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From: Oliver <oohall@gmail.com>
Date: Mon, 15 Oct 2018 10:14:42 +1100
Message-ID: <CAOSf1CGYPxW97MoV4dZ20iAydLpPyHhdoxhARL2ECi4YTymbrA@mail.gmail.com>
Subject: Re: [PATCH 2/2] powerpc/pseries: Add driver for PAPR SCM regions
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>, linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
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On Sat, Oct 13, 2018 at 9:37 AM Dan Williams <dan.j.williams@intel.com> wrote:
>
> On Tue, Oct 9, 2018 at 11:21 PM Oliver O'Halloran <oohall@gmail.com> wrote:
> >
> > Adds a driver that implements support for enabling and accessing PAPR
> > SCM regions. Unfortunately due to how the PAPR interface works we can't
> > use the existing of_pmem driver (yet) because:
> >
> >  a) The guest is required to use the H_SCM_BIND_MEM h-call to add
> >     add the SCM region to it's physical address space, and
> >  b) There is currently no mechanism for relating a bare of_pmem region
> >     to the backing DIMM (or not-a-DIMM for our case).
> >
> > Both of these are easily handled by rolling the functionality into a
> > seperate driver so here we are...
> >
> > Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
> > ---
> > The alternative implementation here is that we have the pseries code
> > do the h-calls and craft a pmem-region@<addr> node based on that.
> > However, that doesn't solve b) and mpe has expressed his dislike of
> > adding new stuff to the DT at runtime so i'd say that's a non-starter.
> > ---
> >  arch/powerpc/platforms/pseries/Kconfig    |   7 +
> >  arch/powerpc/platforms/pseries/Makefile   |   1 +
> >  arch/powerpc/platforms/pseries/papr_scm.c | 340 ++++++++++++++++++++++++++++++
> >  3 files changed, 348 insertions(+)
> >  create mode 100644 arch/powerpc/platforms/pseries/papr_scm.c
> >
> > diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
> > index 0c698fd6d491..4b0fcb80efe5 100644
> > --- a/arch/powerpc/platforms/pseries/Kconfig
> > +++ b/arch/powerpc/platforms/pseries/Kconfig
> > @@ -140,3 +140,10 @@ config IBMEBUS
> >         bool "Support for GX bus based adapters"
> >         help
> >           Bus device driver for GX bus based adapters.
> > +
> > +config PAPR_SCM
> > +       depends on PPC_PSERIES && MEMORY_HOTPLUG
> > +       select LIBNVDIMM
> > +       tristate "Support for the PAPR Storage Class Memory interface"
> > +       help
> > +         Enable access to hypervisor provided storage class memory.
> > diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
> > index 892b27ced973..a43ec843c8e2 100644
> > --- a/arch/powerpc/platforms/pseries/Makefile
> > +++ b/arch/powerpc/platforms/pseries/Makefile
> > @@ -24,6 +24,7 @@ obj-$(CONFIG_IO_EVENT_IRQ)    += io_event_irq.o
> >  obj-$(CONFIG_LPARCFG)          += lparcfg.o
> >  obj-$(CONFIG_IBMVIO)           += vio.o
> >  obj-$(CONFIG_IBMEBUS)          += ibmebus.o
> > +obj-$(CONFIG_PAPR_SCM)         += papr_scm.o
> >
> >  ifdef CONFIG_PPC_PSERIES
> >  obj-$(CONFIG_SUSPEND)          += suspend.o
> > diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> > new file mode 100644
> > index 000000000000..87d4dbc18845
> > --- /dev/null
> > +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> > @@ -0,0 +1,340 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#define pr_fmt(fmt)    "papr-scm: " fmt
> > +
> > +#include <linux/of.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/ioport.h>
> > +#include <linux/slab.h>
> > +#include <linux/ndctl.h>
> > +#include <linux/libnvdimm.h>
> > +#include <linux/platform_device.h>
> > +
> > +#include <asm/plpar_wrappers.h>
> > +
> > +#define BIND_ANY_ADDR (~0ul)
> > +
> > +#define PAPR_SCM_DIMM_CMD_MASK \
> > +       ((1ul << ND_CMD_GET_CONFIG_SIZE) | \
> > +        (1ul << ND_CMD_GET_CONFIG_DATA) | \
> > +        (1ul << ND_CMD_SET_CONFIG_DATA))
> > +
> > +struct papr_scm_priv {
> > +       struct platform_device *pdev;
> > +       struct device_node *dn;
> > +       uint32_t drc_index;
> > +       uint64_t blocks;
> > +       uint64_t block_size;
> > +       int metadata_size;
> > +
> > +       uint64_t bound_addr;
> > +
> > +       struct nvdimm_bus_descriptor bus_desc;
> > +       struct nvdimm_bus *bus;
> > +       struct nvdimm *nvdimm;
> > +       struct resource res;
> > +       struct nd_region *region;
> > +       struct nd_interleave_set nd_set;
> > +};
> > +
> > +static int drc_pmem_bind(struct papr_scm_priv *p)
> > +{
> > +       unsigned long ret[PLPAR_HCALL_BUFSIZE];
> > +       uint64_t rc, token;
> > +
> > +       /*
> > +        * When the hypervisor cannot map all the requested memory in a single
> > +        * hcall it returns H_BUSY and we call again with the token until
> > +        * we get H_SUCCESS. Aborting the retry loop before getting H_SUCCESS
> > +        * leave the system in an undefined state, so we wait.
> > +        */
> > +       token = 0;
> > +
> > +       do {
> > +               rc = plpar_hcall(H_SCM_BIND_MEM, ret, p->drc_index, 0,
> > +                               p->blocks, BIND_ANY_ADDR, token);
> > +               token = be64_to_cpu(ret[0]);
>
> Does plpar_hcall sleep? Should there be a cond_resched() here if not?

