Re: [Qemu-ppc] [PATCH qemu] ppc/spapr: Receive and store device tree blob from SLOF

[Greg Kurz]

On Mon, 12 Nov 2018 15:12:26 +1100
Alexey Kardashevskiy <address@hidden> wrote:

> On 12/11/2018 05:10, Greg Kurz wrote:
> > Hi Alexey,
> > 
> > Just a few remarks. See below.
> > 
> > On Thu,  8 Nov 2018 12:44:06 +1100
> > Alexey Kardashevskiy <address@hidden> wrote:
> >   
> >> SLOF receives a device tree and updates it with various properties
> >> before switching to the guest kernel and QEMU is not aware of any changes
> >> made by SLOF. Since there is no real RTAS (QEMU implements it), it makes
> >> sense to pass the SLOF final device tree to QEMU to let it implement
> >> RTAS related tasks better, such as PCI host bus adapter hotplug.
> >>
> >> Specifially, now QEMU can find out the actual XICS phandle (for PHB
> >> hotplug) and the RTAS linux,rtas-entry/base properties (for firmware
> >> assisted NMI - FWNMI).
> >>
> >> This stores the initial DT blob in the sPAPR machine and replaces it
> >> in the KVMPPC_H_UPDATE_DT (new private hypercall) handler.
> >>
> >> This adds an @update_dt_enabled machine property to allow backward
> >> migration.
> >>
> >> SLOF already has a hypercall since
> >> https://github.com/aik/SLOF/commit/e6fc84652c9c0073f9183
> >>
> >> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> >> ---
> >>  include/hw/ppc/spapr.h |  7 ++++++-
> >>  hw/ppc/spapr.c         | 29 ++++++++++++++++++++++++++++-
> >>  hw/ppc/spapr_hcall.c   | 32 ++++++++++++++++++++++++++++++++
> >>  hw/ppc/trace-events    |  2 ++
> >>  4 files changed, 68 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> >> index ad4d7cfd97..f5dcaf44cb 100644
> >> --- a/include/hw/ppc/spapr.h
> >> +++ b/include/hw/ppc/spapr.h
> >> @@ -100,6 +100,7 @@ struct sPAPRMachineClass {
> >>  
> >>      /*< public >*/
> >>      bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs 
> >> */
> >> +    bool update_dt_enabled;    /* enable KVMPPC_H_UPDATE_DT */
> >>      bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
> >>      bool pre_2_10_has_unused_icps;
> >>      bool legacy_irq_allocation;
> >> @@ -136,6 +137,9 @@ struct sPAPRMachineState {
> >>      int vrma_adjust;
> >>      ssize_t rtas_size;
> >>      void *rtas_blob;
> >> +    uint32_t fdt_size;
> >> +    uint32_t fdt_initial_size;  
> > 
> > I don't quite see the purpose of fdt_initial_size... it seems to be only
> > used to print a trace.  
> 
> 
> Ah, lost in rebase. The purpose was to test if the new device tree has
> not grown too much.
> 

Ok, makes sense during development.

> 
> 
> >   
> >> +    void *fdt_blob;
> >>      long kernel_size;
> >>      bool kernel_le;
> >>      uint32_t initrd_base;
> >> @@ -462,7 +466,8 @@ struct sPAPRMachineState {
> >>  #define KVMPPC_H_LOGICAL_MEMOP  (KVMPPC_HCALL_BASE + 0x1)
> >>  /* Client Architecture support */
> >>  #define KVMPPC_H_CAS            (KVMPPC_HCALL_BASE + 0x2)
> >> -#define KVMPPC_HCALL_MAX        KVMPPC_H_CAS
> >> +#define KVMPPC_H_UPDATE_DT      (KVMPPC_HCALL_BASE + 0x3)
> >> +#define KVMPPC_HCALL_MAX        KVMPPC_H_UPDATE_DT
> >>  
> >>  typedef struct sPAPRDeviceTreeUpdateHeader {
> >>      uint32_t version_id;
> >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> >> index c08130facb..5e2d4d211c 100644
> >> --- a/hw/ppc/spapr.c
> >> +++ b/hw/ppc/spapr.c
> >> @@ -1633,7 +1633,10 @@ static void spapr_machine_reset(void)
> >>      /* Load the fdt */
> >>      qemu_fdt_dumpdtb(fdt, fdt_totalsize(fdt));
> >>      cpu_physical_memory_write(fdt_addr, fdt, fdt_totalsize(fdt));
> >> -    g_free(fdt);
> >> +    g_free(spapr->fdt_blob);
> >> +    spapr->fdt_size = fdt_totalsize(fdt);
> >> +    spapr->fdt_initial_size = spapr->fdt_size;
> >> +    spapr->fdt_blob = fdt;  
> > 
> > Hmm... It looks weird to store state in a reset handler. I'd rather zeroe
> > both fdt_blob and fdt_size here.  
> 
> 
> The device tree is built from the reset handler and the idea is that we
> want to always have some tree in the machine.
> 

