Re: [PATCH] ppc/spapr: Add support for implement support for H_SCM_HEALTH

[Shivaprasad G Bhat <sbhat@linux.ibm.com>]

Hi Vaibhav,

Some comments inline..

On 3/29/21 9:52 PM, Vaibhav Jain wrote:
> Add support for H_SCM_HEALTH hcall described at [1] for spapr
> nvdimms. This enables guest to detect the 'unarmed' status of a
> specific spapr nvdimm identified by its DRC and if its unarmed, mark
> the region backed by the nvdimm as read-only.
>
> The patch adds h_scm_health() to handle the H_SCM_HEALTH hcall which
> returns two 64-bit bitmaps (health bitmap, health bitmap mask) derived
> from 'struct nvdimm->unarmed' member.
>
> Linux kernel side changes to enable handling of 'unarmed' nvdimms for
> ppc64 are proposed at [2].
>
> References:
> [1] "Hypercall Op-codes (hcalls)"
>      https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst
>
> [2] "powerpc/papr_scm: Mark nvdimm as unarmed if needed during probe"
>      https://lore.kernel.org/linux-nvdimm/20210329113103.476760-1-vaibhav@linux.ibm.com/
>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
>   hw/ppc/spapr_nvdimm.c  | 30 ++++++++++++++++++++++++++++++
>   include/hw/ppc/spapr.h |  4 ++--
>   2 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
> index b46c36917c..e38740036d 100644
> --- a/hw/ppc/spapr_nvdimm.c
> +++ b/hw/ppc/spapr_nvdimm.c
> @@ -31,6 +31,13 @@
>   #include "qemu/range.h"
>   #include "hw/ppc/spapr_numa.h"
>   
> +/* DIMM health bitmap bitmap indicators */
> +/* SCM device is unable to persist memory contents */
> +#define PAPR_PMEM_UNARMED (1ULL << (63 - 0))
> +
> +/* Bits status indicators for health bitmap indicating unarmed dimm */
> +#define PAPR_PMEM_UNARMED_MASK (PAPR_PMEM_UNARMED)
> +
>   bool spapr_nvdimm_validate(HotplugHandler *hotplug_dev, NVDIMMDevice *nvdimm,
>                              uint64_t size, Error **errp)
>   {
> @@ -467,6 +474,28 @@ static target_ulong h_scm_unbind_all(PowerPCCPU *cpu, SpaprMachineState *spapr,
>       return H_SUCCESS;
>   }
>   
> +static target_ulong h_scm_health(PowerPCCPU *cpu, SpaprMachineState *spapr,
> +                                 target_ulong opcode, target_ulong *args)
> +{
> +    uint32_t drc_index = args[0];
> +    SpaprDrc *drc = spapr_drc_by_index(drc_index);
> +    NVDIMMDevice *nvdimm;
> +
> +    if (drc && spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
> +        return H_PARAMETER;
> +    }
> +


Please check if drc->dev is not NULL too. DRCs are created in advance

and drc->dev may not be assigned if the device is not plugged yet.


> +    nvdimm = NVDIMM(drc->dev);
> +
> +    /* Check if the nvdimm is unarmed and send its status via health bitmaps */
> +    args[0] = nvdimm->unarmed ? PAPR_PMEM_UNARMED_MASK : 0;


Please use object_property_get_bool to fetch the unarmed value.


> +
> +    /* health bitmap mask same as the health bitmap */
> +    args[1] = args[0];
> +
> +    return H_SUCCESS;
> +}
> +
>   static void spapr_scm_register_types(void)
>   {

...


Thanks,

Shivaprasad