That's probably a good idea. The implementations I have to test with
never return H_BUSY and I had figured it just indicated that

>
> > +       } while (rc == H_BUSY);
> > +
> > +       if (rc) {
> > +               dev_err(&p->pdev->dev, "bind err: %lld\n", rc);
> > +               return -ENXIO;
> > +       }
> > +
> > +       p->bound_addr = be64_to_cpu(ret[1]);
> > +
> > +       dev_dbg(&p->pdev->dev, "bound drc %x to %pR\n", p->drc_index, &p->res);
> > +
> > +       return 0;
> > +}
> > +
> > +static int drc_pmem_unbind(struct papr_scm_priv *p)
> > +{
> > +       unsigned long ret[PLPAR_HCALL_BUFSIZE];
> > +       uint64_t rc, token;
> > +
> > +       token = 0;
> > +
> > +       /* NB: unbind has the same retry requirements mentioned above */
> > +       do {
> > +               rc = plpar_hcall(H_SCM_UNBIND_MEM, ret, p->drc_index,
> > +                               p->bound_addr, p->blocks, token);
> > +               token = be64_to_cpu(ret);
>
> ...same busy loop comment.
>
> > +       } while (rc == H_BUSY);
> > +
> > +       if (rc)
> > +               dev_err(&p->pdev->dev, "unbind error: %lld\n", rc);
> > +
> > +       return !!rc;
> > +}
> > +
> > +static int papr_scm_meta_get(struct papr_scm_priv *p,
> > +                       struct nd_cmd_get_config_data_hdr *hdr)
> > +{
> > +       unsigned long data[PLPAR_HCALL_BUFSIZE];
> > +       int64_t ret;
> > +
> > +       if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
> > +               return -EINVAL;
> > +
> > +       ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
> > +                       hdr->in_offset, 1);
> > +
> > +       if (ret == H_PARAMETER) /* bad DRC index */
> > +               return -ENODEV;
> > +       if (ret)
> > +               return -EINVAL; /* other invalid parameter */
> > +
> > +       hdr->out_buf[0] = data[0] & 0xff;
> > +
> > +       return 0;
> > +}
> > +
> > +static int papr_scm_meta_set(struct papr_scm_priv *p,
> > +                       struct nd_cmd_set_config_hdr *hdr)
> > +{
> > +       int64_t ret;
> > +
> > +       if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
> > +               return -EINVAL;
> > +
> > +       ret = plpar_hcall_norets(H_SCM_WRITE_METADATA,
> > +                       p->drc_index, hdr->in_offset, hdr->in_buf[0], 1);
> > +
> > +       if (ret == H_PARAMETER) /* bad DRC index */
> > +               return -ENODEV;
> > +       if (ret)
> > +               return -EINVAL; /* other invalid parameter */
> > +
> > +       return 0;
> > +}
> > +
> > +int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
> > +               unsigned int cmd, void *buf, unsigned int buf_len, int *cmd_rc)
> > +{
> > +       struct nd_cmd_get_config_size *get_size_hdr;
> > +       struct papr_scm_priv *p;
> > +
> > +       /* Only dimm-specific calls are supported atm */
> > +       if (!nvdimm)
> > +               return -EINVAL;
> > +
> > +       p = nvdimm_provider_data(nvdimm);
> > +
> > +       switch (cmd) {
> > +       case ND_CMD_GET_CONFIG_SIZE:
> > +               get_size_hdr = buf;
> > +
> > +               get_size_hdr->status = 0;
> > +               get_size_hdr->max_xfer = 1;
> > +               get_size_hdr->config_size = p->metadata_size;
> > +               *cmd_rc = 0;
> > +               break;
> > +
> > +       case ND_CMD_GET_CONFIG_DATA:
> > +               *cmd_rc = papr_scm_meta_get(p, buf);
