qemu/hw-i386-add-mem2-option-for-qemu.patch

From d29bc8738131dcaaa1a1ae2870ea29b59a137f30 Mon Sep 17 00:00:00 2001
From: xiongmengbiao <xiongmengbiao@hygon.cn>
Date: Wed, 29 May 2024 00:05:44 +0800
Subject: [PATCH] hw/i386: add mem2 option for qemu

The '-mem2' option is used to create a set of hugepages
of memory and map them to a fixed address range of the guest.

This allows some devices to easily obtain continuous host
physical address ranges for performing DMA operations.

Signed-off-by: xiongmengbiao <xiongmengbiao@hygon.cn>
---
 hw/i386/pc.c        | 121 ++++++++++++++++++++++++++++++++++++++++++++
 include/hw/boards.h |   2 +
 qemu-options.hx     |  12 +++++
 system/vl.c         |  76 ++++++++++++++++++++++++++++
 4 files changed, 211 insertions(+)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 29b9964733..204e34db86 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -743,6 +743,111 @@ void xen_load_linux(PCMachineState *pcms)
     x86ms->fw_cfg = fw_cfg;
 }
 
+static int try_create_2MB_page(uint32_t page_num)
+{
+    char nr_hp_num_s[256] = {0};
+    char free_hp_num_s[256] = {0};
+    const char *nr_hugepages_dir = "/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages";
+    const char *free_hugepages_dir = "/sys/kernel/mm/hugepages/hugepages-2048kB/free_hugepages";
+    int nr_hp_num = -1, free_hp_num = -1, ret = -1;
+    int nr_fd = qemu_open_old(nr_hugepages_dir, O_RDWR);
+    int free_fd = qemu_open_old(free_hugepages_dir, O_RDONLY);
+
+    if (nr_fd < 0 || free_fd < 0) {
+        error_report("%s: qemu_open failed: %s\n", __func__, strerror(errno));
+        goto end;
+    }
+
+    if (read(nr_fd, nr_hp_num_s, 256) < 0)
+        goto end;
+    if (read(free_fd, free_hp_num_s, 256) < 0)
+        goto end;
+
+    nr_hp_num = atoi(nr_hp_num_s);
+    free_hp_num = atoi(free_hp_num_s);
+    if (nr_hp_num < 0 || free_hp_num < 0)
+        goto end;
+
+    if (page_num <= free_hp_num) {
+        ret = 0;
+        goto end;
+    }
+
+    nr_hp_num += (page_num - free_hp_num);
+    snprintf (nr_hp_num_s, 256, "%d", nr_hp_num);
+    if (write(nr_fd, nr_hp_num_s, strlen(nr_hp_num_s)) < 0)
+        goto end;
+
+    ret = 0;
+end:
+    if (nr_fd >= 0)
+        close(nr_fd);
+    if (free_fd >= 0)
+        close(free_fd);
+    return ret;
+}
+
+#define HUGEPAGE_NUM_MAX  128
+#define HUGEPAGE_SIZE     (1024*1024*2)
+static void mem2_init(MachineState *ms, MemoryRegion *system_memory)
+{
+    MemoryRegion *mem2_mr;
+    char mr_name[128] = {0};
+    void *ram = NULL;
+    int ret = 0, lock_fd;
+    const char *lock_file = "/sys/kernel/mm/hugepages/hugepages-2048kB/nr_overcommit_hugepages";
+    uint32_t page_num = ms->ram2_size / HUGEPAGE_SIZE, i;
+
+    if (HUGEPAGE_NUM_MAX < page_num) {
+        error_report("\"-mem2 'size='\" needs to Less than %dM\n",
+                        (HUGEPAGE_SIZE * HUGEPAGE_NUM_MAX) / (1024 * 1024));
+        exit(EXIT_FAILURE);
+    }
+
+    // Apply for hugepages from OS and use them, which needs to be synchronized
+    lock_fd = qemu_open_old(lock_file, O_WRONLY);
+    if (lock_fd < 0) {
+        error_report("%s: open %s failed: %s\n", __func__, lock_file, strerror(errno));
+        exit(EXIT_FAILURE);
+    }
+
+    while (qemu_lock_fd(lock_fd, 0, 0, true)) {
+        if (errno != EACCES && errno != EAGAIN) {
+            error_report("qemu_lock_fd failed: %s\n", strerror(errno));
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    /** try to create hugepage.
+     *  If there are enough free hugepages, then do nothing.
+     */
+    ret = try_create_2MB_page(page_num);
+    if (ret) {
+        error_report("%s: Failed to allocate hugepage\n", __func__);
+        goto unlock;
+    }
+
+    for (i = 0; i < page_num; ++i) {
+        mem2_mr = g_malloc(sizeof(*mem2_mr));
+        ram = mmap(NULL, HUGEPAGE_SIZE, PROT_READ | PROT_WRITE,
+                    MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE | MAP_HUGETLB, -1, 0);
+        if (ram == MAP_FAILED) {
+            error_report("%s: mmap failed: %s", __func__, strerror(errno));
+            goto unlock;
+        }
+
+        sprintf(mr_name, "mem2-%d", i);
+        memory_region_init_ram_ptr(mem2_mr, NULL, mr_name, HUGEPAGE_SIZE, ram);
+        memory_region_add_subregion(system_memory, ms->ram2_base + (i * HUGEPAGE_SIZE), mem2_mr);
+    }
+
+    ret = 0;
+unlock:
+    qemu_unlock_fd(lock_fd, 0, 0);
+    if (ret)
+        exit(EXIT_FAILURE);
+}
+
 #define PC_ROM_MIN_VGA     0xc0000
 #define PC_ROM_MIN_OPTION  0xc8000
 #define PC_ROM_MAX         0xe0000
@@ -965,6 +1070,22 @@ void pc_memory_init(PCMachineState *pcms,
                        E820_RAM);
     }
 
