Re: [PATCH 1/1] target/riscv/kvm: fix timebase-frequency when using KVM acceleration

[Andrew Jones]

On Wed, Mar 13, 2024 at 04:13:57PM +0800, Yong-Xuan Wang wrote:
> The timebase-frequency of guest OS should be the same with host
> machine. The timebase-frequency value in DTS should be got from
> hypervisor when using KVM acceleration.
> 
> Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
> ---
>  hw/riscv/virt.c              | 11 +++++++++--
>  target/riscv/kvm/kvm-cpu.c   |  9 +++++++++
>  target/riscv/kvm/kvm_riscv.h | 13 +++++++++++++
>  3 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index a094af97c32a..a7ed7fa13010 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -710,8 +710,15 @@ static void create_fdt_sockets(RISCVVirtState *s, const 
> MemMapEntry *memmap,
>      int socket_count = riscv_socket_count(ms);
>  
>      qemu_fdt_add_subnode(ms->fdt, "/cpus");
> -    qemu_fdt_setprop_cell(ms->fdt, "/cpus", "timebase-frequency",
> -                          RISCV_ACLINT_DEFAULT_TIMEBASE_FREQ);
> +
> +    if (kvm_enabled()) {
> +        qemu_fdt_setprop_cell(ms->fdt, "/cpus", "timebase-frequency",
> +                              kvm_riscv_get_timebase_frequency(first_cpu));
> +    } else {
> +        qemu_fdt_setprop_cell(ms->fdt, "/cpus", "timebase-frequency",
> +                              RISCV_ACLINT_DEFAULT_TIMEBASE_FREQ);
> +    }
> +
>      qemu_fdt_setprop_cell(ms->fdt, "/cpus", "#size-cells", 0x0);
>      qemu_fdt_setprop_cell(ms->fdt, "/cpus", "#address-cells", 0x1);
>      qemu_fdt_add_subnode(ms->fdt, "/cpus/cpu-map");
> diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
> index c7afdb1e81b7..bbb115eaa867 100644
> --- a/target/riscv/kvm/kvm-cpu.c
> +++ b/target/riscv/kvm/kvm-cpu.c
> @@ -739,6 +739,15 @@ static void kvm_riscv_put_regs_timer(CPUState *cs)
>      env->kvm_timer_dirty = false;
>  }
>  
> +uint64_t kvm_riscv_get_timebase_frequency(CPUState *cs)
> +{
> +    uint64_t reg;
> +
> +    KVM_RISCV_GET_TIMER(cs, frequency, reg);
> +
> +    return reg;
> +}
> +
>  static int kvm_riscv_get_regs_vector(CPUState *cs)
>  {
>      RISCVCPU *cpu = RISCV_CPU(cs);
> diff --git a/target/riscv/kvm/kvm_riscv.h b/target/riscv/kvm/kvm_riscv.h
> index 4bd98fddc776..130a4bde0480 100644
> --- a/target/riscv/kvm/kvm_riscv.h
> +++ b/target/riscv/kvm/kvm_riscv.h
> @@ -29,4 +29,17 @@ void riscv_kvm_aplic_request(void *opaque, int irq, int 
> level);
>  int kvm_riscv_sync_mpstate_to_kvm(RISCVCPU *cpu, int state);
>  void riscv_kvm_cpu_finalize_features(RISCVCPU *cpu, Error **errp);
>  
> +#ifdef CONFIG_KVM
> +
> +uint64_t kvm_riscv_get_timebase_frequency(CPUState *cs);
> +
> +#else
> +
> +static inline uint64_t kvm_riscv_get_timebase_frequency(CPUState *cs)
> +{
> +    g_assert_not_reached();
> +}
> +
> +#endif
> +

I think we've decided we don't need stubs like these since kvm_riscv_*
functions should always be called within 'if (kvm_enabled())' blocks (as
you have above), and then we leave it to the compile testing to point
out kvm function calls without kvm_enabled().

>  #endif
> -- 
> 2.17.1
>

Besides dropping the stubs,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Thanks,
drew