Re: [Qemu-devel] [PATCH 2/7] ppc: Make kvm_arch_put_registers() put *all* the registers

[Alexander Graf <agraf@suse.de>]

On 08/15/2012 06:33 AM, David Gibson wrote:
> At least when invoked with high enough 'level' arguments,
> kvm_arch_put_registers() is supposed to copy essentially all the cpu state
> as encoded in qemu's internal structures into the kvm state.  Currently
> the ppc version does not do this - it never calls KVM_SET_SREGS, for
> example, and therefore never sets the SDR1 and various other important
> though rarely changed registers.
>
> Instead, the code paths which need to set these registers need to
> explicitly make (conditional) kvm calls which transfer the changes to kvm.
> This breaks the usual model of handling state updates in qemu, where code
> just changes the internal model and has it flushed out to kvm automatically
> at some later point.
>
> This patch fixes this for Book S ppc CPUs by adding a suitable call to
> KVM_SET_SREGS and als to KVM_SET_ONE_REG to set the HIOR (the only register
> that is set with that call so far).  This lets us remove the hacks to
> explicitly set these registers from the kvmppc_set_papr() function.

HIOR is a read-only register from the guest's point of view when running 
in PAPR mode, so we don't need to sync it back again. The same goes for 
SDR1, though resetting that is valid for non-PAPR guests.

Overall, does a normal system reset on PPC guarantee that the SRs and 
SLBs are reset? At least OpenBIOS boots up in real mode and overwrites 
all SR/SLB entries while still in real mode.


Alex

>
> The problem still exists for Book E CPUs (which use a different version of
> the kvm_sregs structure).  But fixing that has some complications of its
> own so can be left to another day.
>
> Lkewise, there is still some ugly code for setting the PVR through special
> calls to SET_SREGS which is left in for now.  The PVR needs to be set
> especially early because it can affect what other features are available
> on the CPU, so I need to do more thinking to see if it can be integrated
> into the normal paths or not.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>   target-ppc/kvm.c |   89 ++++++++++++++++++++++++++++++------------------------
>   1 file changed, 50 insertions(+), 39 deletions(-)
>
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index a31d278..1a7489b 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -60,6 +60,7 @@ static int cap_booke_sregs;
>   static int cap_ppc_smt;
>   static int cap_ppc_rma;
>   static int cap_spapr_tce;
> +static int cap_hior;
>   
>   /* XXX We have a race condition where we actually have a level triggered
>    *     interrupt, but the infrastructure can't expose that yet, so the guest
> @@ -86,6 +87,7 @@ int kvm_arch_init(KVMState *s)
>       cap_ppc_smt = kvm_check_extension(s, KVM_CAP_PPC_SMT);
>       cap_ppc_rma = kvm_check_extension(s, KVM_CAP_PPC_RMA);
>       cap_spapr_tce = kvm_check_extension(s, KVM_CAP_SPAPR_TCE);
> +    cap_hior = kvm_check_extension(s, KVM_CAP_PPC_HIOR);
>   
>       if (!cap_interrupt_level) {
>           fprintf(stderr, "KVM: Couldn't find level irq capability. Expect the "
> @@ -469,6 +471,53 @@ int kvm_arch_put_registers(CPUPPCState *env, int level)
>           env->tlb_dirty = false;
>       }
>   
> +    if (cap_segstate && (level >= KVM_PUT_RESET_STATE)) {
> +        struct kvm_sregs sregs;
> +
> +        sregs.pvr = env->spr[SPR_PVR];
> +
> +        sregs.u.s.sdr1 = env->spr[SPR_SDR1];
> +
> +        /* Sync SLB */
> +#ifdef TARGET_PPC64
> +        for (i = 0; i < 64; i++) {
> +            sregs.u.s.ppc64.slb[i].slbe = env->slb[i].esid;
> +            sregs.u.s.ppc64.slb[i].slbv = env->slb[i].vsid;
> +        }
> +#endif
> +
> +        /* Sync SRs */
> +        for (i = 0; i < 16; i++) {
> +            sregs.u.s.ppc32.sr[i] = env->sr[i];
> +        }
> +
> +        /* Sync BATs */
> +        for (i = 0; i < 8; i++) {
> +            sregs.u.s.ppc32.dbat[i] = ((uint64_t)env->DBAT[1][i] << 32)
> +                | env->DBAT[0][i];
> +            sregs.u.s.ppc32.ibat[i] = ((uint64_t)env->IBAT[1][i] << 32)
> +                | env->IBAT[0][i];
> +        }
> +
> +        ret = kvm_vcpu_ioctl(env, KVM_SET_SREGS, &sregs);
> +        if (ret) {
> +            return ret;
> +        }
> +    }
> +
> +    if (cap_hior && (level >= KVM_PUT_RESET_STATE)) {
> +        uint64_t hior = env->spr[SPR_HIOR];
> +        struct kvm_one_reg reg = {
> +            .id = KVM_REG_PPC_HIOR,
> +            .addr = (uintptr_t) &hior,
> +        };
> +
> +        ret = kvm_vcpu_ioctl(env, KVM_SET_ONE_REG, &reg);
> +        if (ret) {
> +            return ret;
> +        }
> +    }
> +
>       return ret;
>   }
>   
> @@ -946,52 +995,14 @@ int kvmppc_get_hypercall(CPUPPCState *env, uint8_t *buf, int buf_len)
>   void kvmppc_set_papr(CPUPPCState *env)
>   {
>       struct kvm_enable_cap cap = {};
> -    struct kvm_one_reg reg = {};
> -    struct kvm_sregs sregs = {};
>       int ret;
> -    uint64_t hior = env->spr[SPR_HIOR];
>   
>       cap.cap = KVM_CAP_PPC_PAPR;
>       ret = kvm_vcpu_ioctl(env, KVM_ENABLE_CAP, &cap);
>   
>       if (ret) {
> -        goto fail;
> -    }
> -
> -    /*
> -     * XXX We set HIOR here. It really should be a qdev property of
> -     *     the CPU node, but we don't have CPUs converted to qdev yet.
> -     *
> -     *     Once we have qdev CPUs, move HIOR to a qdev property and
> -     *     remove this chunk.
> -     */
> -    reg.id = KVM_REG_PPC_HIOR;
> -    reg.addr = (uintptr_t)&hior;
> -    ret = kvm_vcpu_ioctl(env, KVM_SET_ONE_REG, &reg);
> -    if (ret) {
> -        fprintf(stderr, "Couldn't set HIOR. Maybe you're running an old \n"
> -                        "kernel with support for HV KVM but no PAPR PR \n"
> -                        "KVM in which case things will work. If they don't \n"
> -                        "please update your host kernel!\n");
> -    }
> -
> -    /* Set SDR1 so kernel space finds the HTAB */
> -    ret = kvm_vcpu_ioctl(env, KVM_GET_SREGS, &sregs);
> -    if (ret) {
> -        goto fail;
> -    }
> -
> -    sregs.u.s.sdr1 = env->spr[SPR_SDR1];
> -
> -    ret = kvm_vcpu_ioctl(env, KVM_SET_SREGS, &sregs);
> -    if (ret) {
> -        goto fail;
> +        cpu_abort(env, "This KVM version does not support PAPR\n");
>       }
> -
> -    return;
> -
> -fail:
> -    cpu_abort(env, "This KVM version does not support PAPR\n");
>   }
>   
>   int kvmppc_smt_threads(void)