+    if (machine->ram2_size && machine->ram2_base) {
+        if (0x100000000ULL + x86ms->above_4g_mem_size > machine->ram2_base) {
+            error_report("\"-mem2 'base'\" needs to greater 0x%llx\n",
+                            0x100000000ULL + x86ms->above_4g_mem_size);
+            exit(EXIT_FAILURE);
+        }
+        if (machine->ram2_base & (HUGEPAGE_SIZE - 1) ||
+                machine->ram2_size & (HUGEPAGE_SIZE - 1)) {
+            error_report("\"-mem2 'base|size'\" needs to aligned to 0x%x\n", HUGEPAGE_SIZE);
+            exit(EXIT_FAILURE);
+        }
+
+        mem2_init(machine, system_memory);
+        e820_add_entry(machine->ram2_base, machine->ram2_size, E820_RAM);
+    }
+
     if (pcms->sgx_epc.size != 0) {
         e820_add_entry(pcms->sgx_epc.base, pcms->sgx_epc.size, E820_RESERVED);
     }
diff --git a/include/hw/boards.h b/include/hw/boards.h
index da85f86efb..8ac8cad2a2 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -389,6 +389,8 @@ struct MachineState {
 
     ram_addr_t ram_size;
     ram_addr_t maxram_size;
+    ram_addr_t ram2_base;
+    ram_addr_t ram2_size;
     uint64_t   ram_slots;
     BootConfiguration boot_config;
     char *kernel_filename;
diff --git a/qemu-options.hx b/qemu-options.hx
index 42fd09e4de..bc8e66a037 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -5845,6 +5845,18 @@ SRST
             (qemu) qom-set /objects/iothread1 poll-max-ns 100000
 ERST
 
+DEF("mem2", HAS_ARG, QEMU_OPTION_mem2,
+    "-mem2 base=addr[G],size=n[MG]\n"
+    "                Map guest memory using host hugepages\n"
+    "                base: starting position of guest physical address\n"
+    "                size: the size of mmaped memory\n"
+    "NOTE: Both `base` and `size` need to be aligned according to 2MB\n",
+    QEMU_ARCH_I386)
+SRST
+``-mem2 base=addr[G],size=n[MG]``
+    Map the host's large page memory at the specified guest address
+    so that some devices can use larger contiguous physical memory.
+ERST
 
 HXCOMM This is the last statement. Insert new options before this line!
 
