Re: [Qemu-devel] [PATCH v2 05/31] vl.c: extend -m option to support options for memory hotplug

[Andrey Korolyov]

On Wed, May 21, 2014 at 12:10 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Tue, May 20, 2014 at 05:15:08PM +0200, Igor Mammedov wrote:
>> Add following parameters:
>>   "slots" - total number of hotplug memory slots
>>   "maxmem" - maximum possible memory
>>
>> "slots" and "maxmem" should go in pair and "maxmem" should be greater
>> than "mem" for memory hotplug to be enabled.
>>
>> Signed-off-by: Igor Mammedov <address@hidden>
>
> Also, it's a bug to mix this with a compat machine type, right?
> Maybe best to fail initialization if users try this.
>
>> ---
>> v4:
>>  - store maxmem & slots values in MachineState
>> v3:
>>  - store maxmem & slots values in QEMUMachineInitArgs
>> v2:
>>  - rebased on top of the latest "vl: convert -m to QemuOpts"
>> ---
>>  include/hw/boards.h |    3 ++-
>>  qemu-options.hx     |    9 ++++++---
>>  vl.c                |   51 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 59 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>> index b62de4a..f6fbbe1 100644
>> --- a/include/hw/boards.h
>> +++ b/include/hw/boards.h
>> @@ -8,7 +8,6 @@
>>  #include "hw/qdev.h"
>>  #include "qom/object.h"
>>
>> -
>>  typedef struct MachineState MachineState;
>>
>>  typedef void QEMUMachineInitFunc(MachineState *ms);
>> @@ -113,6 +112,8 @@ struct MachineState {
>>      char *firmware;
>>
>>      ram_addr_t ram_size;
>> +    ram_addr_t maxram_size;
>> +    uint64_t   ram_slots;
>>      const char *boot_order;
>>      const char *kernel_filename;
>>      const char *kernel_cmdline;
>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index 781af14..c6411c4 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -210,17 +210,20 @@ use is discouraged as it may be removed from future 
>> versions.
>>  ETEXI
>>
>>  DEF("m", HAS_ARG, QEMU_OPTION_m,
>> -    "-m [size=]megs\n"
>> +    "-m[emory] [size=]megs[,slots=n,maxmem=size]\n"
>>      "                configure guest RAM\n"
>>      "                size: initial amount of guest memory (default: "
>> -    stringify(DEFAULT_RAM_SIZE) "MiB)\n",
>> +    stringify(DEFAULT_RAM_SIZE) "MiB)\n"
>> +    "                slots: number of hotplug slots (default: none)\n"
>> +    "                maxmem: maximum amount of guest memory (default: 
>> none)\n",
>>      QEMU_ARCH_ALL)
>>  STEXI
>>  @item -m address@hidden
>>  @findex -m
>>  Set virtual RAM size to @var{megs} megabytes. Default is 128 MiB.  
>> Optionally,
>>  a suffix of ``M'' or ``G'' can be used to signify a value in megabytes or
>> -gigabytes respectively.
>> +gigabytes respectively. Optional pair @var{slots}, @var{maxmem} could be 
>> used
>> +to set amount of hotluggable memory slots and possible maximum amount of 
>> memory.
>>  ETEXI
>>
>>  DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
>> diff --git a/vl.c b/vl.c
>> index 8fd4ed9..9fb6fa4 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -520,6 +520,14 @@ static QemuOptsList qemu_mem_opts = {
>>              .name = "size",
>>              .type = QEMU_OPT_SIZE,
>>          },
>> +        {
>> +            .name = "slots",
>> +            .type = QEMU_OPT_NUMBER,
>> +        },
>> +        {
>> +            .name = "maxmem",
>> +            .type = QEMU_OPT_SIZE,
>> +        },
>>          { /* end of list */ }
>>      },
>>  };
>> @@ -2989,6 +2997,8 @@ int main(int argc, char **argv, char **envp)
>>      const char *trace_file = NULL;
>>      const ram_addr_t default_ram_size = (ram_addr_t)DEFAULT_RAM_SIZE *
>>                                          1024 * 1024;
