Re: [Qemu-devel] [RFC v7 06/16] qom: cpu: Add CPUClass hooks for exclusive range

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

Alvise Rigo <a.rigo@virtualopensystems.com> writes:

> 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 | 15 +++++++++++++++
>  qom/cpu.c         | 20 ++++++++++++++++++++
>  2 files changed, 35 insertions(+)
>
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 2e5229d..682c81d 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);
> @@ -183,6 +184,12 @@ 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);
> +    int (*cpu_valid_excl_access)(CPUState *cpu, hwaddr addr,
> +                                 hwaddr size);
> +
>      void (*disas_set_info)(CPUState *cpu, disassemble_info *info);
>  } CPUClass;
>
> @@ -219,6 +226,9 @@ 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 +351,11 @@ 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;
> +

In which case we should probably initialise that on CPU creation as we
don't start in the middle of a LL/SC.

>      /* 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..a5d360c 100644
> --- a/qom/cpu.c
> +++ b/qom/cpu.c
> @@ -203,6 +203,24 @@ 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 int 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 1;
> +    }
> +
> +    return 0;
> +}

This can be a bool function.

> +
>  void cpu_dump_state(CPUState *cpu, FILE *f, fprintf_function cpu_fprintf,
>                      int flags)
>  {
> @@ -355,6 +373,8 @@ 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;
>      dc->realize = cpu_common_realizefn;
>      /*
>       * Reason: CPUs still need special care by board code: wiring up


--
Alex Bennée