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

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

[Vaibhav Jain]

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;
+    }
+
+    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;
+
+    /* health bitmap mask same as the health bitmap */
+    args[1] = args[0];
+
+    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.
-- 
2.30.2

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

[Vaibhav Jain]

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;
+    }
+
+    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;
+
+    /* health bitmap mask same as the health bitmap */
+    args[1] = args[0];
+
+    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.
-- 
2.30.2

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

[Shivaprasad G Bhat]

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

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

[Shivaprasad G Bhat]

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

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

[Vaibhav Jain]

Hi Shiva,

Thanks for reviweing this patch. My responses inline below;


Shivaprasad G Bhat <sbhat@linux.ibm.com> writes:

<snip>

>>   
>> +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.
>
>
Sure, will address that in v2

>> +    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.
>
>
Sure I will switch to object_property_get_bool in v2. However I see
nvdimm->unarmed being accessed in similar manner in
nvdimm_build_structure_memdev() which probably needs an update too.

<snip>

-- 
Cheers
~ Vaibhav

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

[Vaibhav Jain]

Hi Shiva,

Thanks for reviweing this patch. My responses inline below;


Shivaprasad G Bhat <sbhat@linux.ibm.com> writes:

<snip>

>>   
>> +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.
>
>
Sure, will address that in v2

>> +    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.
>
>
Sure I will switch to object_property_get_bool in v2. However I see
nvdimm->unarmed being accessed in similar manner in
nvdimm_build_structure_memdev() which probably needs an update too.

<snip>

-- 
Cheers
~ Vaibhav

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

[Greg Kurz]

Hi Vaibhav,

Great to see you around :-)

On Mon, 29 Mar 2021 21:52:59 +0530
Vaibhav Jain <vaibhav@linux.ibm.com> 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 ?

> 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))

This looks like PPC_BIT(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;
> +    }
> +
> +    nvdimm = NVDIMM(drc->dev);

Yeah as already suggested by Shiva, drc->dev should be checked like
in h_scm_bind_mem().

> +
> +    /* 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.

Having access to the excerpts from the PAPR addendum that describes
this hcall would _really_ help in reviewing.

> +    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.

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

[Greg Kurz]

Hi Vaibhav,

Great to see you around :-)

On Mon, 29 Mar 2021 21:52:59 +0530
Vaibhav Jain <vaibhav@linux.ibm.com> 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 ?

> 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))

This looks like PPC_BIT(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;
> +    }
> +
> +    nvdimm = NVDIMM(drc->dev);

Yeah as already suggested by Shiva, drc->dev should be checked like
in h_scm_bind_mem().

> +
> +    /* 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.

Having access to the excerpts from the PAPR addendum that describes
this hcall would _really_ help in reviewing.

> +    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.

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

[Vaibhav Jain]

Thanks for looking into this patch Greg. My responses below inline.


Greg Kurz <groug@kaod.org> writes:

> Hi Vaibhav,
>
> Great to see you around :-)

:-)

>
> On Mon, 29 Mar 2021 21:52:59 +0530
> Vaibhav Jain <vaibhav@linux.ibm.com> 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@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))
>
> 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

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

[Vaibhav Jain]

Thanks for looking into this patch Greg. My responses below inline.


Greg Kurz <groug@kaod.org> writes:

> Hi Vaibhav,
>
> Great to see you around :-)

:-)

>
> On Mon, 29 Mar 2021 21:52:59 +0530
> Vaibhav Jain <vaibhav@linux.ibm.com> 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@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))
>
> 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

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

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 5403 bytes --]

On Tue, Mar 30, 2021 at 10:37:06PM +0530, Vaibhav Jain wrote:
> 
> Thanks for looking into this patch Greg. My responses below inline.
> 
> 
> Greg Kurz <groug@kaod.org> writes:
> 
> > Hi Vaibhav,
> >
> > Great to see you around :-)
> 
> :-)
> 
> >
> > On Mon, 29 Mar 2021 21:52:59 +0530
> > Vaibhav Jain <vaibhav@linux.ibm.com> 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

Putting a reference to that in the commit message would be a good idea.

> 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@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))
> >
> > 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.

We've missed the qemu-6.0 cutoff, so this will be 6.1 material.  I'll
await v2 for further review.

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

[David Gibson]

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On Tue, Mar 30, 2021 at 10:37:06PM +0530, Vaibhav Jain wrote:
> 
> Thanks for looking into this patch Greg. My responses below inline.
> 
> 
> Greg Kurz <groug@kaod.org> writes:
> 
> > Hi Vaibhav,
> >
> > Great to see you around :-)
> 
> :-)
> 
> >
> > On Mon, 29 Mar 2021 21:52:59 +0530
> > Vaibhav Jain <vaibhav@linux.ibm.com> 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

Putting a reference to that in the commit message would be a good idea.

> 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@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))
> >
> > 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.

We've missed the qemu-6.0 cutoff, so this will be 6.1 material.  I'll
await v2 for further review.