>> +    ram_addr_t maxram_size = default_ram_size;
>> +    uint64_t ram_slots = 0;
>>
>>      atexit(qemu_run_exit_notifiers);
>>      error_set_progname(argv[0]);
>> @@ -3324,6 +3334,7 @@ int main(int argc, char **argv, char **envp)
>>              case QEMU_OPTION_m: {
>>                  uint64_t sz;
>>                  const char *mem_str;
>> +                const char *maxmem_str, *slots_str;
>>
>>                  opts = qemu_opts_parse(qemu_find_opts("memory"),
>>                                         optarg, 1);
>> @@ -3365,6 +3376,44 @@ int main(int argc, char **argv, char **envp)
>>                      error_report("ram size too large");
>>                      exit(EXIT_FAILURE);
>>                  }
>> +
>> +                maxmem_str = qemu_opt_get(opts, "maxmem");
>> +                slots_str = qemu_opt_get(opts, "slots");
>> +                if (maxmem_str && slots_str) {
>> +                    uint64_t slots;
>> +
>> +                    sz = qemu_opt_get_size(opts, "maxmem", 0);
>> +                    if (sz < ram_size) {
>> +                        fprintf(stderr, "qemu: invalid -m option value: 
>> maxmem "
>> +                                "(%" PRIu64 ") <= initial memory (%"
>> +                                PRIu64 ")\n", sz, ram_size);
>> +                        exit(EXIT_FAILURE);
>> +                    }
>> +
>> +                    slots = qemu_opt_get_number(opts, "slots", 0);
>> +                    if ((sz > ram_size) && !slots) {
>> +                        fprintf(stderr, "qemu: invalid -m option value: 
>> maxmem "
>> +                                "(%" PRIu64 ") more than initial memory (%"
>> +                                PRIu64 ") but no hotplug slots where "
>> +                                "specified\n", sz, ram_size);
>> +                        exit(EXIT_FAILURE);
>> +                    }
>> +
>> +                    if ((sz <= ram_size) && slots) {
>> +                        fprintf(stderr, "qemu: invalid -m option value:  %"
>> +                                PRIu64 " hotplug slots where specified but "
>> +                                "maxmem (%" PRIu64 ") <= initial memory (%"
>> +                                PRIu64 ")\n", slots, sz, ram_size);
>> +                        exit(EXIT_FAILURE);
>> +                    }
>> +                    maxram_size = sz;
>> +                    ram_slots = slots;
>> +                } else if ((!maxmem_str && slots_str) ||
>> +                           (maxmem_str && !slots_str)) {
>> +                    fprintf(stderr, "qemu: invalid -m option value: missing 
>> "
>> +                            "'%s' option\n", slots_str ? "maxmem" : 
>> "slots");
>> +                    exit(EXIT_FAILURE);
>> +                }
>>                  break;
>>              }
>>  #ifdef CONFIG_TPM
>> @@ -4422,6 +4471,8 @@ int main(int argc, char **argv, char **envp)
>>      qdev_machine_init();
>>
>>      current_machine->ram_size = ram_size;
>> +    current_machine->maxram_size = maxram_size;
>> +    current_machine->ram_slots = ram_slots;
>>      current_machine->boot_order = boot_order;
>>      current_machine->kernel_filename = kernel_filename;
>>      current_machine->kernel_cmdline = kernel_cmdline;
>> --
>> 1.7.1

May be I am adding very userish opinion, but ability to specify slot
state via cmdline explicitly, like in
https://github.com/vliaskov/qemu-kvm/tree/memhp-v5-wip, looks better
in sight of thoughts of future integration in libvirt and for unplug
option (where knowledge of which regions are offlined is necessary to
do the job).