Re: [PATCH v9 14/20] target/riscv/kvm.c: add multi-letter extension KVM properties

[Alistair Francis]

On Thu, Jul 6, 2023 at 10:47 PM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
>
>
> On 7/6/23 09:14, Andrew Jones wrote:
> > On Thu, Jul 06, 2023 at 07:17:32AM -0300, Daniel Henrique Barboza wrote:
> >> Let's add KVM user properties for the multi-letter extensions that KVM
> >> currently supports: zicbom, zicboz, zihintpause, zbb, ssaia, sstc,
> >> svinval and svpbmt.
> >>
> >> As with MISA extensions, we're using the KVMCPUConfig type to hold
> >> information about the state of each extension. However, multi-letter
> >> extensions have more cases to cover than MISA extensions, so we're
> >> adding an extra 'supported' flag as well. This flag will reflect if a
> >> given extension is supported by KVM, i.e. KVM knows how to handle it.
> >> This is determined during KVM extension discovery in
> >> kvm_riscv_init_multiext_cfg(), where we test for ENOENT errors. Any
> >                                                     ^ EINVAL
>
> Alistair, let me know if you want me to send a v10 with this commit msg fix.

I can make the fix when I apply it

Alistair

>
>
> Thanks,
>
> Daniel
>
> >
> >> other error will cause an abort.
> >>
> >> The use of the 'user_set' is similar to what we already do with MISA
> >> extensions: the flag set only if the user is changing the extension
> >> state.
> >>
> >> The 'supported' flag will be used later on to make an exception for
> >> users that are disabling multi-letter extensions that are unknown to
> >> KVM.
> >>
> >> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> >> ---
> >>   target/riscv/cpu.c |   8 +++
> >>   target/riscv/kvm.c | 119 +++++++++++++++++++++++++++++++++++++++++++++
> >>   2 files changed, 127 insertions(+)
> >>
> >> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> >> index 5c8832a030..31e591a938 100644
> >> --- a/target/riscv/cpu.c
> >> +++ b/target/riscv/cpu.c
> >> @@ -1860,6 +1860,14 @@ static void riscv_cpu_add_user_properties(Object 
> >> *obj)
> >>       riscv_cpu_add_misa_properties(obj);
> >>
> >>       for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {
> >> +#ifndef CONFIG_USER_ONLY
> >> +        if (kvm_enabled()) {
> >> +            /* Check if KVM created the property already */
> >> +            if (object_property_find(obj, prop->name)) {
> >> +                continue;
> >> +            }
> >> +        }
> >> +#endif
> >>           qdev_property_add_static(dev, prop);
> >>       }
> >>
> >> diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c
> >> index 7afd6024e6..2d39ec154f 100644
> >> --- a/target/riscv/kvm.c
> >> +++ b/target/riscv/kvm.c
> >> @@ -113,6 +113,7 @@ typedef struct KVMCPUConfig {
> >>       target_ulong offset;
> >>       int kvm_reg_id;
> >>       bool user_set;
> >> +    bool supported;
> >>   } KVMCPUConfig;
> >>
> >>   #define KVM_MISA_CFG(_bit, _reg_id) \
> >> @@ -197,6 +198,81 @@ static void kvm_riscv_update_cpu_misa_ext(RISCVCPU 
> >> *cpu, CPUState *cs)
> >>       }
> >>   }
> >>
> >> +#define CPUCFG(_prop) offsetof(struct RISCVCPUConfig, _prop)
> >> +
> >> +#define KVM_EXT_CFG(_name, _prop, _reg_id) \
> >> +    {.name = _name, .offset = CPUCFG(_prop), \
> >> +     .kvm_reg_id = _reg_id}
> >> +
> >> +static KVMCPUConfig kvm_multi_ext_cfgs[] = {
> >> +    KVM_EXT_CFG("zicbom", ext_icbom, KVM_RISCV_ISA_EXT_ZICBOM),
> >> +    KVM_EXT_CFG("zicboz", ext_icboz, KVM_RISCV_ISA_EXT_ZICBOZ),
> >> +    KVM_EXT_CFG("zihintpause", ext_zihintpause, 
> >> KVM_RISCV_ISA_EXT_ZIHINTPAUSE),
> >> +    KVM_EXT_CFG("zbb", ext_zbb, KVM_RISCV_ISA_EXT_ZBB),
> >> +    KVM_EXT_CFG("ssaia", ext_ssaia, KVM_RISCV_ISA_EXT_SSAIA),
> >> +    KVM_EXT_CFG("sstc", ext_sstc, KVM_RISCV_ISA_EXT_SSTC),
> >> +    KVM_EXT_CFG("svinval", ext_svinval, KVM_RISCV_ISA_EXT_SVINVAL),
> >> +    KVM_EXT_CFG("svpbmt", ext_svpbmt, KVM_RISCV_ISA_EXT_SVPBMT),
> >> +};
> >> +
> >> +static void kvm_cpu_cfg_set(RISCVCPU *cpu, KVMCPUConfig *multi_ext,
> >> +                            uint32_t val)
> >> +{
> >> +    int cpu_cfg_offset = multi_ext->offset;
> >> +    bool *ext_enabled = (void *)&cpu->cfg + cpu_cfg_offset;
> >> +
> >> +    *ext_enabled = val;
> >> +}
> >> +
> >> +static uint32_t kvm_cpu_cfg_get(RISCVCPU *cpu,
> >> +                                KVMCPUConfig *multi_ext)
