Re: [PATCH RFC 7/7] Revert "hw/i386: pass RNG seed via setup_data entry"

From: Daniel P. Berrangé
Date: Tue Feb 14 2023 - 11:47:30 EST

On Wed, Feb 08, 2023 at 04:12:56PM -0500, Michael S. Tsirkin wrote:
> This reverts commit 67f7e426e53833a5db75b0d813e8d537b8a75bd2.
>
> Fixes: 67f7e426e5 ("hw/i386: pass RNG seed via setup_data entry")
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> include/hw/i386/pc.h | 3 ---
> include/hw/i386/x86.h | 3 +--
> 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 ++++----------------------
> 7 files changed, 8 insertions(+), 34 deletions(-)

All the patches prior to this were clean reverts. This one though
does not look clean, rather it looks like reverting a combination
of 3 commits

commit ffe2d2382e5f1aae1abc4081af407905ef380311
Author: Jason A. Donenfeld <Jason@xxxxxxxxx>
Date: Wed Sep 21 11:31:34 2022 +0200

x86: re-enable rng seeding via SetupData

commit 3824e25db1a84fadc50b88dfbe27047aa2f7f85d
Author: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Date: Wed Aug 17 10:39:40 2022 +0200

x86: disable rng seeding via setup_data

commit 67f7e426e53833a5db75b0d813e8d537b8a75bd2
Author: Jason A. Donenfeld <Jason@xxxxxxxxx>
Date: Thu Jul 21 14:56:36 2022 +0200

hw/i386: pass RNG seed via setup_data entry



though, even taking the individual commits isn't a perfectly
clean revert due to other unrelated changes in machine
type versioning.

I'm not too fussed if this last one isn't a clean revert,
but lets just call out in the commit message that we're
just manually resolving conflicts and skipping those
two intermediate commits for simplicity.

Assuming an improve commit message:

Reviewed-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>



>
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 66e3d059ef..44b08554fa 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -127,9 +127,6 @@ 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..df82c5fd42 100644
> --- a/include/hw/i386/x86.h
> +++ b/include/hw/i386/x86.h
> @@ -126,8 +126,7 @@ 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);
> diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> index 170a331e3f..b231ceda9a 100644
> --- a/hw/i386/microvm.c
> +++ b/hw/i386/microvm.c
> @@ -330,7 +330,7 @@ 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 6e592bd969..2c5f675ba4 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -804,7 +804,7 @@ 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") ||
> @@ -1124,7 +1124,7 @@ 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 df64dd8dcc..839bd65df5 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -476,9 +476,7 @@ DEFINE_I440FX_MACHINE(v7_2, "pc-i440fx-7.2", NULL,
>
> static void pc_i440fx_7_1_machine_options(MachineClass *m)
> {
> - PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> pc_i440fx_7_2_machine_options(m);
> - pcmc->legacy_no_rng_seed = true;
> compat_props_add(m->compat_props, hw_compat_7_1, hw_compat_7_1_len);
> compat_props_add(m->compat_props, pc_compat_7_1, pc_compat_7_1_len);
> }
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index 66cd718b70..e6e3966262 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -395,9 +395,7 @@ DEFINE_Q35_MACHINE(v7_2, "pc-q35-7.2", NULL,
>
> static void pc_q35_7_1_machine_options(MachineClass *m)
> {
> - PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> pc_q35_7_2_machine_options(m);
> - pcmc->legacy_no_rng_seed = true;
> compat_props_add(m->compat_props, hw_compat_7_1, hw_compat_7_1_len);
> compat_props_add(m->compat_props, pc_compat_7_1, pc_compat_7_1_len);
> }
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index 4831193c86..80be3032cc 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -26,7 +26,6 @@
> #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"
> @@ -771,8 +770,7 @@ 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;
> @@ -780,7 +778,7 @@ 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, first_setup_data = 0;
> + hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0;
> FILE *f;
> char *vmode;
> MachineState *machine = MACHINE(x86ms);
> @@ -790,7 +788,6 @@ 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;
> @@ -1070,31 +1067,16 @@ 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 = cpu_to_le64(first_setup_data);
> - first_setup_data = prot_addr + setup_data_offset;
> + setup_data->next = 0;
> 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
> --
> MST
>

With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|