Re: [PATCH 1/1] target/loongarch/kvm: Enable LSX/LASX extension

[gaosong]

在 2024/1/22 下午3:12, maobibo 写道:
> On 2024/1/22 下午2:09, Song Gao wrote:
> > The kernel had already support LSX and LASX [1],
> > but QEMU is disable LSX/LASX for kvm. This patch adds
> > kvm_check_cpucfg to check CPUCFG2.
> >
> > [1]: 
> > https://lore.kernel.org/all/CABgObfZHRf7E_7Jk4uPRmSyxTy3EiuuYwHC35jQncNL9s-zTDA@mail.gmail.com/
> >
> > Signed-off-by: Song Gao <gaosong@loongson.cn>
> > ---
> >   linux-headers/asm-loongarch/kvm.h |  1 +
> >   target/loongarch/kvm/kvm.c        | 35 ++++++++++++++++++++++++-------
> >   2 files changed, 29 insertions(+), 7 deletions(-)
> >
> > diff --git a/linux-headers/asm-loongarch/kvm.h 
> > b/linux-headers/asm-loongarch/kvm.h
> > index c6ad2ee610..923d0bd382 100644
> > --- a/linux-headers/asm-loongarch/kvm.h
> > +++ b/linux-headers/asm-loongarch/kvm.h
> > @@ -79,6 +79,7 @@ struct kvm_fpu {
> >   #define LOONGARCH_REG_64(TYPE, REG)    (TYPE | KVM_REG_SIZE_U64 | 
> > (REG << LOONGARCH_REG_SHIFT))
> >   #define KVM_IOC_CSRID(REG) LOONGARCH_REG_64(KVM_REG_LOONGARCH_CSR, 
> > REG)
> >   #define KVM_IOC_CPUCFG(REG) 
> > LOONGARCH_REG_64(KVM_REG_LOONGARCH_CPUCFG, REG)
> > +#define KVM_LOONGARCH_VCPU_CPUCFG    0
> >     struct kvm_debug_exit_arch {
> >   };
> > diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
> > index 84bcdf5f86..41b6947c7b 100644
> > --- a/target/loongarch/kvm/kvm.c
> > +++ b/target/loongarch/kvm/kvm.c
> > @@ -537,6 +537,28 @@ static int kvm_loongarch_get_cpucfg(CPUState *cs)
> >       return ret;
> >   }
> >   +static int kvm_check_cpucfg(int id, CPUState *cs)
> > +{
> > +    int ret;
> > +    uint64_t val;
> > +    struct kvm_device_attr attr = {
> > +        .group = KVM_LOONGARCH_VCPU_CPUCFG,
> > +        .attr = id,
> > +        .addr = (uint64_t)&val,
> > +    };
> > +    LoongArchCPU *cpu = LOONGARCH_CPU(cs);
> > +    CPULoongArchState *env = &cpu->env;
> > +
> > +    ret = kvm_vcpu_ioctl(cs, KVM_HAS_DEVICE_ATTR, &attr);
> > +
> > +    if (!ret) {
> > +        kvm_vcpu_ioctl(cs, KVM_GET_DEVICE_ATTR, &attr);
> > +        env->cpucfg[id] &= val;
> With feature bit represents supported or disabled, it is ok to use
> logic of qemu feature bitmap and kvm supported feature bitmap.
>
> However about feature version, there will be problem with "and logic".
> Can we use minimal version here?
Yes, we can,  I will correct it on v2.

Thanks.
Song Gao
> Regards
> Bibo Mao
> > +    }
> > +
> > +    return ret;
> > +}
> > +
> >   static int kvm_loongarch_put_cpucfg(CPUState *cs)
> >   {
> >       int i, ret = 0;
> > @@ -545,14 +567,13 @@ static int kvm_loongarch_put_cpucfg(CPUState *cs)
> >       uint64_t val;
> >         for (i = 0; i < 21; i++) {
> > +    if (i == 2) {
> > +            ret = kvm_check_cpucfg(i, cs);
> > +            if (ret) {
> > +                return ret;
> > +            }
> > +    }
> >           val = env->cpucfg[i];
> > -        /* LSX and LASX and LBT are not supported in kvm now */
> > -        if (i == 2) {
> > -            val &= ~(BIT(R_CPUCFG2_LSX_SHIFT) | 
> > BIT(R_CPUCFG2_LASX_SHIFT));
> > -            val &= ~(BIT(R_CPUCFG2_LBT_X86_SHIFT) |
> > -                     BIT(R_CPUCFG2_LBT_ARM_SHIFT) |
> > -                     BIT(R_CPUCFG2_LBT_MIPS_SHIFT));
> > -        }
> >           ret = kvm_set_one_reg(cs, KVM_IOC_CPUCFG(i), &val);
> >           if (ret < 0) {
> >               trace_kvm_failed_put_cpucfg(strerror(errno));