Yes of course, I forgot that we need to keep the fdt to be kept
somewhere so that we can use it :). My remark has more to do
with migration actually: the fdt built at reset time is supposed
to derive from the command line and hot-(un)plugged devices, ie,
identical in source and destination. This isn't state we should
migrate IIUC.

Maybe add a boolean field that tells that the fdt was updated, use
it in spapr_dtb_needed() and reset it in spapr_machine_reset() ?

> 
> 
> >   
> >>  
> >>      /* Set up the entry state */
> >>      spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT, fdt_addr);
> >> @@ -1887,6 +1890,27 @@ static const VMStateDescription 
> >> vmstate_spapr_irq_map = {
> >>      },
> >>  };
> >>  
> >> +static bool spapr_dtb_needed(void *opaque)
> >> +{
> >> +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(opaque);
> >> +
> >> +    return smc->update_dt_enabled;  
> > 
> > This means we always migrate the fdt, even if migration occurs before
> > SLOF could call KVMPPC_H_UPDATE_DT.
> > 
> > With spapr->fdt_blob set to NULL on reset, a better check would be:
> > 
> >     sPAPRMachineState *spapr = SPAPR_MACHINE(opaque);
> > 
> >     return smc->update_dt_enabled && spapr->fdt_blob;
> >   
> >> +}
> >> +
> >> +static const VMStateDescription vmstate_spapr_dtb = {
> >> +    .name = "spapr_dtb",
> >> +    .version_id = 1,
> >> +    .minimum_version_id = 1,
> >> +    .needed = spapr_dtb_needed,
> >> +    .fields = (VMStateField[]) {
> >> +        VMSTATE_UINT32(fdt_initial_size, sPAPRMachineState),
> >> +        VMSTATE_UINT32(fdt_size, sPAPRMachineState),
> >> +        VMSTATE_VBUFFER_ALLOC_UINT32(fdt_blob, sPAPRMachineState, 0, NULL,
> >> +                                     fdt_size),
> >> +        VMSTATE_END_OF_LIST()
> >> +    },
> >> +};
> >> +
> >>  static const VMStateDescription vmstate_spapr = {
> >>      .name = "spapr",
> >>      .version_id = 3,
> >> @@ -1915,6 +1939,7 @@ static const VMStateDescription vmstate_spapr = {
> >>          &vmstate_spapr_cap_sbbc,
> >>          &vmstate_spapr_cap_ibs,
> >>          &vmstate_spapr_irq_map,
> >> +        &vmstate_spapr_dtb,  
> > 
> > This needs to be rebased.
> > 
> > <<<<<<<
> >         &vmstate_spapr_cap_nested_kvm_hv,
> > =======
> >         &vmstate_spapr_dtb,  
> >>>>>>>>  
> > 
> > 
> > I'll try to find some time to respin the PHB hotplug series and I'll happily
> > give a try to this patch.  
> 
> 
> Good :)
> 
> 
> >   
> >>          NULL
> >>      }
> >>  };
> >> @@ -3849,6 +3874,7 @@ static void spapr_machine_class_init(ObjectClass 
> >> *oc, void *data)
> >>      hc->unplug = spapr_machine_device_unplug;
> >>  
> >>      smc->dr_lmb_enabled = true;
> >> +    smc->update_dt_enabled = true;
> >>      mc->default_cpu_type = POWERPC_CPU_TYPE_NAME("power8_v2.0");
> >>      mc->has_hotpluggable_cpus = true;
> >>      smc->resize_hpt_default = SPAPR_RESIZE_HPT_ENABLED;
