[PATCH v2] pc: add property for Linux setup_data random number seed

[Paolo Bonzini]

Using a property makes it possible to use the normal compat property
mechanism instead of ad hoc code; it avoids parameter proliferation
in x86_load_linux; and allows shipping the code even if it is
disabled by default.

Cc: Michael S. Tsirkin <mst@redhat.com>
Co-developed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/i386/microvm.c     |  2 +-
 hw/i386/pc.c          |  5 +++--
 hw/i386/pc_piix.c     |  2 +-
 hw/i386/pc_q35.c      |  2 +-
 hw/i386/x86.c         | 33 +++++++++++++++++++++++++++++----
 include/hw/i386/pc.h  |  3 ---
 include/hw/i386/x86.h |  5 +++--
 7 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
index 7fe8cce03e..dc929727dc 100644
--- a/hw/i386/microvm.c
+++ b/hw/i386/microvm.c
@@ -332,7 +332,7 @@ static void microvm_memory_init(MicrovmMachineState *mms)
     rom_set_fw(fw_cfg);
 
     if (machine->kernel_filename != NULL) {
-        x86_load_linux(x86ms, fw_cfg, 0, true, false);
+        x86_load_linux(x86ms, fw_cfg, 0, true);
     }
 
     if (mms->option_roms) {
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 7280c02ce3..9b192373c0 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -112,6 +112,7 @@ const size_t pc_compat_7_0_len = 
G_N_ELEMENTS(pc_compat_7_0);
 
 GlobalProperty pc_compat_6_2[] = {
     { "virtio-mem", "unplugged-inaccessible", "off" },
+    { TYPE_X86_MACHINE, "linuxboot-randomness", "off" },
 };
 const size_t pc_compat_6_2_len = G_N_ELEMENTS(pc_compat_6_2);
 
@@ -796,7 +797,7 @@ void xen_load_linux(PCMachineState *pcms)
     rom_set_fw(fw_cfg);
 
     x86_load_linux(x86ms, fw_cfg, pcmc->acpi_data_size,
-                   pcmc->pvh_enabled, pcmc->legacy_no_rng_seed);
+                   pcmc->pvh_enabled);
     for (i = 0; i < nb_option_roms; i++) {
         assert(!strcmp(option_rom[i].name, "linuxboot.bin") ||
                !strcmp(option_rom[i].name, "linuxboot_dma.bin") ||
@@ -1118,7 +1119,7 @@ void pc_memory_init(PCMachineState *pcms,
 
     if (linux_boot) {
         x86_load_linux(x86ms, fw_cfg, pcmc->acpi_data_size,
-                       pcmc->pvh_enabled, pcmc->legacy_no_rng_seed);
+                       pcmc->pvh_enabled);
     }
 
     for (i = 0; i < nb_option_roms; i++) {
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index a5c65c1c35..1526b7e3fd 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -447,10 +447,10 @@ DEFINE_I440FX_MACHINE(v7_1, "pc-i440fx-7.1", NULL,
 static void pc_i440fx_7_0_machine_options(MachineClass *m)
 {
     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
+
     pc_i440fx_7_1_machine_options(m);
     m->alias = NULL;
     m->is_default = false;
-    pcmc->legacy_no_rng_seed = true;
     pcmc->enforce_amd_1tb_hole = false;
     compat_props_add(m->compat_props, hw_compat_7_0, hw_compat_7_0_len);
     compat_props_add(m->compat_props, pc_compat_7_0, pc_compat_7_0_len);
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 3a35193ff7..c5b38edc65 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -384,9 +384,9 @@ DEFINE_Q35_MACHINE(v7_1, "pc-q35-7.1", NULL,
 static void pc_q35_7_0_machine_options(MachineClass *m)
 {
     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
+
     pc_q35_7_1_machine_options(m);
     m->alias = NULL;
-    pcmc->legacy_no_rng_seed = true;
     pcmc->enforce_amd_1tb_hole = false;
     compat_props_add(m->compat_props, hw_compat_7_0, hw_compat_7_0_len);
     compat_props_add(m->compat_props, pc_compat_7_0, pc_compat_7_0_len);
diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 050eedc0c8..8c6450ee07 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -60,6 +60,8 @@
 #include CONFIG_DEVICES
 #include "kvm/kvm_i386.h"
 
+#define RNG_SEED_LENGTH 32
+
 /* Physical Address of PVH entry point read from kernel ELF NOTE */
 static size_t pvh_start_addr;
 
@@ -767,8 +769,7 @@ static bool load_elfboot(const char *kernel_filename,
 void x86_load_linux(X86MachineState *x86ms,
                     FWCfgState *fw_cfg,
                     int acpi_data_size,
-                    bool pvh_enabled,
-                    bool legacy_no_rng_seed)
+                    bool pvh_enabled)
 {
     bool linuxboot_dma_enabled = 
X86_MACHINE_GET_CLASS(x86ms)->fwcfg_dma_enabled;
     uint16_t protocol;
@@ -786,7 +787,6 @@ void x86_load_linux(X86MachineState *x86ms,
     const char *dtb_filename = machine->dtb;
     const char *kernel_cmdline = machine->kernel_cmdline;
     SevKernelLoaderContext sev_load_ctx = {};
-    enum { RNG_SEED_LENGTH = 32 };
 
