Re: [Qemu-devel] [RFC PATCH 4/4] spapr: Add Hcalls to support PAPR NVDIMM device

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

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On Fri, Feb 15, 2019 at 04:41:10PM +0530, Shivaprasad G Bhat wrote:
> 
> 
> On 02/12/2019 07:58 AM, David Gibson wrote:
> > On Tue, Feb 05, 2019 at 11:26:41PM -0600, Shivaprasad G Bhat wrote:
> > > This patch implements few of the necessary hcalls for the nvdimm support.
> > > 
> > > PAPR semantics is such that each NVDIMM device is comprising of multiple
> > > SCM(Storage Class Memory) blocks. The guest requests the hypervisor to bind
> > > each of the SCM blocks of the NVDIMM device using hcalls. There can be
> > > SCM block unbind requests in case of driver errors or unplug(not supported now)
> > > use cases. The NVDIMM label read/writes are done through hcalls.
> > > 
> > > Since each virtual NVDIMM device is divided into multiple SCM blocks, the bind,
> > > unbind, and queries using hcalls on those blocks can come independently. This
> > > doesn't fit well into the qemu device semantics, where the map/unmap are done
> > > at the (whole)device/object level granularity. The patch doesnt actually
> > > bind/unbind on hcalls but let it happen at the object_add/del phase itself
> > > instead.
> > > 
> > > The guest kernel makes bind/unbind requests for the virtual NVDIMM device at the
> > > region level granularity. Without interleaving, each virtual NVDIMM device is
> > > presented as separate region. There is no way to configure the virtual NVDIMM
> > > interleaving for the guests today. So, there is no way a partial bind/unbind
> > > request can come for the vNVDIMM in a hcall for a subset of SCM blocks of a
> > > virtual NVDIMM. Hence it is safe to do bind/unbind everything during the
> > > object_add/del.
> > Hrm.  I don't entirely follow the above, but implementing something
> > that doesn't really match the PAPR model seems like it could lead to
> > problems.
> 
> In qemu, the device is mapped at the hotplug stage. However the SCM blocks
> map requests can come later block by block. So, we will have to figure out
> if NVDIMM device model is the right fit here.

I don't really understand what that means.  Is there any documentation
I can get on the PAPR pmem model?

> The interleaving of the NVDIMMs actually can send requests for binding
> different blocks of different devices on demand, and thus have partial
> mapping.
> But, I dont see how interleaving can be supported for Virtual NVDIMMs given
> the existing support is only from firmware interfaces like
> UEFI/BIOS.

Um.. I don't know what you mean by interleaving.

