Re: [PATCH RESEND 09/15] ppc: spapr: Implement nested PAPR hcall - H_GUEST_CREATE_VCPU

[Nicholas Piggin]

On Wed Sep 6, 2023 at 2:33 PM AEST, Harsh Prateek Bora wrote:
> This patch implements support for hcall H_GUEST_CREATE_VCPU which is
> used to instantiate a new VCPU for a previously created nested guest.
> The L1 provide the guest-id (returned by L0 during call to
> H_GUEST_CREATE) and an associated unique vcpu-id to refer to this
> instance in future calls. It is assumed that vcpu-ids are being
> allocated in a sequential manner and max vcpu limit is 2048.
>
> Signed-off-by: Michael Neuling <mikey@neuling.org>
> Signed-off-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
> Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> ---
>  hw/ppc/spapr_nested.c         | 110 ++++++++++++++++++++++++++++++++++
>  include/hw/ppc/spapr.h        |   1 +
>  include/hw/ppc/spapr_nested.h |   1 +
>  3 files changed, 112 insertions(+)
>
> diff --git a/hw/ppc/spapr_nested.c b/hw/ppc/spapr_nested.c
> index 09bbbfb341..e7956685af 100644
> --- a/hw/ppc/spapr_nested.c
> +++ b/hw/ppc/spapr_nested.c
> @@ -376,6 +376,47 @@ void spapr_exit_nested(PowerPCCPU *cpu, int excp)
>      address_space_unmap(CPU(cpu)->as, regs, len, len, true);
>  }
>  
> +static
> +SpaprMachineStateNestedGuest *spapr_get_nested_guest(SpaprMachineState 
> *spapr,
> +                                                     target_ulong lpid)
> +{
> +    SpaprMachineStateNestedGuest *guest;
> +
> +    guest = g_hash_table_lookup(spapr->nested.guests, GINT_TO_POINTER(lpid));
> +    return guest;
> +}

Are you namespacing the new API stuff with papr or no? Might be good to
reduce confusion.

> +
> +static bool vcpu_check(SpaprMachineStateNestedGuest *guest,
> +                       target_ulong vcpuid,
> +                       bool inoutbuf)

What's it checking? That the id is valid? Allocated? Enabled?

> +{
> +    struct SpaprMachineStateNestedGuestVcpu *vcpu;
> +
> +    if (vcpuid >= NESTED_GUEST_VCPU_MAX) {
> +        return false;
> +    }
> +
> +    if (!(vcpuid < guest->vcpus)) {
> +        return false;
> +    }
> +
> +    vcpu = &guest->vcpu[vcpuid];
> +    if (!vcpu->enabled) {
> +        return false;
> +    }
> +
> +    if (!inoutbuf) {
> +        return true;
> +    }
> +
> +    /* Check to see if the in/out buffers are registered */
> +    if (vcpu->runbufin.addr && vcpu->runbufout.addr) {
> +        return true;
> +    }
> +
> +    return false;
> +}
> +
>  static target_ulong h_guest_get_capabilities(PowerPCCPU *cpu,
>                                               SpaprMachineState *spapr,
>                                               target_ulong opcode,
> @@ -448,6 +489,11 @@ static void
>  destroy_guest_helper(gpointer value)
>  {
>      struct SpaprMachineStateNestedGuest *guest = value;
> +    int i = 0;

Don't need to set i = 0 twice. A newline would be good though.

> +    for (i = 0; i < guest->vcpus; i++) {
> +        cpu_ppc_tb_free(&guest->vcpu[i].env);
> +    }
> +    g_free(guest->vcpu);
>      g_free(guest);
>  }
>  
> @@ -518,6 +564,69 @@ static target_ulong h_guest_create(PowerPCCPU *cpu,
>      return H_SUCCESS;
>  }
>  
> +static target_ulong h_guest_create_vcpu(PowerPCCPU *cpu,
> +                                        SpaprMachineState *spapr,
> +                                        target_ulong opcode,
> +                                        target_ulong *args)
> +{
> +    CPUPPCState *env = &cpu->env, *l2env;
> +    target_ulong flags = args[0];
> +    target_ulong lpid = args[1];
> +    target_ulong vcpuid = args[2];
> +    SpaprMachineStateNestedGuest *guest;
> +
> +    if (flags) { /* don't handle any flags for now */
> +        return H_UNSUPPORTED_FLAG;
> +    }
> +
> +    guest = spapr_get_nested_guest(spapr, lpid);
> +    if (!guest) {
> +        return H_P2;
> +    }
> +
> +    if (vcpuid < guest->vcpus) {
> +        return H_IN_USE;
> +    }
> +
> +    if (guest->vcpus >= NESTED_GUEST_VCPU_MAX) {
> +        return H_P3;
> +    }
> +
> +    if (guest->vcpus) {
> +        struct SpaprMachineStateNestedGuestVcpu *vcpus;

Ditto for using typedefs. Do a sweep for this.

