On Fri, Dec 1, 2023 at 5:00 AM Daniel Henrique Barboza
<dbarb...@ventanamicro.com> wrote:
>
> Linux RISC-V vector documentation (Document/arch/riscv/vector.rst)
> mandates a prctl() in order to allow an userspace thread to use the
> Vector extension from the host.
>
> This is something to be done in realize() time, after init(), when we
> already decided whether we're using RVV or not. We don't have a
> realize() callback for KVM yet, so add kvm_cpu_realize() and enable RVV
> for the thread via PR_RISCV_V_SET_CONTROL.
>
> Signed-off-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>
Alistair
> ---
> target/riscv/kvm/kvm-cpu.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
> index 45b6cf1cfa..273c71baea 100644
> --- a/target/riscv/kvm/kvm-cpu.c
> +++ b/target/riscv/kvm/kvm-cpu.c
> @@ -18,6 +18,7 @@
>
> #include "qemu/osdep.h"
> #include <sys/ioctl.h>
> +#include <sys/prctl.h>
>
> #include <linux/kvm.h>
>
> @@ -47,6 +48,9 @@
> #include "sysemu/runstate.h"
> #include "hw/riscv/numa.h"
>
> +#define PR_RISCV_V_SET_CONTROL 69
> +#define PR_RISCV_V_VSTATE_CTRL_ON 2
> +
> void riscv_kvm_aplic_request(void *opaque, int irq, int level)
> {
> kvm_set_irq(kvm_state, irq, !!level);
> @@ -1481,11 +1485,36 @@ static void kvm_cpu_instance_init(CPUState *cs)
> }
> }
>
> +/*
> + * We'll get here via the following path:
> + *
> + * riscv_cpu_realize()
> + * -> cpu_exec_realizefn()
> + * -> kvm_cpu_realize() (via accel_cpu_common_realize())
> + */
> +static bool kvm_cpu_realize(CPUState *cs, Error **errp)
> +{
> + RISCVCPU *cpu = RISCV_CPU(cs);
> + int ret;
> +
> + if (riscv_has_ext(&cpu->env, RVV)) {
> + ret = prctl(PR_RISCV_V_SET_CONTROL, PR_RISCV_V_VSTATE_CTRL_ON);
> + if (ret) {
> + error_setg(errp, "Error in prctl PR_RISCV_V_SET_CONTROL, code:
> %s",
> + strerrorname_np(errno));
> + return false;
> + }
> + }
> +
> + return true;
> +}
> +
> static void kvm_cpu_accel_class_init(ObjectClass *oc, void *data)
> {
> AccelCPUClass *acc = ACCEL_CPU_CLASS(oc);
>
> acc->cpu_instance_init = kvm_cpu_instance_init;
> + acc->cpu_target_realize = kvm_cpu_realize;
> }
>
> static const TypeInfo kvm_cpu_accel_type_info = {
> --
> 2.41.0
>
>
