Re: [Qemu-devel] [for-2.9 2/5] pseries: Stubs for HPT resizing

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting David Gibson (2016-12-08 20:23:11)
> This introduces stub implementations of the H_RESIZE_HPT_PREPARE and
> H_RESIZE_HPT_COMMIT hypercalls which we hope to add in a PAPR
> extension to allow run time resizing of a guest's hash page table.  It
> also adds a new machine property for controlling whether this new
> facility is available, and logic to check that against availability
> with KVM (only supported with KVM PR for now).
> 
> Finally, it adds a new string to the hypertas property in the device
> tree, advertising to the guest the availability of the HPT resizing
> hypercalls.  This is a tentative suggested value, and would need to be
> standardized by PAPR before being merged.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c         | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/ppc/spapr_hcall.c   | 36 +++++++++++++++++++++++++++
>  hw/ppc/trace-events    |  2 ++
>  include/hw/ppc/spapr.h | 11 +++++++++
>  target-ppc/kvm.c       | 26 ++++++++++++++++++++
>  target-ppc/kvm_ppc.h   |  5 ++++
>  6 files changed, 146 insertions(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 0f25e83..ecb0822 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -760,6 +760,11 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr, void *fdt)
>      if (!kvm_enabled() || kvmppc_spapr_use_multitce()) {
>          add_str(hypertas, "hcall-multi-tce");
>      }
> +
> +    if (spapr->resize_hpt != SPAPR_RESIZE_HPT_DISABLED) {
> +        add_str(hypertas, "hcall-hpt-resize");
> +    }
> +
>      _FDT(fdt_setprop(fdt, rtas, "ibm,hypertas-functions",
>                       hypertas->str, hypertas->len));
>      g_string_free(hypertas, TRUE);
> @@ -1839,11 +1844,31 @@ static void ppc_spapr_init(MachineState *machine)
>      long load_limit, fw_size;
>      char *filename;
>      int smt = kvmppc_smt_threads();
> +    Error *resize_hpt_err = NULL;
> 
>      msi_nonbroken = true;
> 
>      QLIST_INIT(&spapr->phbs);
> 
> +    /* Check HPT resizing availability */
> +    kvmppc_check_papr_resize_hpt(&resize_hpt_err);
> +    if (spapr->resize_hpt == SPAPR_RESIZE_HPT_DEFAULT) {
> +        if (resize_hpt_err) {
> +            spapr->resize_hpt = SPAPR_RESIZE_HPT_DISABLED;
> +            error_free(resize_hpt_err);
> +            resize_hpt_err = NULL;
> +        } else {
> +            spapr->resize_hpt = smc->resize_hpt_default;
> +        }
> +    }
> +
> +    assert(spapr->resize_hpt != SPAPR_RESIZE_HPT_DEFAULT);
> +
> +    if ((spapr->resize_hpt != SPAPR_RESIZE_HPT_DISABLED) && resize_hpt_err) {
> +        error_report_err(resize_hpt_err);
> +        exit(1);
> +    }

I'm also a bit confused by this. Aren't semantics that HPT_ENABLED will allow
a fallback to non-resizable HPTs if the feature isn't available (whereas
HPT_REQUIRED won't)? I don't understand how such a fallback can ever be reached
with this check in place.

> +
>      /* Allocate RMA if necessary */
>      rma_alloc_size = kvmppc_alloc_rma(&rma);
> 
> @@ -2236,6 +2261,40 @@ static void spapr_set_modern_hotplug_events(Object *obj, bool value,
>      spapr->use_hotplug_event_source = value;
>  }
> 
> +static char *spapr_get_resize_hpt(Object *obj, Error **errp)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> +
> +    switch (spapr->resize_hpt) {
> +    case SPAPR_RESIZE_HPT_DEFAULT:
> +        return g_strdup("default");
> +    case SPAPR_RESIZE_HPT_DISABLED:
> +        return g_strdup("disabled");
> +    case SPAPR_RESIZE_HPT_ENABLED:
> +        return g_strdup("enabled");
> +    case SPAPR_RESIZE_HPT_REQUIRED:
> +        return g_strdup("required");
> +    }
> +    assert(0);
> +}
> +
> +static void spapr_set_resize_hpt(Object *obj, const char *value, Error **errp)
> +{
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> +
> +    if (strcmp(value, "default") == 0) {
> +        spapr->resize_hpt = SPAPR_RESIZE_HPT_DEFAULT;
> +    } else if (strcmp(value, "disabled") == 0) {