     /* Align to 16 bytes as a paranoia measure */
     cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
@@ -1076,7 +1076,8 @@ void x86_load_linux(X86MachineState *x86ms,
         load_image_size(dtb_filename, setup_data->data, dtb_size);
     }
 
-    if (!legacy_no_rng_seed) {
+    if (x86ms->linuxboot_randomness != ON_OFF_AUTO_OFF &&
+        (protocol >= 0x209 || x86ms->linuxboot_randomness == ON_OFF_AUTO_ON)) {
         setup_data_offset = QEMU_ALIGN_UP(kernel_size, 16);
         kernel_size = setup_data_offset + sizeof(struct setup_data) + 
RNG_SEED_LENGTH;
         kernel = g_realloc(kernel, kernel_size);
@@ -1237,6 +1238,23 @@ static void x86_machine_set_smm(Object *obj, Visitor *v, 
const char *name,
     visit_type_OnOffAuto(v, name, &x86ms->smm, errp);
 }
 
+static void x86_machine_get_linuxboot_randomness(Object *obj, Visitor *v, 
const char *name,
+                                           void *opaque, Error **errp)
+{
+    X86MachineState *x86ms = X86_MACHINE(obj);
+    OnOffAuto linuxboot_randomness = x86ms->linuxboot_randomness;
+
+    visit_type_OnOffAuto(v, name, &linuxboot_randomness, errp);
+}
+
+static void x86_machine_set_linuxboot_randomness(Object *obj, Visitor *v, 
const char *name,
+                                           void *opaque, Error **errp)
+{
+    X86MachineState *x86ms = X86_MACHINE(obj);
+
+    visit_type_OnOffAuto(v, name, &x86ms->linuxboot_randomness, errp);
+}
+
 bool x86_machine_is_acpi_enabled(const X86MachineState *x86ms)
 {
     if (x86ms->acpi == ON_OFF_AUTO_OFF) {
@@ -1387,6 +1405,7 @@ static void x86_machine_initfn(Object *obj)
     x86ms->acpi = ON_OFF_AUTO_AUTO;
     x86ms->pit = ON_OFF_AUTO_AUTO;
     x86ms->pic = ON_OFF_AUTO_AUTO;
+    x86ms->linuxboot_randomness = ON_OFF_AUTO_AUTO;
     x86ms->pci_irq_mask = ACPI_BUILD_PCI_IRQS;
     x86ms->oem_id = g_strndup(ACPI_BUILD_APPNAME6, 6);
     x86ms->oem_table_id = g_strndup(ACPI_BUILD_APPNAME8, 8);
@@ -1426,6 +1445,12 @@ static void x86_machine_class_init(ObjectClass *oc, void 
*data)
     object_class_property_set_description(oc, X86_MACHINE_PIT,
         "Enable i8254 PIT");
 
+    object_class_property_add(oc, X86_MACHINE_LINUXBOOT_RANDOMNESS, 
"OnOffAuto",
+        x86_machine_get_linuxboot_randomness, 
x86_machine_set_linuxboot_randomness,
+        NULL, NULL);
+    object_class_property_set_description(oc, X86_MACHINE_LINUXBOOT_RANDOMNESS,
+        "Pass random number seed to -kernel Linux image");
+
     object_class_property_add(oc, X86_MACHINE_PIC, "OnOffAuto",
                               x86_machine_get_pic,
                               x86_machine_set_pic,
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 8435733bd6..9cc3f5d338 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -128,9 +128,6 @@ struct PCMachineClass {
 
     /* create kvmclock device even when KVM PV features are not exposed */
     bool kvmclock_create_always;
-
-    /* skip passing an rng seed for legacy machines */
-    bool legacy_no_rng_seed;
 };
 
 #define TYPE_PC_MACHINE "generic-pc-machine"
diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h
index 62fa5774f8..0487c065c8 100644
--- a/include/hw/i386/x86.h
+++ b/include/hw/i386/x86.h
@@ -70,6 +70,7 @@ struct X86MachineState {
     OnOffAuto acpi;
     OnOffAuto pit;
     OnOffAuto pic;
+    OnOffAuto linuxboot_randomness;
 
     char *oem_id;
     char *oem_table_id;
@@ -94,6 +95,7 @@ struct X86MachineState {
 #define X86_MACHINE_OEM_ID           "x-oem-id"
 #define X86_MACHINE_OEM_TABLE_ID     "x-oem-table-id"
 #define X86_MACHINE_BUS_LOCK_RATELIMIT  "bus-lock-ratelimit"
+#define X86_MACHINE_LINUXBOOT_RANDOMNESS "linuxboot-randomness"
 
 #define TYPE_X86_MACHINE   MACHINE_TYPE_NAME("x86")
 OBJECT_DECLARE_TYPE(X86MachineState, X86MachineClass, X86_MACHINE)
@@ -126,8 +128,7 @@ void x86_bios_rom_init(MachineState *ms, const char 
*default_firmware,
 void x86_load_linux(X86MachineState *x86ms,
                     FWCfgState *fw_cfg,
                     int acpi_data_size,
-                    bool pvh_enabled,
-                    bool legacy_no_rng_seed);
+                    bool pvh_enabled);
 
 bool x86_machine_is_smm_enabled(const X86MachineState *x86ms);
 bool x86_machine_is_acpi_enabled(const X86MachineState *x86ms);
-- 
2.37.1