From 7313fffb40ea9775b38ff2ce73c4d6b0f43edc2f Mon Sep 17 00:00:00 2001 From: Daniel Henrique Barboza Date: Thu, 6 Jul 2023 07:17:31 -0300 Subject: [PATCH] target/riscv/kvm.c: update KVM MISA bits Our design philosophy with KVM properties can be resumed in two main decisions based on KVM interface availability and what the user wants to do: - if the user disables an extension that the host KVM module doesn't know about (i.e. it doesn't implement the kvm_get_one_reg() interface), keep booting the CPU. This will avoid users having to deal with issues with older KVM versions while disabling features they don't care; - for any other case we're going to error out immediately. If the user wants to enable a feature that KVM doesn't know about this a problem that is worth aborting - the user must know that the feature wasn't enabled in the hart. Likewise, if KVM knows about the extension, the user wants to enable/disable it, and we fail to do it so, that's also a problem we can't shrug it off. In the case of MISA bits we won't even try enabling bits that aren't already available in the host. The ioctl() is so likely to fail that it's not worth trying. This check is already done in the previous patch, in kvm_cpu_set_misa_ext_cfg(), thus we don't need to worry about it now. In kvm_riscv_update_cpu_misa_ext() we'll go through every potential user option and do as follows: - if the user didn't set the property or set to the same value of the host, do nothing; - Disable the given extension in KVM. Error out if anything goes wrong. Signed-off-by: Daniel Henrique Barboza Reviewed-by: Andrew Jones Acked-by: Alistair Francis Message-Id: <20230706101738.460804-14-dbarboza@ventanamicro.com> Signed-off-by: Alistair Francis --- target/riscv/kvm.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c index 8cd08f4396..f64019e87c 100644 --- a/target/riscv/kvm.c +++ b/target/riscv/kvm.c @@ -162,6 +162,41 @@ static void kvm_cpu_set_misa_ext_cfg(Object *obj, Visitor *v, "enabled in the host", misa_ext_cfg->name); } +static void kvm_riscv_update_cpu_misa_ext(RISCVCPU *cpu, CPUState *cs) +{ + CPURISCVState *env = &cpu->env; + uint64_t id, reg; + int i, ret; + + for (i = 0; i < ARRAY_SIZE(kvm_misa_ext_cfgs); i++) { + KVMCPUConfig *misa_cfg = &kvm_misa_ext_cfgs[i]; + target_ulong misa_bit = misa_cfg->offset; + + if (!misa_cfg->user_set) { + continue; + } + + /* If we're here we're going to disable the MISA bit */ + reg = 0; + id = kvm_riscv_reg_id(env, KVM_REG_RISCV_ISA_EXT, + misa_cfg->kvm_reg_id); + ret = kvm_set_one_reg(cs, id, ®); + if (ret != 0) { + /* + * We're not checking for -EINVAL because if the bit is about + * to be disabled, it means that it was already enabled by + * KVM. We determined that by fetching the 'isa' register + * during init() time. Any error at this point is worth + * aborting. + */ + error_report("Unable to set KVM reg %s, error %d", + misa_cfg->name, ret); + exit(EXIT_FAILURE); + } + env->misa_ext &= ~misa_bit; + } +} + static void kvm_riscv_add_cpu_user_properties(Object *cpu_obj) { int i; @@ -632,8 +667,13 @@ int kvm_arch_init_vcpu(CPUState *cs) if (!object_dynamic_cast(OBJECT(cpu), TYPE_RISCV_CPU_HOST)) { ret = kvm_vcpu_set_machine_ids(cpu, cs); + if (ret != 0) { + return ret; + } } + kvm_riscv_update_cpu_misa_ext(cpu, cs); + return ret; }