Thanks for looking into this patch Greg. My responses below inline. Greg Kurz <groug@xxxxxxxx> writes: > Hi Vaibhav, > > Great to see you around :-) :-) > > On Mon, 29 Mar 2021 21:52:59 +0530 > Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> 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. >> > > Any chance that you can provide the documentation of this new hcall ? > H_SCM_HEALTH specifications is already documented in linux kernel documentation at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst That documentation was added when kernel support for H_SCM_HEALTH hcall support was implemented in 5.9 kernel. >> 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@xxxxxxxxxxxxx/ >> >> Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> >> --- >> 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)) > > This looks like PPC_BIT(0). > Yes, right. Will update the patch in v2 to use the PPC_BIT macro. >> + >> +/* 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; >> + } >> + >> + nvdimm = NVDIMM(drc->dev); > > Yeah as already suggested by Shiva, drc->dev should be checked like > in h_scm_bind_mem(). > Yes, will send a v2 with this case handled. >> + >> + /* Check if the nvdimm is unarmed and send its status via health bitmaps */ >> + args[0] = nvdimm->unarmed ? PAPR_PMEM_UNARMED_MASK : 0; >> + > > Shouldn't ^^ use PAPR_PMEM_UNARMED then ? > >> + /* health bitmap mask same as the health bitmap */ >> + args[1] = args[0]; >> + > > If so, it seems that PAPR_PMEM_UNARMED_MASK isn't even needed. Definition of these defines are similar to what kernel implementation uses at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/platforms/pseries/papr_scm.c#n53 Since unarmed condition can also arise due to an unhealthy nvdimm hence the kernel implementation uses a mask thats composed of two bits PPC_BIT(0) and PPC_BIT(6) being set. Though we arent using PPC_BIT(6) right now in qemu, it will change in future when better nvdimm health reporting will be done. Hence kept the PPC_BIT(0) define as well as the mask to mimic the kernel definitions. > > Having access to the excerpts from the PAPR addendum that describes > this hcall would _really_ help in reviewing. > The kernel documentation for H_SCM_HEALTH mentioned above captures most if not all parts of the PAPR addendum for this hcall. I believe it contains enough information to review the patch. If you still need more info than please let me know. >> + return H_SUCCESS; >> +} >> + >> static void spapr_scm_register_types(void) >> { >> /* qemu/scm specific hcalls */ >> @@ -475,6 +504,7 @@ static void spapr_scm_register_types(void) >> 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_UNBIND_ALL, h_scm_unbind_all); >> + spapr_register_hypercall(H_SCM_HEALTH, h_scm_health); >> } >> >> type_init(spapr_scm_register_types) >> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h >> index 47cebaf3ac..18859b9ab2 100644 >> --- a/include/hw/ppc/spapr.h >> +++ b/include/hw/ppc/spapr.h >> @@ -538,8 +538,8 @@ struct SpaprMachineState { >> #define H_SCM_BIND_MEM 0x3EC >> #define H_SCM_UNBIND_MEM 0x3F0 >> #define H_SCM_UNBIND_ALL 0x3FC >> - >> -#define MAX_HCALL_OPCODE H_SCM_UNBIND_ALL >> +#define H_SCM_HEALTH 0x400 >> +#define MAX_HCALL_OPCODE H_SCM_HEALTH >> >> /* The hcalls above are standardized in PAPR and implemented by pHyp >> * as well. > -- Cheers ~ Vaibhav