> >> @@ -3965,6 +3991,7 @@ static void 
> >> spapr_machine_3_0_class_options(MachineClass *mc)
> >>  
> >>      smc->legacy_irq_allocation = true;
> >>      smc->irq = &spapr_irq_xics_legacy;
> >> +    smc->update_dt_enabled = false;
> >>  }
> >>  
> >>  DEFINE_SPAPR_MACHINE(3_0, "3.0", false);
> >> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> >> index ae913d070f..d5833f3f8d 100644
> >> --- a/hw/ppc/spapr_hcall.c
> >> +++ b/hw/ppc/spapr_hcall.c
> >> @@ -1717,6 +1717,36 @@ static target_ulong 
> >> h_get_cpu_characteristics(PowerPCCPU *cpu,
> >>  
> >>      args[0] = characteristics;
> >>      args[1] = behaviour;
> >> +    return H_SUCCESS;
> >> +}
> >> +
> >> +static target_ulong h_update_dt(PowerPCCPU *cpu, sPAPRMachineState *spapr,
> >> +                                target_ulong opcode, target_ulong *args)
> >> +{
> >> +    target_ulong dt = ppc64_phys_to_real(args[0]);
> >> +    struct fdt_header hdr = { 0 };
> >> +    unsigned cb;
> >> +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
> >> +
> >> +    cpu_physical_memory_read(dt, &hdr, sizeof(hdr));
> >> +    cb = fdt32_to_cpu(hdr.totalsize);
> >> +
> >> +    if (fdt_check_full(spapr->fdt_blob, cb)) {
> >> +        trace_spapr_update_dt_failed(spapr->fdt_initial_size, cb,
> >> +            fdt32_to_cpu(hdr.magic));
> >> +        return H_PARAMETER;
> >> +    }
> >> +
> >> +    if (!smc->update_dt_enabled) {
> >> +        return H_SUCCESS;
> >> +    }
> >> +
> >> +    g_free(spapr->fdt_blob);
> >> +    spapr->fdt_size = cb;
> >> +    spapr->fdt_blob = g_malloc0(cb);
> >> +    cpu_physical_memory_read(dt, spapr->fdt_blob, cb);
> >> +
> >> +    trace_spapr_update_dt(cb);
> >>  
> >>      return H_SUCCESS;
> >>  }
> >> @@ -1822,6 +1852,8 @@ static void hypercall_register_types(void)
> >>  
> >>      /* ibm,client-architecture-support support */
> >>      spapr_register_hypercall(KVMPPC_H_CAS, h_client_architecture_support);
> >> +
> >> +    spapr_register_hypercall(KVMPPC_H_UPDATE_DT, h_update_dt);
> >>  }
> >>  
> >>  type_init(hypercall_register_types)
> >> diff --git a/hw/ppc/trace-events b/hw/ppc/trace-events
> >> index dc5e65aee9..4432a5ce74 100644
> >> --- a/hw/ppc/trace-events
> >> +++ b/hw/ppc/trace-events
> >> @@ -22,6 +22,8 @@ spapr_cas_pvr_try(uint32_t pvr) "0x%x"
> >>  spapr_cas_pvr(uint32_t cur_pvr, bool explicit_match, uint32_t new_pvr) 
> >> "current=0x%x, explicit_match=%u, new=0x%x"
> >>  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
> >> +spapr_update_dt(unsigned cb) "New blob %u bytes"
> >> +spapr_update_dt_failed(unsigned cbold, unsigned cbnew, unsigned magic) 
> >> "Old blob %u bytes, new blob %u bytes, magic 0x%x"
> >>  
> >>  # hw/ppc/spapr_iommu.c
> >>  spapr_iommu_put(uint64_t liobn, uint64_t ioba, uint64_t tce, uint64_t 
> >> ret) "liobn=0x%"PRIx64" ioba=0x%"PRIx64" tce=0x%"PRIx64" ret=%"PRId64  
> >   
>