> +        spapr->resize_hpt = SPAPR_RESIZE_HPT_DISABLED;
> +    } else if (strcmp(value, "enabled") == 0) {
> +        spapr->resize_hpt = SPAPR_RESIZE_HPT_ENABLED;
> +    } else if (strcmp(value, "required") == 0) {
> +        spapr->resize_hpt = SPAPR_RESIZE_HPT_REQUIRED;
> +    } else {
> +        error_setg(errp, "Bad value for \"resize-hpt\" property");
> +    }
> +}
> +
>  static void spapr_machine_initfn(Object *obj)
>  {
>      sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> @@ -2256,6 +2315,12 @@ static void spapr_machine_initfn(Object *obj)
>                                      " place of standard EPOW events when possible"
>                                      " (required for memory hot-unplug support)",
>                                      NULL);
> +
> +    object_property_add_str(obj, "resize-hpt",
> +                            spapr_get_resize_hpt, spapr_set_resize_hpt, NULL);
> +    object_property_set_description(obj, "resize-hpt",
> +                                    "Resizing of the Hash Page Table (enabled, disabled, required)",
> +                                    NULL);
>  }
> 
>  static void spapr_machine_finalizefn(Object *obj)
> @@ -2707,6 +2772,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
> 
>      smc->dr_lmb_enabled = true;
>      smc->tcg_default_cpu = "POWER8";
> +    smc->resize_hpt_default = SPAPR_RESIZE_HPT_DISABLED;
>      mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
>      fwc->get_dev_path = spapr_get_fw_dev_path;
>      nc->nmi_monitor_handler = spapr_nmi;
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index fd9f1d4..72a9c4d 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -355,6 +355,38 @@ static target_ulong h_read(PowerPCCPU *cpu, sPAPRMachineState *spapr,
>      return H_SUCCESS;
>  }
> 
> +static target_ulong h_resize_hpt_prepare(PowerPCCPU *cpu,
> +                                         sPAPRMachineState *spapr,
> +                                         target_ulong opcode,
> +                                         target_ulong *args)
> +{
> +    target_ulong flags = args[0];
> +    target_ulong shift = args[1];
> +
> +    if (spapr->resize_hpt == SPAPR_RESIZE_HPT_DISABLED) {
> +        return H_AUTHORITY;
> +    }
> +
> +    trace_spapr_h_resize_hpt_prepare(flags, shift);
> +    return H_HARDWARE;
> +}
> +
> +static target_ulong h_resize_hpt_commit(PowerPCCPU *cpu,
> +                                        sPAPRMachineState *spapr,
> +                                        target_ulong opcode,
> +                                        target_ulong *args)
> +{
> +    target_ulong flags = args[0];
> +    target_ulong shift = args[1];
> +
> +    if (spapr->resize_hpt == SPAPR_RESIZE_HPT_DISABLED) {
> +        return H_AUTHORITY;
> +    }
> +
> +    trace_spapr_h_resize_hpt_commit(flags, shift);
> +    return H_HARDWARE;
> +}
> +
>  static target_ulong h_set_sprg0(PowerPCCPU *cpu, sPAPRMachineState *spapr,
>                                  target_ulong opcode, target_ulong *args)
>  {
> @@ -1134,6 +1166,10 @@ static void hypercall_register_types(void)
>      /* hcall-bulk */
>      spapr_register_hypercall(H_BULK_REMOVE, h_bulk_remove);
> 
> +    /* hcall-hpt-resize */
> +    spapr_register_hypercall(H_RESIZE_HPT_PREPARE, h_resize_hpt_prepare);
> +    spapr_register_hypercall(H_RESIZE_HPT_COMMIT, h_resize_hpt_commit);
> +
>      /* hcall-splpar */
>      spapr_register_hypercall(H_REGISTER_VPA, h_register_vpa);
>      spapr_register_hypercall(H_CEDE, h_cede);
> diff --git a/hw/ppc/trace-events b/hw/ppc/trace-events
> index 2297ead..bf59a8f 100644
> --- a/hw/ppc/trace-events
> +++ b/hw/ppc/trace-events
> @@ -16,6 +16,8 @@ spapr_cas_continue(unsigned long n) "Copy changes to the guest: %ld bytes"
>  # hw/ppc/spapr_hcall.c
>  spapr_cas_pvr_try(uint32_t pvr) "%x"
>  spapr_cas_pvr(uint32_t cur_pvr, bool cpu_match, uint32_t new_pvr, uint64_t pcr) "current=%x, cpu_match=%u, new=%x, compat flags=%"PRIx64
