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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>
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parent
c287941a4d
commit
67f7e426e5
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@ -332,7 +332,7 @@ static void microvm_memory_init(MicrovmMachineState *mms)
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rom_set_fw(fw_cfg);
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if (machine->kernel_filename != NULL) {
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x86_load_linux(x86ms, fw_cfg, 0, true);
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x86_load_linux(x86ms, fw_cfg, 0, true, false);
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}
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if (mms->option_roms) {
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@ -796,7 +796,7 @@ void xen_load_linux(PCMachineState *pcms)
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rom_set_fw(fw_cfg);
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x86_load_linux(x86ms, fw_cfg, pcmc->acpi_data_size,
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pcmc->pvh_enabled);
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pcmc->pvh_enabled, pcmc->legacy_no_rng_seed);
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for (i = 0; i < nb_option_roms; i++) {
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assert(!strcmp(option_rom[i].name, "linuxboot.bin") ||
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!strcmp(option_rom[i].name, "linuxboot_dma.bin") ||
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@ -992,7 +992,7 @@ void pc_memory_init(PCMachineState *pcms,
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if (linux_boot) {
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x86_load_linux(x86ms, fw_cfg, pcmc->acpi_data_size,
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pcmc->pvh_enabled);
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pcmc->pvh_enabled, pcmc->legacy_no_rng_seed);
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}
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for (i = 0; i < nb_option_roms; i++) {
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@ -438,9 +438,11 @@ DEFINE_I440FX_MACHINE(v7_1, "pc-i440fx-7.1", NULL,
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static void pc_i440fx_7_0_machine_options(MachineClass *m)
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{
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PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
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pc_i440fx_7_1_machine_options(m);
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m->alias = NULL;
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m->is_default = false;
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pcmc->legacy_no_rng_seed = true;
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compat_props_add(m->compat_props, hw_compat_7_0, hw_compat_7_0_len);
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compat_props_add(m->compat_props, pc_compat_7_0, pc_compat_7_0_len);
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}
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@ -375,8 +375,10 @@ DEFINE_Q35_MACHINE(v7_1, "pc-q35-7.1", NULL,
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static void pc_q35_7_0_machine_options(MachineClass *m)
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{
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PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
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pc_q35_7_1_machine_options(m);
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m->alias = NULL;
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pcmc->legacy_no_rng_seed = true;
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compat_props_add(m->compat_props, hw_compat_7_0, hw_compat_7_0_len);
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compat_props_add(m->compat_props, pc_compat_7_0, pc_compat_7_0_len);
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}
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@ -26,6 +26,7 @@
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#include "qemu/cutils.h"
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#include "qemu/units.h"
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#include "qemu/datadir.h"
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#include "qemu/guest-random.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qerror.h"
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#include "qapi/qapi-visit-common.h"
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@ -766,7 +767,8 @@ static bool load_elfboot(const char *kernel_filename,
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void x86_load_linux(X86MachineState *x86ms,
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FWCfgState *fw_cfg,
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int acpi_data_size,
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bool pvh_enabled)
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bool pvh_enabled,
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bool legacy_no_rng_seed)
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{
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bool linuxboot_dma_enabled = X86_MACHINE_GET_CLASS(x86ms)->fwcfg_dma_enabled;
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uint16_t protocol;
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@ -774,7 +776,7 @@ void x86_load_linux(X86MachineState *x86ms,
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int dtb_size, setup_data_offset;
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uint32_t initrd_max;
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uint8_t header[8192], *setup, *kernel;
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hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0;
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hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0, first_setup_data = 0;
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FILE *f;
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char *vmode;
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MachineState *machine = MACHINE(x86ms);
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@ -784,6 +786,7 @@ void x86_load_linux(X86MachineState *x86ms,
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const char *dtb_filename = machine->dtb;
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const char *kernel_cmdline = machine->kernel_cmdline;
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SevKernelLoaderContext sev_load_ctx = {};
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enum { RNG_SEED_LENGTH = 32 };
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/* Align to 16 bytes as a paranoia measure */
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cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
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@ -1063,16 +1066,31 @@ void x86_load_linux(X86MachineState *x86ms,
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kernel_size = setup_data_offset + sizeof(struct setup_data) + dtb_size;
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kernel = g_realloc(kernel, kernel_size);
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stq_p(header + 0x250, prot_addr + setup_data_offset);
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setup_data = (struct setup_data *)(kernel + setup_data_offset);
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setup_data->next = 0;
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setup_data->next = cpu_to_le64(first_setup_data);
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first_setup_data = prot_addr + setup_data_offset;
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setup_data->type = cpu_to_le32(SETUP_DTB);
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setup_data->len = cpu_to_le32(dtb_size);
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load_image_size(dtb_filename, setup_data->data, dtb_size);
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}
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if (!legacy_no_rng_seed) {
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setup_data_offset = QEMU_ALIGN_UP(kernel_size, 16);
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kernel_size = setup_data_offset + sizeof(struct setup_data) + RNG_SEED_LENGTH;
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kernel = g_realloc(kernel, kernel_size);
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setup_data = (struct setup_data *)(kernel + setup_data_offset);
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setup_data->next = cpu_to_le64(first_setup_data);
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first_setup_data = prot_addr + setup_data_offset;
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setup_data->type = cpu_to_le32(SETUP_RNG_SEED);
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setup_data->len = cpu_to_le32(RNG_SEED_LENGTH);
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qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH);
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}
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/* Offset 0x250 is a pointer to the first setup_data link. */
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stq_p(header + 0x250, first_setup_data);
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/*
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* If we're starting an encrypted VM, it will be OVMF based, which uses the
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* efi stub for booting and doesn't require any values to be placed in the
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@ -127,6 +127,9 @@ struct PCMachineClass {
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/* create kvmclock device even when KVM PV features are not exposed */
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bool kvmclock_create_always;
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/* skip passing an rng seed for legacy machines */
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bool legacy_no_rng_seed;
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};
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#define TYPE_PC_MACHINE "generic-pc-machine"
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@ -123,7 +123,8 @@ void x86_bios_rom_init(MachineState *ms, const char *default_firmware,
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void x86_load_linux(X86MachineState *x86ms,
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FWCfgState *fw_cfg,
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int acpi_data_size,
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bool pvh_enabled);
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bool pvh_enabled,
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bool legacy_no_rng_seed);
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bool x86_machine_is_smm_enabled(const X86MachineState *x86ms);
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bool x86_machine_is_acpi_enabled(const X86MachineState *x86ms);
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@ -10,6 +10,7 @@
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#define SETUP_EFI 4
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#define SETUP_APPLE_PROPERTIES 5
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#define SETUP_JAILHOUSE 6
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#define SETUP_RNG_SEED 9
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#define SETUP_INDIRECT (1<<31)
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