState *env, bool ifetch)
@@ -1167,9 +1166,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
     hwaddr pte_addr;
     int i;
 
-#if !TCG_OVERSIZED_GUEST
-restart:
-#endif
+ restart:
     for (i = 0; i < levels; i++, ptshift -= ptidxbits) {
         target_ulong idx;
         if (i == 0) {
@@ -1388,13 +1385,6 @@ restart:
                                      false, MEMTXATTRS_UNSPECIFIED);
         if (memory_region_is_ram(mr)) {
             target_ulong *pte_pa = qemu_map_ram_ptr(mr->ram_block, addr1);
-#if TCG_OVERSIZED_GUEST
-            /*
-             * MTTCG is not enabled on oversized TCG guests so
-             * page table updates do not need to be atomic
-             */
-            *pte_pa = pte = updated_pte;
-#else
             target_ulong old_pte;
             if (riscv_cpu_sxl(env) == MXL_RV32) {
                 old_pte = qatomic_cmpxchg((uint32_t *)pte_pa, pte, updated_pte);
@@ -1405,7 +1395,6 @@ restart:
                 goto restart;
             }
             pte = updated_pte;
-#endif
         } else {
             /*
              * Misconfigured PTE in ROM (AD bits are not preset) or