[PATCH 1/8] plugins: force slow path when plugins instrument memory ops

["Alex Bennée" <alex.bennee@linaro.org>]

The lack of SVE memory instrumentation has been an omission in plugin
handling since it was introduced. Fortunately we can utilise the
probe_* functions to force all all memory access to follow the slow
path. We do this by checking the access type and presence of plugin
memory callbacks and if set return the TLB_MMIO flag.

We have to jump through a few hoops in user mode to re-use the flag
but it was the desired effect:

 ./qemu-system-aarch64 -display none -serial mon:stdio \
   -M virt -cpu max -semihosting-config enable=on \
   -kernel ./tests/tcg/aarch64-softmmu/memory-sve \
   -plugin ./contrib/plugins/libexeclog.so,ifilter=st1w,afilter=0x40001808 -d plugin

gives (disas doesn't currently understand st1w):

  0, 0x40001808, 0xe54342a0, ".byte 0xa0, 0x42, 0x43, 0xe5", store, 0x40213010, RAM, store, 0x40213014, RAM, store, 0x40213018, RAM

And for user-mode:

  ./qemu-aarch64 \
    -plugin contrib/plugins/libexeclog.so,afilter=0x4007c0 \
    -d plugin \
    ./tests/tcg/aarch64-linux-user/sha512-sve

gives:

  1..10
  ok 1 - do_test(&tests[i])
  0, 0x4007c0, 0xa4004b80, ".byte 0x80, 0x4b, 0x00, 0xa4", load, 0x5500800370, load, 0x5500800371, load, 0x5500800372, load, 0x5500800373, load, 0x5500800374, load, 0x5500800375, load, 0x5500800376, load, 0x5500800377, load, 0x5500800378, load, 0x5500800379, load, 0x550080037a, load, 0x550080037b, load, 0x550080037c, load, 0x550080037d, load, 0x550080037e, load, 0x550080037f, load, 0x5500800380, load, 0x5500800381, load, 0x5500800382, load, 0x5500800383, load, 0x5500800384, load, 0x5500800385, load, 0x5500800386, lo
  ad, 0x5500800387, load, 0x5500800388, load, 0x5500800389, load, 0x550080038a, load, 0x550080038b, load, 0x550080038c, load, 0x550080038d, load, 0x550080038e, load, 0x550080038f, load, 0x5500800390, load, 0x5500800391, load, 0x5500800392, load, 0x5500800393, load, 0x5500800394, load, 0x5500800395, load, 0x5500800396, load, 0x5500800397, load, 0x5500800398, load, 0x5500800399, load, 0x550080039a, load, 0x550080039b, load, 0x550080039c, load, 0x550080039d, load, 0x550080039e, load, 0x550080039f, load, 0x55008003a0, load, 0x55008003a1, load, 0x55008003a2, load, 0x55008003a3, load, 0x55008003a4, load, 0x55008003a5, load, 0x55008003a6, load, 0x55008003a7, load, 0x55008003a8, load, 0x55008003a9, load, 0x55008003aa, load, 0x55008003ab, load, 0x55008003ac, load, 0x55008003ad, load, 0x55008003ae, load, 0x55008003af

(4007c0 is the ld1b in the sha512-sve)

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Cc: Robert Henry <robhenry@microsoft.com>
Cc: Aaron Lindsay <aaron@os.amperecomputing.com>
---
 include/exec/cpu-all.h            |  2 +-
 include/hw/core/cpu.h             | 17 +++++++++++++++++
 accel/tcg/cputlb.c                |  4 +++-
 accel/tcg/user-exec.c             |  6 +++++-
 target/arm/tcg/sve_helper.c       |  4 ----
 tests/tcg/aarch64/Makefile.target |  8 ++++++++
 6 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 78d258af44..9ab09cf7c2 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -301,7 +301,7 @@ CPUArchState *cpu_copy(CPUArchState *env);
  * be signaled by probe_access_flags().
  */
 #define TLB_INVALID_MASK    (1 << (TARGET_PAGE_BITS_MIN - 1))
-#define TLB_MMIO            0
+#define TLB_MMIO            (1 << (TARGET_PAGE_BITS_MIN - 2))
 #define TLB_WATCHPOINT      0
 
 #else
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 39150cf8f8..26fadf7e62 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -983,6 +983,23 @@ void cpu_watchpoint_remove_by_ref(CPUState *cpu, CPUWatchpoint *watchpoint);
 void cpu_watchpoint_remove_all(CPUState *cpu, int mask);
 #endif
 
