From: "Jason A. Donenfeld" <ja...@zx2c4.com> 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.apfelb...@gmail.com> Cc: Paolo Bonzini <pbonz...@redhat.com> Cc: Richard Henderson <richard.hender...@linaro.org> Cc: Eduardo Habkost <edua...@habkost.net> Cc: Peter Maydell <peter.mayd...@linaro.org> Cc: Philippe Mathieu-Daudé <f4...@amsat.org> Cc: Laurent Vivier <laur...@vivier.eu> Reviewed-by: Michael S. Tsirkin <m...@redhat.com> Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com> Message-Id: <20220721125636.446842-1-ja...@zx2c4.com> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- hw/i386/microvm.c | 2 +- hw/i386/pc.c | 4 +-- hw/i386/pc_piix.c | 2 ++ hw/i386/pc_q35.c | 2 ++ hw/i386/x86.c | 26 +++++++++++++++++--- include/hw/i386/pc.h | 3 +++ include/hw/i386/x86.h | 3 ++- include/standard-headers/asm-x86/bootparam.h | 1 + 8 files changed, 35 insertions(+), 8 deletions(-) diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c index dc929727dc..7fe8cce03e 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 774cb2bf07..d2b5823ffb 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 a234989ac3..fbf9465318 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 f96cbd04e2..12cc76aaf8 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 6003b4b2df..ecea25d249 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 b7735dccfc..2a8ffbcfa8 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 9089bdd99c..6bdf1f6ab2 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 072e2ed546..b2aaad10e5 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) -- 2.36.1
