On Wed, Sep 10, 2025 at 05:35:27PM +0800, Xie Bo wrote:
> For KVM mode, the privilege mode should not include M-mode, and the
> initial value should be set to S-mode. Additionally, a following patch
> adds the implementation of putting the vCPU privilege mode to KVM.
> When the vCPU runs for the first time, QEMU will first put the privilege
> state to KVM. If the initial value is set to M-mode, KVM will encounter
> an error.
>
> In addition, this patch introduces the 'mp_state' field to RISC-V
> vCPUs, following the convention used by KVM on x86. The 'mp_state'
> reflects the multiprocessor state of a vCPU, and is used to control
> whether the vCPU is runnable by KVM. Randomly select one CPU as the
> boot CPU.
>
> Signed-off-by: Xie Bo <[email protected]>
> ---
> target/riscv/cpu.c | 17 ++++++++++++++++-
> target/riscv/cpu.h | 2 ++
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 09ded6829a..57b8c421bd 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -38,6 +38,7 @@
> #include "kvm/kvm_riscv.h"
> #include "tcg/tcg-cpu.h"
> #include "tcg/tcg.h"
> +#include "hw/boards.h"
>
> /* RISC-V CPU definitions */
> static const char riscv_single_letter_exts[] = "IEMAFDQCBPVH";
> @@ -1031,18 +1032,32 @@ static void riscv_cpu_reset_hold(Object *obj,
> ResetType type)
> #ifndef CONFIG_USER_ONLY
> uint8_t iprio;
> int i, irq, rdzero;
> + static int boot_cpu_index = -1;
> #endif
> CPUState *cs = CPU(obj);
> RISCVCPU *cpu = RISCV_CPU(cs);
> RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(obj);
> CPURISCVState *env = &cpu->env;
> + MachineState *ms = MACHINE(qdev_get_machine());
>
> if (mcc->parent_phases.hold) {
> mcc->parent_phases.hold(obj, type);
> }
> #ifndef CONFIG_USER_ONLY
> env->misa_mxl = mcc->misa_mxl_max;
> - env->priv = PRV_M;
> + if (kvm_enabled()) {
> + env->priv = PRV_S;
> + } else {
> + env->priv = PRV_M;
> + }
> + if (boot_cpu_index < 0) {
> + boot_cpu_index = g_random_int() % ms->smp.cpus;
I don't think we're obliged to use the same boot cpu on each reset
after initially randomly selecting it. We can randomly select each
time.
Also, we can use g_random_int_range() instead of the mod.
Thanks,
drew
> + }
> + if (cs->cpu_index == boot_cpu_index) {
> + env->mp_state = KVM_MP_STATE_RUNNABLE;
> + } else {
> + env->mp_state = KVM_MP_STATE_STOPPED;
> + }
> env->mstatus &= ~(MSTATUS_MIE | MSTATUS_MPRV);
> if (env->misa_mxl > MXL_RV32) {
> /*
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 51e49e03de..4b1c5bf0e4 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -256,6 +256,8 @@ struct CPUArchState {
> #endif
>
> target_ulong priv;
> + /* Current multiprocessor state of this vCPU. */
> + uint32_t mp_state;
> /* CSRs for execution environment configuration */
> uint64_t menvcfg;
> target_ulong senvcfg;
> --
> 2.43.0
>
