On Thu, Jul 21, 2022 at 02:29:37PM +0200, Paolo Bonzini wrote: > 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. > > Link: https://git.kernel.org/tip/tip/c/68b8e9713c8 > Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com> > Message-Id: <20220719115300.104095-1-ja...@zx2c4.com> > [Mostly rewritten to preserve guest ABI, but still starting from Jason's > code. - Paolo] > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > hw/i386/pc.c | 1 + > hw/i386/x86.c | 31 ++++++++++++++++++++ > include/hw/i386/x86.h | 2 ++ > include/standard-headers/asm-x86/bootparam.h | 1 + > 4 files changed, 35 insertions(+) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 774cb2bf07..d456fbb166 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-seed", "off" }, > }; > const size_t pc_compat_6_2_len = G_N_ELEMENTS(pc_compat_6_2); > > diff --git a/hw/i386/x86.c b/hw/i386/x86.c > index 564bf3834b..c5d01e084a 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" > @@ -1088,6 +1089,12 @@ void x86_load_linux(X86MachineState *x86ms, > } > fclose(f); > > + if (x86ms->linuxboot_seed != ON_OFF_AUTO_OFF && > + (data.protocol >= 0x209 || x86ms->linuxboot_seed == ON_OFF_AUTO_ON)) > { > + void *seed = add_setup_data(&data, 32, SETUP_RNG_SEED); > + qemu_guest_getrandom_nofail(seed, 32); > + } > + > /* append dtb to kernel */ > if (dtb_filename) { > dtb_size = get_image_size(dtb_filename); > @@ -1247,6 +1254,23 @@ 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_seed(Object *obj, Visitor *v, const > char *name, > + void *opaque, Error **errp) > +{ > + X86MachineState *x86ms = X86_MACHINE(obj); > + OnOffAuto linuxboot_seed = x86ms->linuxboot_seed; > + > + visit_type_OnOffAuto(v, name, &linuxboot_seed, errp); > +} > + > +static void x86_machine_set_linuxboot_seed(Object *obj, Visitor *v, const > char *name, > + void *opaque, Error **errp) > +{ > + X86MachineState *x86ms = X86_MACHINE(obj); > + > + visit_type_OnOffAuto(v, name, &x86ms->linuxboot_seed, errp); > +} > + > bool x86_machine_is_acpi_enabled(const X86MachineState *x86ms) > { > if (x86ms->acpi == ON_OFF_AUTO_OFF) { > @@ -1397,6 +1421,7 @@ 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_seed = 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); > @@ -1435,6 +1460,12 @@ 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_SEED, "OnOffAuto", > + x86_machine_get_linuxboot_seed, x86_machine_set_linuxboot_seed, > + NULL, NULL); > + object_class_property_set_description(oc, X86_MACHINE_LINUXBOOT_SEED, > + "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/x86.h b/include/hw/i386/x86.h > index 9089bdd99c..edf0f6799e 100644 > --- a/include/hw/i386/x86.h > +++ b/include/hw/i386/x86.h > @@ -67,6 +67,7 @@ struct X86MachineState { > OnOffAuto acpi; > OnOffAuto pit; > OnOffAuto pic; > + OnOffAuto linuxboot_seed; > > char *oem_id; > char *oem_table_id; > @@ -91,6 +92,7 @@ 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_SEED "linuxboot-seed"
I am guessing we should prefix this with "x-" so we don't commit to a user interface. > > #define TYPE_X86_MACHINE MACHINE_TYPE_NAME("x86") > OBJECT_DECLARE_TYPE(X86MachineState, X86MachineClass, X86_MACHINE) > 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