> +spapr_h_resize_hpt_prepare(uint64_t flags, uint64_t shift) "flags=0x%"PRIx64", shift=%"PRIu64
> +spapr_h_resize_hpt_commit(uint64_t flags, uint64_t shift) "flags=0x%"PRIx64", shift=%"PRIu64
> 
>  # hw/ppc/spapr_iommu.c
>  spapr_iommu_put(uint64_t liobn, uint64_t ioba, uint64_t tce, uint64_t ret) "liobn=%"PRIx64" ioba=0x%"PRIx64" tce=0x%"PRIx64" ret=%"PRId64
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index a2d8964..d2c758b 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -31,6 +31,13 @@ typedef struct sPAPRMachineState sPAPRMachineState;
>  #define SPAPR_MACHINE_CLASS(klass) \
>      OBJECT_CLASS_CHECK(sPAPRMachineClass, klass, TYPE_SPAPR_MACHINE)
> 
> +typedef enum {
> +    SPAPR_RESIZE_HPT_DEFAULT = 0,
> +    SPAPR_RESIZE_HPT_DISABLED,
> +    SPAPR_RESIZE_HPT_ENABLED,
> +    SPAPR_RESIZE_HPT_REQUIRED,
> +} sPAPRResizeHPT;
> +
>  /**
>   * sPAPRMachineClass:
>   */
> @@ -46,6 +53,7 @@ struct sPAPRMachineClass {
>                            uint64_t *buid, hwaddr *pio, 
>                            hwaddr *mmio32, hwaddr *mmio64,
>                            unsigned n_dma, uint32_t *liobns, Error **errp);
> +    sPAPRResizeHPT resize_hpt_default;
>  };
> 
>  /**
> @@ -61,6 +69,7 @@ struct sPAPRMachineState {
>      XICSState *xics;
>      DeviceState *rtc;
> 
> +    sPAPRResizeHPT resize_hpt;
>      void *htab;
>      uint32_t htab_shift;
>      hwaddr rma_size;
> @@ -347,6 +356,8 @@ struct sPAPRMachineState {
>  #define H_XIRR_X                0x2FC
>  #define H_RANDOM                0x300
>  #define H_SET_MODE              0x31C
> +#define H_RESIZE_HPT_PREPARE    0x36C
> +#define H_RESIZE_HPT_COMMIT     0x370
>  #define H_SIGNAL_SYS_RESET      0x380
>  #define MAX_HCALL_OPCODE        H_SIGNAL_SYS_RESET
> 
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 15e12f3..dcd8cef 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -22,6 +22,7 @@
>  #include <linux/kvm.h>
> 
>  #include "qemu-common.h"
> +#include "qapi/error.h"
>  #include "qemu/error-report.h"
>  #include "cpu.h"
>  #include "qemu/timer.h"
> @@ -2269,6 +2270,7 @@ int kvmppc_reset_htab(int shift_hint)
>          /* Full emulation, tell caller to allocate htab itself */
>          return 0;
>      }
> +
>      if (kvm_check_extension(kvm_state, KVM_CAP_PPC_ALLOC_HTAB)) {
>          int ret;
>          ret = kvm_vm_ioctl(kvm_state, KVM_PPC_ALLOCATE_HTAB, &shift);
> @@ -2672,3 +2674,27 @@ int kvmppc_enable_hwrng(void)
> 
>      return kvmppc_enable_hcall(kvm_state, H_RANDOM);
>  }
> +
> +void kvmppc_check_papr_resize_hpt(Error **errp)
> +{
> +    if (!kvm_enabled()) {
> +        return;
> +    }
> +
> +    /* TODO: Check specific capabilities for HPT resize aware host kernels */
> +
> +    /*
> +     * It's tempting to try to check directly if the HPT is under our
> +     * control or KVM's, which is what's really relevant here.
> +     * Unfortunately, in order to correctly size the HPT, we need to
> +     * know if we can do resizing, _before_ we attempt to allocate it
> +     * with KVM.  Before that point, we don't officially know whether
> +     * we'll control the HPT or not.  So we have to use a fallback
> +     * test for PR vs HV KVM to predict that.
> +     */
> +    if (kvmppc_is_pr(kvm_state)) {
> +        return;
> +    }
> +
> +    error_setg(errp, "Hash page table resizing not available with this KVM version");
> +}
> diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
> index 841a29b..3e852ba 100644
> --- a/target-ppc/kvm_ppc.h
> +++ b/target-ppc/kvm_ppc.h
> @@ -59,6 +59,7 @@ bool kvmppc_has_cap_htm(void);
>  int kvmppc_enable_hwrng(void);
>  int kvmppc_put_books_sregs(PowerPCCPU *cpu);
>  PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void);
> +void kvmppc_check_papr_resize_hpt(Error **errp);
> 
>  #else
> 
> @@ -270,6 +271,10 @@ static inline PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void)
>      return NULL;
>  }
> 
> +static inline void kvmppc_check_papr_resize_hpt(Error **errp)
> +{
> +    return;
> +}
>  #endif
> 
>  #ifndef CONFIG_KVM
> -- 
> 2.9.3
>