Re: [Qemu-devel] [PATCH 4/5] target-ppc: Synchronize FPU state with KVM

[Scott Wood]

On 01/22/2013 11:05:00 PM, David Gibson wrote:
> Currently qemu does not get and put the state of the floating point  
> and
> vector registers to KVM.  This is obviously a problem for savevm, as  
> well
> as possibly being problematic for debugging of FP-using guests.
>
> This patch fixes this by using new extensions to the ONE_REG  
> interface to
> synchronize the qemu floating point state with KVM.
>
> Signed-off-by: David Gibson <address@hidden>
> ---
>  target-ppc/kvm.c |  123  
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 123 insertions(+)
>
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index e84b993..7ed76be 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -518,6 +518,125 @@ static void kvm_put_one_spr(CPUState *cs,  
> uint64_t id, int spr)
>      }
>  }
>
> +static void kvm_put_fp(CPUState *cs)
> +{
> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> +    CPUPPCState *env = &cpu->env;
> +    struct kvm_one_reg reg;
> +    int i;
> +    int ret;
> +
> +    if (env->insns_flags & PPC_FLOAT) {
> +        uint64_t fpscr = env->fpscr;
> +        bool vsx = !!(env->insns_flags2 & PPC2_VSX);
> +
> +        reg.id = KVM_REG_PPC_FPSCR;
> +        reg.addr = (uintptr_t)&fpscr;
> +        ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
> +        if (ret < 0) {
> +            fprintf(stderr, "Warning: Unable to set FPSCR to KVM:  
> %s\n",
> +                    strerror(errno));
> +        }
> +        for (i = 0; i < 32; i++) {
> +            uint64_t vsr[2];
> +
> +            vsr[0] = float64_val(env->fpr[i]);
> +            vsr[1] = env->vsr[i];
> +            reg.addr = (uintptr_t) &vsr;
> +            reg.id = vsx ? KVM_REG_PPC_VSR(i) : KVM_REG_PPC_FPR(i);
> +
> +            ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
> +            if (ret < 0) {
> +                fprintf(stderr, "Warning Unable to set %s%d to KVM:  
> %s\n",
> +                        vsx ? "VSR" : "FPR", i, strerror(errno));
> +            }
> +        }
> +    }

I don't see where you check a capability, so users of pre-one-reg KVM  
now get (at least) 33 warning messages every time context gets  
synchronized?

-Scott