+/**
+ * cpu_plugin_mem_cbs_enabled() - are plugin memory callbacks enabled?
+ * @cs: CPUState pointer
+ *
+ * The memory callbacks are installed if a plugin has instrumented an
+ * instruction for memory. This can be useful to know if you want to
+ * force a slow path for a series of memory accesses.
+ */
+static inline bool cpu_plugin_mem_cbs_enabled(const CPUState *cpu)
+{
+#ifdef CONFIG_PLUGIN
+    return !!cpu->plugin_mem_cbs;
+#else
+    return false;
+#endif
+}
+
 /**
  * cpu_get_address_space:
  * @cpu: CPU to get address space from
diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index ae0fbcdee2..f117fd8f16 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1540,7 +1540,9 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr,
     *pfull = &env_tlb(env)->d[mmu_idx].fulltlb[index];
 
     /* Fold all "mmio-like" bits into TLB_MMIO.  This is not RAM.  */
-    if (unlikely(flags & ~(TLB_WATCHPOINT | TLB_NOTDIRTY))) {
+    if (unlikely(flags & ~(TLB_WATCHPOINT | TLB_NOTDIRTY))
+        ||
+        (access_type != MMU_INST_FETCH && cpu_plugin_mem_cbs_enabled(env_cpu(env)))) {
         *phost = NULL;
         return TLB_MMIO;
     }
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index 36ad8284a5..383263cd1d 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -745,6 +745,10 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr,
     if (guest_addr_valid_untagged(addr)) {
         int page_flags = page_get_flags(addr);
         if (page_flags & acc_flag) {
+            if ((acc_flag == PAGE_READ || acc_flag == PAGE_WRITE)
+                && cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
+                return TLB_MMIO;
+            }
             return 0; /* success */
         }
         maperr = !(page_flags & PAGE_VALID);
@@ -767,7 +771,7 @@ int probe_access_flags(CPUArchState *env, target_ulong addr, int size,
 
     g_assert(-(addr | TARGET_PAGE_MASK) >= size);
     flags = probe_access_internal(env, addr, size, access_type, nonfault, ra);
-    *phost = flags ? NULL : g2h(env_cpu(env), addr);
+    *phost = (flags & TLB_INVALID_MASK) ? NULL : g2h(env_cpu(env), addr);
     return flags;
 }
 
diff --git a/target/arm/tcg/sve_helper.c b/target/arm/tcg/sve_helper.c
index 0097522470..7c103fc9f7 100644
--- a/target/arm/tcg/sve_helper.c
+++ b/target/arm/tcg/sve_helper.c
@@ -5688,9 +5688,6 @@ void sve_ldN_r(CPUARMState *env, uint64_t *vg, const target_ulong addr,
 
     flags = info.page[0].flags | info.page[1].flags;
     if (unlikely(flags != 0)) {
-#ifdef CONFIG_USER_ONLY
-        g_assert_not_reached();
-#else
         /*
          * At least one page includes MMIO.
          * Any bus operation can fail with cpu_transaction_failed,
@@ -5727,7 +5724,6 @@ void sve_ldN_r(CPUARMState *env, uint64_t *vg, const target_ulong addr,
             memcpy(&env->vfp.zregs[(rd + i) & 31], &scratch[i], reg_max);
         }
         return;
-#endif
     }
 
     /* The entire operation is in RAM, on valid pages. */
diff --git a/tests/tcg/aarch64/Makefile.target b/tests/tcg/aarch64/Makefile.target
index 0315795487..f83edd8544 100644
--- a/tests/tcg/aarch64/Makefile.target
+++ b/tests/tcg/aarch64/Makefile.target
@@ -80,6 +80,14 @@ sha512-vector: sha512.c
 
 TESTS += sha512-vector
 
+ifneq ($(CROSS_CC_HAS_SVE),)
+sha512-sve: CFLAGS=-O3 -march=armv8.1-a+sve
+sha512-sve: sha512.c
+	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) $< -o $@ $(LDFLAGS)
+
+TESTS += sha512-sve
+endif
+
 ifeq ($(HOST_GDB_SUPPORTS_ARCH),y)
 GDB_SCRIPT=$(SRC_PATH)/tests/guest-debug/run-test.py
 
-- 
2.39.2