[Qemu-devel] [RFC 1/8] vl.c: extend -m option to support options for memory hotplug

[Igor Mammedov <imammedo@redhat.com>]

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 <imammedo@redhat.com>
---
v3:
 - store maxmem & slots valus in QEMUMachineInitArgs
v2:
 - rebased on top of the latest "vl: convert -m to QemuOpts"
---
 include/hw/boards.h |    2 ++
 qemu-options.hx     |    9 ++++++---
 vl.c                |   51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/include/hw/boards.h b/include/hw/boards.h
index 7bd2ea7..22d9496 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -10,6 +10,8 @@
 typedef struct QEMUMachineInitArgs {
     const QEMUMachine *machine;
     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 7482750..add34c4 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 [size=]@var{megs}
 @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 4b36bde..7bae6fe 100644
--- a/vl.c
+++ b/vl.c
@@ -517,6 +517,14 @@ 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 */ }
     },
 };
@@ -2946,6 +2954,8 @@ 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]);
@@ -3291,6 +3301,7 @@ 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);
@@ -3332,6 +3343,44 @@ 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
@@ -4389,6 +4438,8 @@ int main(int argc, char **argv, char **envp)
 
     QEMUMachineInitArgs args = { .machine = machine,
                                  .ram_size = ram_size,
+                                 .maxram_size = maxram_size,
+                                 .ram_slots = ram_slots,
                                  .boot_order = boot_order,
                                  .kernel_filename = kernel_filename,
                                  .kernel_cmdline = kernel_cmdline,
-- 
1.7.1