> I chose this approach given virtual NVDIMM interleaving support chances are
> less and so pre-mapping is safe, and we can build on the existing NVDIMM
> model.
> 
> > > The kernel today is not using the hcalls - h_scm_mem_query, h_scm_mem_clear,
> > > h_scm_query_logical_mem_binding and h_scm_query_block_mem_binding. They are just
> > > stubs in this patch.
> > > 
> > > Signed-off-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
> > > ---
> > >   hw/ppc/spapr_hcall.c   |  230 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >   include/hw/ppc/spapr.h |   12 ++-
> > >   2 files changed, 240 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> > > index 17bcaa3822..40553e80d6 100644
> > > --- a/hw/ppc/spapr_hcall.c
> > > +++ b/hw/ppc/spapr_hcall.c
> > > @@ -3,11 +3,13 @@
> > >   #include "sysemu/hw_accel.h"
> > >   #include "sysemu/sysemu.h"
> > >   #include "qemu/log.h"
> > > +#include "qemu/range.h"
> > >   #include "qemu/error-report.h"
> > >   #include "cpu.h"
> > >   #include "exec/exec-all.h"
> > >   #include "helper_regs.h"
> > >   #include "hw/ppc/spapr.h"
> > > +#include "hw/ppc/spapr_drc.h"
> > >   #include "hw/ppc/spapr_cpu_core.h"
> > >   #include "mmu-hash64.h"
> > >   #include "cpu-models.h"
> > > @@ -16,6 +18,7 @@
> > >   #include "hw/ppc/spapr_ovec.h"
> > >   #include "mmu-book3s-v3.h"
> > >   #include "hw/mem/memory-device.h"
> > > +#include "hw/mem/nvdimm.h"
> > >   struct LPCRSyncState {
> > >       target_ulong value;
> > > @@ -1808,6 +1811,222 @@ static target_ulong h_update_dt(PowerPCCPU *cpu, sPAPRMachineState *spapr,
> > >       return H_SUCCESS;
> > >   }
> > > +static target_ulong h_scm_read_metadata(PowerPCCPU *cpu,
> > > +                                        sPAPRMachineState *spapr,
> > > +                                        target_ulong opcode,
> > > +                                        target_ulong *args)
> > > +{
> > > +    uint32_t drc_index = args[0];
> > > +    uint64_t offset = args[1];
> > > +    uint8_t numBytesToRead = args[2];
> > This will truncate the argument to 8 bits _before_ you validate it,
> > which doesn't seem like what you want.
> I'll fix it.
> 
> > > +    sPAPRDRConnector *drc = spapr_drc_by_index(drc_index);
> > > +    NVDIMMDevice *nvdimm = NULL;
> > > +    NVDIMMClass *ddc = NULL;
> > > +
> > > +    if (numBytesToRead != 1 && numBytesToRead != 2 &&
> > > +        numBytesToRead != 4 && numBytesToRead != 8) {
> > > +        return H_P3;
> > > +    }
> > > +
> > > +    if (offset & (numBytesToRead - 1)) {
> > > +        return H_P2;
> > > +    }
> > > +
> > > +    if (drc && spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
> > > +        return H_PARAMETER;
> > > +    }
> > > +
> > > +    nvdimm = NVDIMM(drc->dev);
> > > +    ddc = NVDIMM_GET_CLASS(nvdimm);
> > > +
> > > +    ddc->read_label_data(nvdimm, &args[0], numBytesToRead, offset);
> > Hm.  Is this the only way to access the label data, or is it also
> > mapped into the guest visible address space?  I ask because some of
> > the calculations you made about size+label_size in an earlier patch
> > seemed to suggest it was part of the address space.
> Yes. The label is not mapped to the guest visible address space.
> You are right in pointing that out, its a bug.
> That is not needed as in the same patch I am doing
> QEMU_ALIGN_DOWN(size, SPAPR_MINIMUM_SCM_BLOCK_SIZE) to the
> nvdimm size in spapr_memory_pre_plug().
> 
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > > +
> > > +static target_ulong h_scm_write_metadata(PowerPCCPU *cpu,
> > > +                                         sPAPRMachineState *spapr,
> > > +                                         target_ulong opcode,
> > > +                                         target_ulong *args)
> > > +{
> > > +    uint32_t drc_index = args[0];
> > > +    uint64_t offset = args[1];
> > > +    uint64_t data = args[2];
> > > +    int8_t numBytesToWrite = args[3];
> > > +    sPAPRDRConnector *drc = spapr_drc_by_index(drc_index);
> > > +    NVDIMMDevice *nvdimm = NULL;
> > > +    DeviceState *dev = NULL;
> > > +    NVDIMMClass *ddc = NULL;
> > > +
> > > +    if (numBytesToWrite != 1 && numBytesToWrite != 2 &&
> > > +        numBytesToWrite != 4 && numBytesToWrite != 8) {
> > > +        return H_P4;
> > > +    }
> > > +
> > > +    if (offset & (numBytesToWrite - 1)) {
