Re: [PATCH] softmmu/vl.c: fix too slow TCG regression

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

Igor Mammedov <imammedo@redhat.com> writes:

> Commit a1b18df9a4 moved -m option parsing after configure_accelerators()
> that broke TCG accelerator initialization which accesses global ram_size
> from size_code_gen_buffer() which is equal to 0 at that moment.
>
> Partially revert a1b18df9a4, by returning set_memory_options() to its
> original location and only keep 32-bit host VA check and 'memory-backend'
> size check introduced by fe64d06afc at current place.
>
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
>
> PS:
> This should take care of regression and give more time to think about
> how to remove size_code_gen_buffer() dependency on ram_size

Tested-by: Alex Bennée <alex.bennee@linaro.org>

FWIW I don't think it will take too long to fixup size_code_gen_buffer.
See:

  Subject: [PATCH  v1 0/4] Fix codegen translation cache size 
  Date: Wed, 26 Feb 2020 18:10:16 +0000
  Message-Id: <20200226181020.19592-1-alex.bennee@linaro.org>


> ---
>  softmmu/vl.c | 49 +++++++++++++++++++++++++------------------------
>  1 file changed, 25 insertions(+), 24 deletions(-)
>
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index a9cce78f45..da7577129c 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2634,29 +2634,6 @@ static void set_memory_options(uint64_t *ram_slots, ram_addr_t *maxram_size,
>          exit(EXIT_FAILURE);
>      }
>  
> -    if (current_machine->ram_memdev_id) {
> -        Object *backend;
> -        ram_addr_t backend_size;
> -
> -        backend = object_resolve_path_type(current_machine->ram_memdev_id,
> -                                           TYPE_MEMORY_BACKEND, NULL);
> -        backend_size = object_property_get_uint(backend, "size",  &error_abort);
> -        if (mem_str && backend_size != ram_size) {
> -                error_report("Size specified by -m option must match size of "
> -                             "explicitly specified 'memory-backend' property");
> -                exit(EXIT_FAILURE);
> -        }
> -        ram_size = backend_size;
> -    }
> -
> -    if (!xen_enabled()) {
> -        /* On 32-bit hosts, QEMU is limited by virtual address space */
> -        if (ram_size > (2047 << 20) && HOST_LONG_BITS == 32) {
> -            error_report("at most 2047 MB RAM can be simulated");
> -            exit(1);
> -        }
> -    }
> -
>      loc_pop(&loc);
>  }
>  
> @@ -3821,6 +3798,8 @@ void qemu_init(int argc, char **argv, char **envp)
>      machine_class = select_machine();
>      object_set_machine_compat_props(machine_class->compat_props);
>  
> +    set_memory_options(&ram_slots, &maxram_size, machine_class);
> +
>      os_daemonize();
>  
>      /*
> @@ -4296,7 +4275,29 @@ void qemu_init(int argc, char **argv, char **envp)
>          current_machine->cpu_type = parse_cpu_option(cpu_option);
>      }
>  
> -    set_memory_options(&ram_slots, &maxram_size, machine_class);
> +    if (!xen_enabled()) {
> +        /* On 32-bit hosts, QEMU is limited by virtual address space */
> +        if (ram_size > (2047 << 20) && HOST_LONG_BITS == 32) {
> +            error_report("at most 2047 MB RAM can be simulated");
> +            exit(1);
> +        }
> +    }
> +
> +    if (current_machine->ram_memdev_id) {
> +        Object *backend;
> +        ram_addr_t backend_size;
> +
> +        backend = object_resolve_path_type(current_machine->ram_memdev_id,
> +                                           TYPE_MEMORY_BACKEND, NULL);
> +        backend_size = object_property_get_uint(backend, "size",  &error_abort);
> +        if (backend_size != ram_size) {
> +                error_report("Size specified by -m option must match size of "
> +                             "explicitly specified 'memory-backend' property");
> +                exit(EXIT_FAILURE);
> +        }
> +        ram_size = backend_size;
> +    }
> +
>      current_machine->ram_size = ram_size;
>      current_machine->maxram_size = maxram_size;
>      current_machine->ram_slots = ram_slots;


-- 
Alex Bennée