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

[Philippe Mathieu-Daudé]

On 13/3/24 09:56, Andrew Jones wrote:
> 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",

Alternatively:
                     kvm_enabled() ?
                     kvm_riscv_get_timebase_frequency(first_cpu) :


> > -                          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().

Yes please!

> >   #endif
> > --
> > 2.17.1