diff --git a/system/vl.c b/system/vl.c
index 8e3357c578..a1e5e68773 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -173,6 +173,8 @@ static QemuPluginList plugin_list = QTAILQ_HEAD_INITIALIZER(plugin_list);
 static BlockdevOptionsQueue bdo_queue = QSIMPLEQ_HEAD_INITIALIZER(bdo_queue);
 static bool nographic = false;
 static int mem_prealloc; /* force preallocation of physical target memory */
+static ram_addr_t ram2_base;
+static ram_addr_t ram2_size;
 static const char *vga_model = NULL;
 static DisplayOptions dpy;
 static int num_serial_hds;
@@ -504,6 +506,23 @@ static QemuOptsList qemu_action_opts = {
     },
 };
 
+static QemuOptsList qemu_mem2_opts = {
+    .name = "mem2",
+    .merge_lists = true,
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_mem2_opts.head),
+    .desc = {
+        {
+            .name = "base",
+            .type = QEMU_OPT_SIZE,
+        },
+        {
+            .name = "size",
+            .type = QEMU_OPT_SIZE,
+        },
+        { /* end of list */ }
+    },
+};
+
 const char *qemu_get_vm_name(void)
 {
     return qemu_name;
@@ -1932,6 +1951,9 @@ static void qemu_apply_machine_options(QDict *qdict)
 {
     object_set_properties_from_keyval(OBJECT(current_machine), qdict, false, &error_fatal);
 
+    current_machine->ram2_size = ram2_size;
+    current_machine->ram2_base = ram2_base;
+
     if (semihosting_enabled(false) && !semihosting_get_argc()) {
         /* fall back to the -kernel/-append */
         semihosting_arg_fallback(current_machine->kernel_filename, current_machine->kernel_cmdline);
@@ -2094,11 +2116,57 @@ static void parse_memory_options(void)
     loc_pop(&loc);
 }
 
+static void set_mem2_options(void)
+{
+    uint64_t sz, base;
+    const char *mem_str;
+    QemuOpts *opts = qemu_find_opts_singleton("mem2");
+    Location loc;
+
+    loc_push_none(&loc);
+    qemu_opts_loc_restore(opts);
+
+    mem_str = qemu_opt_get(opts, "base");
+    if (mem_str) {
+        if (!*mem_str) {
+            error_report("missing 'base' option value");
+            exit(EXIT_FAILURE);
+        }
+
+        base = qemu_opt_get_size(opts, "base", ram2_base);
+        ram2_base = base;
+    }
+
+    mem_str = qemu_opt_get(opts, "size");
+    if (mem_str) {
+        if (!*mem_str) {
+            error_report("missing 'base' option value");
+            exit(EXIT_FAILURE);
+        }
+
+        sz = qemu_opt_get_size(opts, "size", ram2_size);
+        ram2_size = sz;
+    }
+
+    if (ram2_base && !ram2_size){
+        error_report("missing 'size' option value");
+        exit(EXIT_FAILURE);
+    }
+    if (!ram2_base && ram2_size){
+        error_report("missing 'base' option value");
+        exit(EXIT_FAILURE);
+    }
+
+    loc_pop(&loc);
+}
+
 static void qemu_create_machine(QDict *qdict)
 {
     MachineClass *machine_class = select_machine(qdict, &error_fatal);
     object_set_machine_compat_props(machine_class->compat_props);
 
+    set_mem2_options();
+
     current_machine = MACHINE(object_new_with_class(OBJECT_CLASS(machine_class)));
     object_property_add_child(object_get_root(), "machine",
                               OBJECT(current_machine));
@@ -2777,6 +2845,7 @@ void qemu_init(int argc, char **argv)
     qemu_add_opts(&qemu_semihosting_config_opts);
     qemu_add_opts(&qemu_fw_cfg_opts);
     qemu_add_opts(&qemu_action_opts);
+    qemu_add_opts(&qemu_mem2_opts);
     qemu_add_run_with_opts();
     module_call_init(MODULE_INIT_OPTS);
 
@@ -3596,6 +3665,13 @@ void qemu_init(int argc, char **argv)
             case QEMU_OPTION_nouserconfig:
                 /* Nothing to be parsed here. Especially, do not error out below. */
                 break;
+            case QEMU_OPTION_mem2:
+                opts = qemu_opts_parse_noisily(qemu_find_opts("mem2"),
+                                               optarg, false);
+                if (!opts) {
+                    exit(EXIT_FAILURE);
+                }
+                break;
 #if defined(CONFIG_POSIX)
             case QEMU_OPTION_runas:
                 if (!os_set_runas(optarg)) {
-- 
2.41.0.windows.1