> +        vcpus = g_try_renew(struct SpaprMachineStateNestedGuestVcpu,
> +                            guest->vcpu,
> +                            guest->vcpus + 1);

g_try_renew doesn't work with NULL mem? That's unfortunate.

> +        if (!vcpus) {
> +            return H_NO_MEM;
> +        }
> +        memset(&vcpus[guest->vcpus], 0,
> +               sizeof(struct SpaprMachineStateNestedGuestVcpu));
> +        guest->vcpu = vcpus;
> +        l2env = &vcpus[guest->vcpus].env;
> +    } else {
> +        guest->vcpu = g_try_new0(struct SpaprMachineStateNestedGuestVcpu, 1);
> +        if (guest->vcpu == NULL) {
> +            return H_NO_MEM;
> +        }
> +        l2env = &guest->vcpu->env;
> +    }

These two legs seem to be doing the same thing in different
ways wrt l2env. Just assign guest->vcpu in the branches and
get the l2env from guest->vcpu[guest->vcpus] afterward, no?

> +    /* need to memset to zero otherwise we leak L1 state to L2 */
> +    memset(l2env, 0, sizeof(CPUPPCState));

AFAIKS you just zeroed it above.

> +    /* Copy L1 PVR to L2 */
> +    l2env->spr[SPR_PVR] = env->spr[SPR_PVR];
> +    cpu_ppc_tb_init(l2env, SPAPR_TIMEBASE_FREQ);

I would move this down to the end, because it's setting up the
vcpu...

> +
> +    guest->vcpus++;
> +    assert(vcpuid < guest->vcpus); /* linear vcpuid allocation only */
> +    guest->vcpu[vcpuid].enabled = true;
> +

... This is still allocating the vcpu so move it up.

> +    if (!vcpu_check(guest, vcpuid, false)) {
> +        return H_PARAMETER;
> +    }
> +    return H_SUCCESS;
> +}
> +
>  void spapr_register_nested(void)
>  {
>      spapr_register_hypercall(KVMPPC_H_SET_PARTITION_TABLE, h_set_ptbl);
> @@ -531,6 +640,7 @@ void spapr_register_nested_phyp(void)
>      spapr_register_hypercall(H_GUEST_GET_CAPABILITIES, 
> h_guest_get_capabilities);
>      spapr_register_hypercall(H_GUEST_SET_CAPABILITIES, 
> h_guest_set_capabilities);
>      spapr_register_hypercall(H_GUEST_CREATE          , h_guest_create);
> +    spapr_register_hypercall(H_GUEST_CREATE_VCPU     , h_guest_create_vcpu);
>  }
>  
>  #else
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 8a6e9ce929..c9f9682a46 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -371,6 +371,7 @@ struct SpaprMachineState {
>  #define H_UNSUPPORTED     -67
>  #define H_OVERLAP         -68
>  #define H_STATE           -75
> +#define H_IN_USE          -77

Why add it here and not in the first patch?

>  #define H_INVALID_ELEMENT_ID               -79
>  #define H_INVALID_ELEMENT_SIZE             -80
>  #define H_INVALID_ELEMENT_VALUE            -81
> diff --git a/include/hw/ppc/spapr_nested.h b/include/hw/ppc/spapr_nested.h
> index 7841027df8..2e8c6ba1ca 100644
> --- a/include/hw/ppc/spapr_nested.h
> +++ b/include/hw/ppc/spapr_nested.h
> @@ -199,6 +199,7 @@
>  
>  /* Nested PAPR API macros */
>  #define NESTED_GUEST_MAX 4096
> +#define NESTED_GUEST_VCPU_MAX 2048
>  

PAPR_ prefix?

>  typedef struct SpaprMachineStateNestedGuest {
>      unsigned long vcpus;