> >> +{
> >> +    int cpu_cfg_offset = multi_ext->offset;
> >> +    bool *ext_enabled = (void *)&cpu->cfg + cpu_cfg_offset;
> >> +
> >> +    return *ext_enabled;
> >> +}
> >> +
> >> +static void kvm_cpu_set_multi_ext_cfg(Object *obj, Visitor *v,
> >> +                                      const char *name,
> >> +                                      void *opaque, Error **errp)
> >> +{
> >> +    KVMCPUConfig *multi_ext_cfg = opaque;
> >> +    RISCVCPU *cpu = RISCV_CPU(obj);
> >> +    bool value, host_val;
> >> +
> >> +    if (!visit_type_bool(v, name, &value, errp)) {
> >> +        return;
> >> +    }
> >> +
> >> +    host_val = kvm_cpu_cfg_get(cpu, multi_ext_cfg);
> >> +
> >> +    /*
> >> +     * Ignore if the user is setting the same value
> >> +     * as the host.
> >> +     */
> >> +    if (value == host_val) {
> >> +        return;
> >> +    }
> >> +
> >> +    if (!multi_ext_cfg->supported) {
> >> +        /*
> >> +         * Error out if the user is trying to enable an
> >> +         * extension that KVM doesn't support. Ignore
> >> +         * option otherwise.
> >> +         */
> >> +        if (value) {
> >> +            error_setg(errp, "KVM does not support disabling extension 
> >> %s",
> >> +                       multi_ext_cfg->name);
> >> +        }
> >> +
> >> +        return;
> >> +    }
> >> +
> >> +    multi_ext_cfg->user_set = true;
> >> +    kvm_cpu_cfg_set(cpu, multi_ext_cfg, value);
> >> +}
> >> +
> >>   static void kvm_riscv_add_cpu_user_properties(Object *cpu_obj)
> >>   {
> >>       int i;
> >> @@ -215,6 +291,15 @@ static void kvm_riscv_add_cpu_user_properties(Object 
> >> *cpu_obj)
> >>           object_property_set_description(cpu_obj, misa_cfg->name,
> >>                                           misa_cfg->description);
> >>       }
> >> +
> >> +    for (i = 0; i < ARRAY_SIZE(kvm_multi_ext_cfgs); i++) {
> >> +        KVMCPUConfig *multi_cfg = &kvm_multi_ext_cfgs[i];
> >> +
> >> +        object_property_add(cpu_obj, multi_cfg->name, "bool",
> >> +                            NULL,
> >> +                            kvm_cpu_set_multi_ext_cfg,
> >> +                            NULL, multi_cfg);
> >> +    }
> >>   }
> >>
> >>   static int kvm_riscv_get_regs_core(CPUState *cs)
> >> @@ -530,6 +615,39 @@ static void kvm_riscv_init_misa_ext_mask(RISCVCPU 
> >> *cpu,
> >>       env->misa_ext = env->misa_ext_mask;
> >>   }
> >>
> >> +static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu, KVMScratchCPU 
> >> *kvmcpu)
> >> +{
> >> +    CPURISCVState *env = &cpu->env;
> >> +    uint64_t val;
> >> +    int i, ret;
> >> +
> >> +    for (i = 0; i < ARRAY_SIZE(kvm_multi_ext_cfgs); i++) {
> >> +        KVMCPUConfig *multi_ext_cfg = &kvm_multi_ext_cfgs[i];
> >> +        struct kvm_one_reg reg;
> >> +
> >> +        reg.id = kvm_riscv_reg_id(env, KVM_REG_RISCV_ISA_EXT,
> >> +                                  multi_ext_cfg->kvm_reg_id);
> >> +        reg.addr = (uint64_t)&val;
> >> +        ret = ioctl(kvmcpu->cpufd, KVM_GET_ONE_REG, &reg);
> >> +        if (ret != 0) {
> >> +            if (errno == EINVAL) {
> >> +                /* Silently default to 'false' if KVM does not support 
> >> it. */
> >> +                multi_ext_cfg->supported = false;
> >> +                val = false;
> >> +            } else {
> >> +                error_report("Unable to read ISA_EXT KVM register %s, "
> >> +                             "error %d", multi_ext_cfg->name, ret);
> >> +                kvm_riscv_destroy_scratch_vcpu(kvmcpu);
> >> +                exit(EXIT_FAILURE);
> >> +            }
> >> +        } else {
> >> +            multi_ext_cfg->supported = true;
> >> +        }
> >> +
> >> +        kvm_cpu_cfg_set(cpu, multi_ext_cfg, val);
> >> +    }
> >> +}
> >> +
> >>   void kvm_riscv_init_user_properties(Object *cpu_obj)
> >>   {
> >>       RISCVCPU *cpu = RISCV_CPU(cpu_obj);
> >> @@ -542,6 +660,7 @@ void kvm_riscv_init_user_properties(Object *cpu_obj)
> >>       kvm_riscv_add_cpu_user_properties(cpu_obj);
> >>       kvm_riscv_init_machine_ids(cpu, &kvmcpu);
> >>       kvm_riscv_init_misa_ext_mask(cpu, &kvmcpu);
> >> +    kvm_riscv_init_multiext_cfg(cpu, &kvmcpu);
> >>
> >>       kvm_riscv_destroy_scratch_vcpu(&kvmcpu);
> >>   }
> >> --
> >> 2.41.0
> >>
> >
> > Otherwise,
> >
> > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>