> > +               break;
> > +
> > +       case ND_CMD_SET_CONFIG_DATA:
> > +               *cmd_rc = papr_scm_meta_set(p, buf);
> > +               break;
> > +
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +
> > +       dev_dbg(&p->pdev->dev, "returned with cmd_rc = %d\n", *cmd_rc);
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct attribute_group *region_attr_groups[] = {
> > +       &nd_region_attribute_group,
> > +       &nd_device_attribute_group,
> > +       &nd_mapping_attribute_group,
> > +       &nd_numa_attribute_group,
> > +       NULL,
> > +};
> > +
> > +static const struct attribute_group *bus_attr_groups[] = {
> > +       &nvdimm_bus_attribute_group,
> > +       NULL,
> > +};
> > +
> > +static const struct attribute_group *papr_scm_dimm_groups[] = {
> > +       &nvdimm_attribute_group,
> > +       &nd_device_attribute_group,
> > +       NULL,
> > +};
> > +
> > +static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
> > +{
> > +       struct device *dev = &p->pdev->dev;
> > +       struct nd_mapping_desc mapping;
> > +       struct nd_region_desc ndr_desc;
> > +       unsigned long dimm_flags;
> > +
> > +       p->bus_desc.ndctl = papr_scm_ndctl;
> > +       p->bus_desc.module = THIS_MODULE;
> > +       p->bus_desc.of_node = p->pdev->dev.of_node;
> > +       p->bus_desc.attr_groups = bus_attr_groups;
> > +       p->bus_desc.provider_name = kstrdup(p->pdev->name, GFP_KERNEL);
> > +
> > +       if (!p->bus_desc.provider_name)
> > +               return -ENOMEM;
> > +
> > +       p->bus = nvdimm_bus_register(NULL, &p->bus_desc);
> > +       if (!p->bus) {
> > +               dev_err(dev, "Error creating nvdimm bus %pOF\n", p->dn);
> > +               return -ENXIO;
> > +       }
> > +
> > +       dimm_flags = 0;
> > +       set_bit(NDD_ALIASING, &dimm_flags);
> > +
> > +       p->nvdimm = nvdimm_create(p->bus, p, papr_scm_dimm_groups,
> > +                               dimm_flags, PAPR_SCM_DIMM_CMD_MASK, 0, NULL);
>
> Looks good, although I'm just about to push out commits that change
> this function signature to take a 'security_ops' pointer. If you need
> a stable branch to base this on, let me know.
>
> > +       if (!p->nvdimm) {
> > +               dev_err(dev, "Error creating DIMM object for %pOF\n", p->dn);
> > +               goto err;
> > +       }
> > +
> > +       /* now add the region */
> > +
> > +       memset(&mapping, 0, sizeof(mapping));
> > +       mapping.nvdimm = p->nvdimm;
> > +       mapping.start = p->res.start;
> > +       mapping.size = p->blocks * p->block_size; // XXX: potential overflow?
>
> Ideally, should be nvdimm relative addresses. Since you have just a
> single DIMM per-region I would expect this to be 0 to
> nvdimm->region_size. That said I don't think anything breaks if you
> make the nvdimm address equal to the system-physical address, just
> wanted to point out the intent. This only matters when you have
> multiple DIMMs per region and need to record the per-DIMM contribution
> in the labels on each DIMM.

bleh

That's what I assumed originally. I wasn't sure so I looked at what
the NFIT driver did and confused myself by assuming the address field
of acpi_nfit_memory_map was an SPA.

>
> Other than that looks ok to me:
>
> Acked-by: Dan Williams <dan.j.williams@intel.com>
>
> ...just the matter of what to do about function signature change.
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