> > > +        return H_P2;
> > > +    }
> > > +
> > > +    if (drc && spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
> > > +        return H_PARAMETER;
> > > +    }
> > > +
> > > +    dev = drc->dev;
> > > +    nvdimm = NVDIMM(dev);
> > > +    if (offset >= nvdimm->label_size) {
> > > +        return H_P3;
> > > +    }
> > > +
> > > +    ddc = NVDIMM_GET_CLASS(nvdimm);
> > > +
> > > +    ddc->write_label_data(nvdimm, &data, numBytesToWrite, offset);
> > > +
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > > +static target_ulong h_scm_bind_mem(PowerPCCPU *cpu, sPAPRMachineState *spapr,
> > > +                                        target_ulong opcode,
> > > +                                        target_ulong *args)
> > > +{
> > > +    uint32_t drc_index = args[0];
> > > +    uint64_t starting_index = args[1];
> > > +    uint64_t no_of_scm_blocks_to_bind = args[2];
> > > +    uint64_t target_logical_mem_addr = args[3];
> > > +    uint64_t continue_token = args[4];
> > > +    uint64_t size;
> > > +    uint64_t total_no_of_scm_blocks;
> > > +
> > > +    sPAPRDRConnector *drc = spapr_drc_by_index(drc_index);
> > > +    hwaddr addr;
> > > +    DeviceState *dev = NULL;
> > > +    PCDIMMDevice *dimm = NULL;
> > > +    Error *local_err = NULL;
> > > +
> > > +    if (drc && spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
> > > +        return H_PARAMETER;
> > > +    }
> > > +
> > > +    dev = drc->dev;
> > > +    dimm = PC_DIMM(dev);
> > > +
> > > +    size = object_property_get_uint(OBJECT(dimm),
> > > +                                    PC_DIMM_SIZE_PROP, &local_err);
> > > +    if (local_err) {
> > > +        error_report_err(local_err);
> > > +        return H_PARAMETER;
> > This should probably be H_HARDWARE, no?  The error isn't caused by one
> > of the parameters.
> Its not clearly defined, so I chose H_PARAMETER to suggest the drc index
> was probably wrong.
> > > +    }
> > > +
> > > +    total_no_of_scm_blocks = size / SPAPR_MINIMUM_SCM_BLOCK_SIZE;
> > > +
> > > +    if (starting_index > total_no_of_scm_blocks) {
> > > +        return H_P2;
> > > +    }
> > > +
> > > +    if ((starting_index + no_of_scm_blocks_to_bind) >
> > > total_no_of_scm_blocks) {
> > You should probably have a check for integer overflow here as well,
> > just to be thorough.
> Ok
> > > +        return H_P3;
> > > +    }
> > > +
> > > +    /* Currently qemu assigns the address. */
> > > +    if (target_logical_mem_addr != 0xffffffffffffffff) {
> > > +        return H_OVERLAP;
> > > +    }
> > > +
> > > +    /*
> > > +     * Currently continue token should be zero qemu has already bound
> > > +     * everything and this hcall doesnt return H_BUSY.
> > > +     */
> > > +    if (continue_token > 0) {
> > > +        return H_P5;
> > > +    }
> > > +
> > > +    /* NB : Already bound, Return target logical address in R4 */
> > > +    addr = object_property_get_uint(OBJECT(dimm),
> > > +                                    PC_DIMM_ADDR_PROP, &local_err);
> > > +    if (local_err) {
> > > +        error_report_err(local_err);
> > > +        return H_PARAMETER;
> > > +    }
> > > +
> > > +    args[1] = addr;
> > > +
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > > +static target_ulong h_scm_unbind_mem(PowerPCCPU *cpu, sPAPRMachineState *spapr,
> > > +                                        target_ulong opcode,
> > > +                                        target_ulong *args)
> > > +{
> > > +    uint64_t starting_scm_logical_addr = args[0];
> > > +    uint64_t no_of_scm_blocks_to_unbind = args[1];
> > > +    uint64_t size_to_unbind;
> > > +    uint64_t continue_token = args[2];
> > > +    Range as = range_empty;
> > > +    GSList *dimms = NULL;
> > > +    bool valid = false;
> > > +
> > > +    size_to_unbind = no_of_scm_blocks_to_unbind * SPAPR_MINIMUM_SCM_BLOCK_SIZE;
> > > +
> > > +    /* Check if starting_scm_logical_addr is block aligned */
> > > +    if (!QEMU_IS_ALIGNED(starting_scm_logical_addr,
> > > +                         SPAPR_MINIMUM_SCM_BLOCK_SIZE)) {
> > > +        return H_PARAMETER;
> > > +    }
> > > +
> > > +    range_init_nofail(&as, starting_scm_logical_addr, size_to_unbind);
> > > +
> > > +    dimms = nvdimm_get_device_list();
> > > +    for (; dimms; dimms = dimms->next) {
> > > +        NVDIMMDevice *nvdimm = dimms->data;
> > > +        Range tmp;
