[Qemu-devel] [RFC v8 06/14] qom: cpu: Add CPUClass hooks for exclusive range

[Alvise Rigo <a.rigo@virtualopensystems.com>]

The excl_protected_range is a hwaddr range set by the VCPU at the
execution of a LoadLink instruction. If a normal access writes to this
range, the corresponding StoreCond will fail.

Each architecture can set the exclusive range when issuing the LoadLink
operation through a CPUClass hook. This comes in handy to emulate, for
instance, the exclusive monitor implemented in some ARM architectures
(more precisely, the Exclusive Reservation Granule).

In addition, add another CPUClass hook called to decide whether a
StoreCond has to fail or not.

Suggested-by: Jani Kokkonen <jani.kokkonen@huawei.com>
Suggested-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>
---
 include/qom/cpu.h | 20 ++++++++++++++++++++
 qom/cpu.c         | 27 +++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 2e5229d..21f10eb 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -29,6 +29,7 @@
 #include "qemu/queue.h"
 #include "qemu/thread.h"
 #include "qemu/typedefs.h"
+#include "qemu/range.h"
 
 typedef int (*WriteCoreDumpFunction)(const void *buf, size_t size,
                                      void *opaque);
@@ -123,6 +124,10 @@ struct TranslationBlock;
  * @cpu_exec_enter: Callback for cpu_exec preparation.
  * @cpu_exec_exit: Callback for cpu_exec cleanup.
  * @cpu_exec_interrupt: Callback for processing interrupts in cpu_exec.
+ * @cpu_set_excl_protected_range: Callback used by LL operation for setting the
+ *                                exclusive range.
+ * @cpu_valid_excl_access: Callback for checking the validity of a SC operation.
+ * @cpu_reset_excl_context: Callback for resetting the exclusive context.
  * @disas_set_info: Setup architecture specific components of disassembly info
  *
  * Represents a CPU family or model.
@@ -183,6 +188,13 @@ typedef struct CPUClass {
     void (*cpu_exec_exit)(CPUState *cpu);
     bool (*cpu_exec_interrupt)(CPUState *cpu, int interrupt_request);
 
+    /* Atomic instruction handling */
+    void (*cpu_set_excl_protected_range)(CPUState *cpu, hwaddr addr,
+                                         hwaddr size);
+    bool (*cpu_valid_excl_access)(CPUState *cpu, hwaddr addr,
+                                 hwaddr size);
+    void (*cpu_reset_excl_context)(CPUState *cpu);
+
     void (*disas_set_info)(CPUState *cpu, disassemble_info *info);
 } CPUClass;
 
@@ -219,6 +231,9 @@ struct kvm_run;
 #define TB_JMP_CACHE_BITS 12
 #define TB_JMP_CACHE_SIZE (1 << TB_JMP_CACHE_BITS)
 
+/* Atomic insn translation TLB support. */
+#define EXCLUSIVE_RESET_ADDR ULLONG_MAX
+
 /**
  * CPUState:
  * @cpu_index: CPU index (informative).
@@ -341,6 +356,11 @@ struct CPUState {
      */
     bool throttle_thread_scheduled;
 
+    /* vCPU's exclusive addresses range.
+     * The address is set to EXCLUSIVE_RESET_ADDR if the vCPU is not
+     * in the middle of a LL/SC. */
+    struct Range excl_protected_range;
+
     /* Note that this is accessed at the start of every TB via a negative
        offset from AREG0.  Leave this field at the end so as to make the
        (absolute value) offset as small as possible.  This reduces code
diff --git a/qom/cpu.c b/qom/cpu.c
index 8f537a4..309d487 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -203,6 +203,29 @@ static bool cpu_common_exec_interrupt(CPUState *cpu, int int_req)
     return false;
 }
 
+static void cpu_common_set_excl_range(CPUState *cpu, hwaddr addr, hwaddr size)
+{
+    cpu->excl_protected_range.begin = addr;
+    cpu->excl_protected_range.end = addr + size;
+}
+
+static bool cpu_common_valid_excl_access(CPUState *cpu, hwaddr addr, hwaddr size)
+{
+    /* Check if the excl range completely covers the access */
+    if (cpu->excl_protected_range.begin <= addr &&
+        cpu->excl_protected_range.end >= addr + size) {
+
+        return true;
+    }
+
+    return false;
+}
+
+static void cpu_common_reset_excl_context(CPUState *cpu)
+{
+    cpu->excl_protected_range.begin = EXCLUSIVE_RESET_ADDR;
+}
+
 void cpu_dump_state(CPUState *cpu, FILE *f, fprintf_function cpu_fprintf,
                     int flags)
 {
@@ -252,6 +275,7 @@ static void cpu_common_reset(CPUState *cpu)
     cpu->can_do_io = 1;
     cpu->exception_index = -1;
     cpu->crash_occurred = false;
+    cpu_common_reset_excl_context(cpu);
     memset(cpu->tb_jmp_cache, 0, TB_JMP_CACHE_SIZE * sizeof(void *));
 }
 
@@ -355,6 +379,9 @@ static void cpu_class_init(ObjectClass *klass, void *data)
     k->cpu_exec_enter = cpu_common_noop;
     k->cpu_exec_exit = cpu_common_noop;
     k->cpu_exec_interrupt = cpu_common_exec_interrupt;
+    k->cpu_set_excl_protected_range = cpu_common_set_excl_range;
+    k->cpu_valid_excl_access = cpu_common_valid_excl_access;
+    k->cpu_reset_excl_context = cpu_common_reset_excl_context;
     dc->realize = cpu_common_realizefn;
     /*
      * Reason: CPUs still need special care by board code: wiring up
-- 
2.8.0