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

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Dec 09, 2016 at 11:08:02AM -0600, Michael Roth wrote:
> 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.

resize-hpt=enabled means we'll fall back if the guest doesn't support
it.  An error here means the _host_ can't support it.  I think not
falling back is the better option in this case - if you've explicitly
tried to enable it from it should be available or fail.  In particular
this will make it safer for migrations where the source is already
using hpt resizing.

> > +
> >      /* 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
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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