On Tue, Jun 13, 2023 at 4:52 AM Daniel Henrique Barboza <dbarb...@ventanamicro.com> wrote: > > > > On 6/12/23 00:56, Alistair Francis wrote: > > On Wed, May 31, 2023 at 5:49 AM Daniel Henrique Barboza > > <dbarb...@ventanamicro.com> wrote: > >> > >> We're going to change the handling of mvendorid/marchid/mimpid by the > >> KVM driver. Since these are always present in all CPUs let's put the > >> same validation for everyone. > >> > >> It doesn't make sense to allow 'mvendorid' to be different than it > >> is already set in named (vendor) CPUs. Generic (dynamic) CPUs can have > >> any 'mvendorid' they want. > >> > >> Change 'mvendorid' to be a class property created via > >> 'object_class_property_add', instead of using the DEFINE_PROP_UINT32() > >> macro. This allow us to define a custom setter for it that will verify, > >> for named CPUs, if mvendorid is different than it is already set by the > >> CPU. This is the error thrown for the 'veyron-v1' CPU if 'mvendorid' is > >> set to an invalid value: > >> > >> $ qemu-system-riscv64 -M virt -nographic -cpu veyron-v1,mvendorid=2 > >> qemu-system-riscv64: can't apply global veyron-v1-riscv-cpu.mvendorid=2: > >> Unable to change veyron-v1-riscv-cpu mvendorid (0x61f) > > > > Is this something we want to enforce? What if someone wanted to test > > using the veyron-v1 CPU but they wanted to change some properties. I > > don't see an advantage in not letting them do that > > The idea is to keep things simpler for us. As it is today we forbid users to > enable/disable extensions for vendor CPUs. Doing the same thing for > mvendorid/marchid/mimpid seems consistent with what we're already doing. > > Also, guest software might rely on vendor IDs from the CPU to take certain > actions, and if the user is free to change the CPU ID from vendor CPUs the > software will misbehave and the user can claim "I created a veyron-v1 CPU and > the guest it's like like it's not". Allowing mvendorid and friends to be > changed > doesn't do much for users (we forbid enabling/disabling extensions, so what's > to gain from changing machine IDs?) and it can be a potential source of bugs.
Fair points. Ok, fine with me then :) Alistair > > > > Thanks, > > > Daniel > > > > > > Alistair > > > >> > >> Signed-off-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com> > >> --- > >> target/riscv/cpu.c | 31 ++++++++++++++++++++++++++++++- > >> 1 file changed, 30 insertions(+), 1 deletion(-) > >> > >> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c > >> index 72f5433776..bcd69bb032 100644 > >> --- a/target/riscv/cpu.c > >> +++ b/target/riscv/cpu.c > >> @@ -1723,7 +1723,6 @@ static void riscv_cpu_add_user_properties(Object > >> *obj) > >> static Property riscv_cpu_properties[] = { > >> DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true), > >> > >> - DEFINE_PROP_UINT32("mvendorid", RISCVCPU, cfg.mvendorid, 0), > >> DEFINE_PROP_UINT64("marchid", RISCVCPU, cfg.marchid, > >> RISCV_CPU_MARCHID), > >> DEFINE_PROP_UINT64("mimpid", RISCVCPU, cfg.mimpid, RISCV_CPU_MIMPID), > >> > >> @@ -1810,6 +1809,32 @@ static const struct TCGCPUOps riscv_tcg_ops = { > >> #endif /* !CONFIG_USER_ONLY */ > >> }; > >> > >> +static bool riscv_cpu_is_dynamic(Object *cpu_obj) > >> +{ > >> + return object_dynamic_cast(cpu_obj, TYPE_RISCV_DYNAMIC_CPU) != NULL; > >> +} > >> + > >> +static void cpu_set_mvendorid(Object *obj, Visitor *v, const char *name, > >> + void *opaque, Error **errp) > >> +{ > >> + bool dynamic_cpu = riscv_cpu_is_dynamic(obj); > >> + RISCVCPU *cpu = RISCV_CPU(obj); > >> + uint32_t prev_val = cpu->cfg.mvendorid; > >> + uint32_t value; > >> + > >> + if (!visit_type_uint32(v, name, &value, errp)) { > >> + return; > >> + } > >> + > >> + if (!dynamic_cpu && prev_val != value) { > >> + error_setg(errp, "Unable to change %s mvendorid (0x%x)", > >> + object_get_typename(obj), prev_val); > >> + return; > >> + } > >> + > >> + cpu->cfg.mvendorid = value; > >> +} > >> + > >> static void riscv_cpu_class_init(ObjectClass *c, void *data) > >> { > >> RISCVCPUClass *mcc = RISCV_CPU_CLASS(c); > >> @@ -1841,6 +1866,10 @@ static void riscv_cpu_class_init(ObjectClass *c, > >> void *data) > >> cc->gdb_get_dynamic_xml = riscv_gdb_get_dynamic_xml; > >> cc->tcg_ops = &riscv_tcg_ops; > >> > >> + object_class_property_add(c, "mvendorid", "uint32", NULL, > >> + cpu_set_mvendorid, > >> + NULL, NULL); > >> + > >> device_class_set_props(dc, riscv_cpu_properties); > >> } > >> > >> -- > >> 2.40.1 > >> > >>