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authorJason A. Donenfeld <Jason@zx2c4.com>2022-07-21 14:56:36 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2022-07-22 19:26:34 +0200
commit67f7e426e53833a5db75b0d813e8d537b8a75bd2 (patch)
tree298a156beaf064924fe109524932123bc0b369eb
parentc287941a4dd5570e4221b0a58590f7231f896e51 (diff)
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hw/i386: pass RNG seed via setup_data entry
Tiny machines optimized for fast boot time generally don't use EFI, which means a random seed has to be supplied some other way. For this purpose, Linux (≥5.20) supports passing a seed in the setup_data table with SETUP_RNG_SEED, specially intended for hypervisors, kexec, and specialized bootloaders. The linked commit shows the upstream kernel implementation. At Paolo's request, we don't pass these to versioned machine types ≤7.0. Link: https://git.kernel.org/tip/tip/c/68b8e9713c8 Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Richard Henderson <richard.henderson@linaro.org> Cc: Eduardo Habkost <eduardo@habkost.net> Cc: Peter Maydell <peter.maydell@linaro.org> Cc: Philippe Mathieu-Daudé <f4bug@amsat.org> Cc: Laurent Vivier <laurent@vivier.eu> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Message-Id: <20220721125636.446842-1-Jason@zx2c4.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--hw/i386/microvm.c2
-rw-r--r--hw/i386/pc.c4
-rw-r--r--hw/i386/pc_piix.c2
-rw-r--r--hw/i386/pc_q35.c2
-rw-r--r--hw/i386/x86.c26
-rw-r--r--include/hw/i386/pc.h3
-rw-r--r--include/hw/i386/x86.h3
-rw-r--r--include/standard-headers/asm-x86/bootparam.h1
8 files changed, 35 insertions, 8 deletions
diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
index dc92972..7fe8cce 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);
+ x86_load_linux(x86ms, fw_cfg, 0, true, false);
}
if (mms->option_roms) {
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 774cb2b..d2b5823 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -796,7 +796,7 @@ 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->pvh_enabled, pcmc->legacy_no_rng_seed);
for (i = 0; i < nb_option_roms; i++) {
assert(!strcmp(option_rom[i].name, "linuxboot.bin") ||
!strcmp(option_rom[i].name, "linuxboot_dma.bin") ||
@@ -992,7 +992,7 @@ void pc_memory_init(PCMachineState *pcms,
if (linux_boot) {
x86_load_linux(x86ms, fw_cfg, pcmc->acpi_data_size,
- pcmc->pvh_enabled);
+ pcmc->pvh_enabled, pcmc->legacy_no_rng_seed);
}
for (i = 0; i < nb_option_roms; i++) {
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index a234989..fbf9465 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -438,9 +438,11 @@ 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;
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 f96cbd0..12cc76a 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -375,8 +375,10 @@ 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;
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 6003b4b..ecea25d 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -26,6 +26,7 @@
#include "qemu/cutils.h"
#include "qemu/units.h"
#include "qemu/datadir.h"
+#include "qemu/guest-random.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qapi/qapi-visit-common.h"
@@ -766,7 +767,8 @@ 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 pvh_enabled,
+ bool legacy_no_rng_seed)
{
bool linuxboot_dma_enabled = X86_MACHINE_GET_CLASS(x86ms)->fwcfg_dma_enabled;
uint16_t protocol;
@@ -774,7 +776,7 @@ void x86_load_linux(X86MachineState *x86ms,
int dtb_size, setup_data_offset;
uint32_t initrd_max;
uint8_t header[8192], *setup, *kernel;
- hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0;
+ hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0, first_setup_data = 0;
FILE *f;
char *vmode;
MachineState *machine = MACHINE(x86ms);
@@ -784,6 +786,7 @@ 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;
@@ -1063,16 +1066,31 @@ void x86_load_linux(X86MachineState *x86ms,
kernel_size = setup_data_offset + sizeof(struct setup_data) + dtb_size;
kernel = g_realloc(kernel, kernel_size);
- stq_p(header + 0x250, prot_addr + setup_data_offset);
setup_data = (struct setup_data *)(kernel + setup_data_offset);
- setup_data->next = 0;
+ setup_data->next = cpu_to_le64(first_setup_data);
+ first_setup_data = prot_addr + setup_data_offset;
setup_data->type = cpu_to_le32(SETUP_DTB);
setup_data->len = cpu_to_le32(dtb_size);
load_image_size(dtb_filename, setup_data->data, dtb_size);
}
+ if (!legacy_no_rng_seed) {
+ 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);
+ setup_data = (struct setup_data *)(kernel + setup_data_offset);
+ setup_data->next = cpu_to_le64(first_setup_data);
+ first_setup_data = prot_addr + setup_data_offset;
+ setup_data->type = cpu_to_le32(SETUP_RNG_SEED);
+ setup_data->len = cpu_to_le32(RNG_SEED_LENGTH);
+ qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH);
+ }
+
+ /* Offset 0x250 is a pointer to the first setup_data link. */
+ stq_p(header + 0x250, first_setup_data);
+
/*
* If we're starting an encrypted VM, it will be OVMF based, which uses the
* efi stub for booting and doesn't require any values to be placed in the
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index b7735dc..2a8ffbc 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -127,6 +127,9 @@ 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 9089bdd..6bdf1f6 100644
--- a/include/hw/i386/x86.h
+++ b/include/hw/i386/x86.h
@@ -123,7 +123,8 @@ 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 pvh_enabled,
+ bool legacy_no_rng_seed);
bool x86_machine_is_smm_enabled(const X86MachineState *x86ms);
bool x86_machine_is_acpi_enabled(const X86MachineState *x86ms);
diff --git a/include/standard-headers/asm-x86/bootparam.h b/include/standard-headers/asm-x86/bootparam.h
index 072e2ed..b2aaad1 100644
--- a/include/standard-headers/asm-x86/bootparam.h
+++ b/include/standard-headers/asm-x86/bootparam.h
@@ -10,6 +10,7 @@
#define SETUP_EFI 4
#define SETUP_APPLE_PROPERTIES 5
#define SETUP_JAILHOUSE 6
+#define SETUP_RNG_SEED 9
#define SETUP_INDIRECT (1<<31)