> > > +        int size = object_property_get_int(OBJECT(nvdimm), PC_DIMM_SIZE_PROP,
> > > +                                           NULL);
> > > +        int addr = object_property_get_int(OBJECT(nvdimm), PC_DIMM_ADDR_PROP,
> > > +                                           NULL);
> > > +        range_init_nofail(&tmp, addr, size);
> > > +
> > > +        if (range_contains_range(&tmp, &as)) {
> > > +            valid = true;
> > > +            break;
> > > +        }
> > > +    }
> > > +
> > > +    if (!valid) {
> > > +        return H_P2;
> > > +    }
> > > +
> > > +    if (continue_token > 0) {
> > > +        return H_P3;
> > > +    }
> > > +
> > > +    /*NB : dont do anything, let object_del take care of this for now. */
> > > +
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > > +static target_ulong h_scm_query_block_mem_binding(PowerPCCPU *cpu,
> > > +                                                  sPAPRMachineState *spapr,
> > > +                                                  target_ulong opcode,
> > > +                                                  target_ulong *args)
> > > +{
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > > +static target_ulong h_scm_query_logical_mem_binding(PowerPCCPU *cpu,
> > > +                                                    sPAPRMachineState *spapr,
> > > +                                                    target_ulong opcode,
> > > +                                                    target_ulong *args)
> > > +{
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > > +static target_ulong h_scm_mem_query(PowerPCCPU *cpu, sPAPRMachineState *spapr,
> > > +                                        target_ulong opcode,
> > > +                                        target_ulong *args)
> > > +{
> > > +    return H_SUCCESS;
> > > +}
> > > +
> > >   static spapr_hcall_fn papr_hypercall_table[(MAX_HCALL_OPCODE / 4) + 1];
> > >   static spapr_hcall_fn kvmppc_hypercall_table[KVMPPC_HCALL_MAX - KVMPPC_HCALL_BASE + 1];
> > > @@ -1907,6 +2126,17 @@ static void hypercall_register_types(void)
> > >       /* qemu/KVM-PPC specific hcalls */
> > >       spapr_register_hypercall(KVMPPC_H_RTAS, h_rtas);
> > > +    /* qemu/scm specific hcalls */
> > > +    spapr_register_hypercall(H_SCM_READ_METADATA, h_scm_read_metadata);
> > > +    spapr_register_hypercall(H_SCM_WRITE_METADATA, h_scm_write_metadata);
> > > +    spapr_register_hypercall(H_SCM_BIND_MEM, h_scm_bind_mem);
> > > +    spapr_register_hypercall(H_SCM_UNBIND_MEM, h_scm_unbind_mem);
> > > +    spapr_register_hypercall(H_SCM_QUERY_BLOCK_MEM_BINDING,
> > > +                             h_scm_query_block_mem_binding);
> > > +    spapr_register_hypercall(H_SCM_QUERY_LOGICAL_MEM_BINDING,
> > > +                             h_scm_query_logical_mem_binding);
> > > +    spapr_register_hypercall(H_SCM_MEM_QUERY, h_scm_mem_query);
> > > +
> > >       /* ibm,client-architecture-support support */
> > >       spapr_register_hypercall(KVMPPC_H_CAS, h_client_architecture_support);
> > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > > index 21a9709afe..28249567f4 100644
> > > --- a/include/hw/ppc/spapr.h
> > > +++ b/include/hw/ppc/spapr.h
> > > @@ -268,6 +268,7 @@ struct sPAPRMachineState {
> > >   #define H_P7              -60
> > >   #define H_P8              -61
> > >   #define H_P9              -62
> > > +#define H_OVERLAP         -68
> > >   #define H_UNSUPPORTED_FLAG -256
> > >   #define H_MULTI_THREADS_ACTIVE -9005
> > > @@ -473,8 +474,15 @@ struct sPAPRMachineState {
> > >   #define H_INT_ESB               0x3C8
> > >   #define H_INT_SYNC              0x3CC
> > >   #define H_INT_RESET             0x3D0
> > > -
> > > -#define MAX_HCALL_OPCODE        H_INT_RESET
> > > +#define H_SCM_READ_METADATA     0x3E4
> > > +#define H_SCM_WRITE_METADATA     0x3E8
> > > +#define H_SCM_BIND_MEM          0x3EC
> > > +#define H_SCM_UNBIND_MEM        0x3F0
> > > +#define H_SCM_QUERY_BLOCK_MEM_BINDING 0x3F4
> > > +#define H_SCM_QUERY_LOGICAL_MEM_BINDING 0x3F8
> > > +#define H_SCM_MEM_QUERY         0x3FC
> > > +
> > > +#define MAX_HCALL_OPCODE        H_SCM_MEM_QUERY
> > >   /* The hcalls above are standardized in PAPR and implemented by pHyp
> > >    * as well.
> > > 
> 

-- 
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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