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

[Vaibhav Jain]

Thanks for looking into this patch,

David Gibson <david@gibson.dropbear.id.au> writes:

<snip>
>> 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
>
> Putting a reference to that in the commit message would be a good idea.
>
Yes, its already part of v1 patch description as reference [1].

<snip>
>> >
>> > 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.
>
> We've missed the qemu-6.0 cutoff, so this will be 6.1 material.  I'll
> await v2 for further review.
>
Agree. Will send a v2 today incorporating current review comments.


-- 
Cheers
~ Vaibhav

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

[Vaibhav Jain]

Thanks for looking into this patch,

David Gibson <david@gibson.dropbear.id.au> writes:

<snip>
>> 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
>
> Putting a reference to that in the commit message would be a good idea.
>
Yes, its already part of v1 patch description as reference [1].

<snip>
>> >
>> > 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.
>
> We've missed the qemu-6.0 cutoff, so this will be 6.1 material.  I'll
> await v2 for further review.
>
Agree. Will send a v2 today incorporating current review comments.


-- 
Cheers
~ Vaibhav

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

[Greg Kurz]

On Tue, 30 Mar 2021 22:37:06 +0530
Vaibhav Jain <vaibhav@linux.ibm.com> wrote:

> 
> Thanks for looking into this patch Greg. My responses below inline.
> 
> 
> Greg Kurz <groug@kaod.org> writes:
> 
> > Hi Vaibhav,
> >
> > Great to see you around :-)
> 
> :-)
> 
> >
> > On Mon, 29 Mar 2021 21:52:59 +0530
> > Vaibhav Jain <vaibhav@linux.ibm.com> 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. 
> 

Oops I skipped that indeed. Maybe even make it:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst#n220

for faster access.

> >> 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))
> >
> > This looks like PPC_BIT(0).
> >
> Yes, right. Will update the patch in v2 to use the PPC_BIT macro.
> 

Well, since this was copied from the kernel sources, I guess you can
leave it as is. Maybe just explain where this macro comes from if you
do so.

> >> +
> >> +/* 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.
> 

After a deeper look into the kernel documentation and code, it seems that
we really don't need PAPR_PMEM_UNARMED_MASK at all on the QEMU side : it
is _just_ the mask of bits that linux does support (i.e. bit 0 and 6) and
applies to the health bitmap returned by H_SCM_HEALTH.

On the QEMU side, as you say, we just support setting bit 0 from the
time being : args[0] should thus be set to PAPR_PMEM_UNARMED if the
NVDIMM is unarmed, not PAPR_PMEM_UNARMED_MASK.

Also, it seems that the purpose of the health bitmap mask is to tell the
guest about the bits supported by the hypervisor : args[1] should thus
unconditionally be set to PAPR_PMEM_UNARMED, otherwise we'd tell the
guest none of the bits are valid when the NVDIMM isn't unarmed.

> >
> > 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.
> 

Sorry again for having missed the link the first time. I guess I have all
the information I need now.

> 
> >> +    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.
> >
> 

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

[Greg Kurz]

On Tue, 30 Mar 2021 22:37:06 +0530
Vaibhav Jain <vaibhav@linux.ibm.com> wrote:

> 
> Thanks for looking into this patch Greg. My responses below inline.
> 
> 
> Greg Kurz <groug@kaod.org> writes:
> 
> > Hi Vaibhav,
> >
> > Great to see you around :-)
> 
> :-)
> 
> >
> > On Mon, 29 Mar 2021 21:52:59 +0530
> > Vaibhav Jain <vaibhav@linux.ibm.com> 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. 
> 

Oops I skipped that indeed. Maybe even make it:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst#n220

for faster access.

> >> 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))
> >
> > This looks like PPC_BIT(0).
> >
> Yes, right. Will update the patch in v2 to use the PPC_BIT macro.
> 

Well, since this was copied from the kernel sources, I guess you can
leave it as is. Maybe just explain where this macro comes from if you
do so.

> >> +
> >> +/* 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.
> 

After a deeper look into the kernel documentation and code, it seems that
we really don't need PAPR_PMEM_UNARMED_MASK at all on the QEMU side : it
is _just_ the mask of bits that linux does support (i.e. bit 0 and 6) and
applies to the health bitmap returned by H_SCM_HEALTH.

On the QEMU side, as you say, we just support setting bit 0 from the
time being : args[0] should thus be set to PAPR_PMEM_UNARMED if the
NVDIMM is unarmed, not PAPR_PMEM_UNARMED_MASK.

Also, it seems that the purpose of the health bitmap mask is to tell the
guest about the bits supported by the hypervisor : args[1] should thus
unconditionally be set to PAPR_PMEM_UNARMED, otherwise we'd tell the
guest none of the bits are valid when the NVDIMM isn't unarmed.

> >
> > 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.
> 

Sorry again for having missed the link the first time. I guess I have all
the information I need now.

> 
> >> +    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.
> >
>