[PATCH v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[PATCH v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[Leonardo Bras]

On reboot, all memory that was previously added using object_add and
device_add is placed in this DIMM area.

The new SPAPR_LMB_FLAGS_HOTREMOVABLE flag helps Linux to put this memory in
the correct memory zone, so no unmovable allocations are made there,
allowing the object to be easily hot-removed by device_del and
object_del.

This new flag was accepted in Power Architecture documentation.

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>

---
Changes since v1:
- Flag name changed from SPAPR_LMB_FLAGS_HOTPLUGGED to
	SPAPR_LMB_FLAGS_HOTREMOVABLE
---
 hw/ppc/spapr.c         | 3 ++-
 include/hw/ppc/spapr.h | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 9a2bd501aa..fe662e297e 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -446,7 +446,8 @@ static int spapr_dt_dynamic_memory_v2(SpaprMachineState *spapr, void *fdt,
         g_assert(drc);
         elem = spapr_get_drconf_cell(size / lmb_size, addr,
                                      spapr_drc_index(drc), node,
-                                     SPAPR_LMB_FLAGS_ASSIGNED);
+                                     (SPAPR_LMB_FLAGS_ASSIGNED |
+                                      SPAPR_LMB_FLAGS_HOTREMOVABLE);
         QSIMPLEQ_INSERT_TAIL(&drconf_queue, elem, entry);
         nr_entries++;
         cur_addr = addr + size;
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 42d64a0368..93e0d43051 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -880,6 +880,7 @@ int spapr_rtc_import_offset(SpaprRtcState *rtc, int64_t legacy_offset);
 #define SPAPR_LMB_FLAGS_ASSIGNED 0x00000008
 #define SPAPR_LMB_FLAGS_DRC_INVALID 0x00000020
 #define SPAPR_LMB_FLAGS_RESERVED 0x00000080
+#define SPAPR_LMB_FLAGS_HOTREMOVABLE 0x00000100
 
 void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
 
-- 
2.25.1

Re: [PATCH v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[David Gibson]

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On Thu, Apr 02, 2020 at 02:23:40PM -0300, Leonardo Bras wrote:
> On reboot, all memory that was previously added using object_add and
> device_add is placed in this DIMM area.
> 
> The new SPAPR_LMB_FLAGS_HOTREMOVABLE flag helps Linux to put this memory in
> the correct memory zone, so no unmovable allocations are made there,
> allowing the object to be easily hot-removed by device_del and
> object_del.
> 
> This new flag was accepted in Power Architecture documentation.
> 
> Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
> Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>

The change looks reasonable.  Is there a PAPR RFC I can see describing
the new bit, though?

> ---
> Changes since v1:
> - Flag name changed from SPAPR_LMB_FLAGS_HOTPLUGGED to
> 	SPAPR_LMB_FLAGS_HOTREMOVABLE
> ---
>  hw/ppc/spapr.c         | 3 ++-
>  include/hw/ppc/spapr.h | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 9a2bd501aa..fe662e297e 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -446,7 +446,8 @@ static int spapr_dt_dynamic_memory_v2(SpaprMachineState *spapr, void *fdt,
>          g_assert(drc);
>          elem = spapr_get_drconf_cell(size / lmb_size, addr,
>                                       spapr_drc_index(drc), node,
> -                                     SPAPR_LMB_FLAGS_ASSIGNED);
> +                                     (SPAPR_LMB_FLAGS_ASSIGNED |
> +                                      SPAPR_LMB_FLAGS_HOTREMOVABLE);
>          QSIMPLEQ_INSERT_TAIL(&drconf_queue, elem, entry);
>          nr_entries++;
>          cur_addr = addr + size;
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 42d64a0368..93e0d43051 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -880,6 +880,7 @@ int spapr_rtc_import_offset(SpaprRtcState *rtc, int64_t legacy_offset);
>  #define SPAPR_LMB_FLAGS_ASSIGNED 0x00000008
>  #define SPAPR_LMB_FLAGS_DRC_INVALID 0x00000020
>  #define SPAPR_LMB_FLAGS_RESERVED 0x00000080
> +#define SPAPR_LMB_FLAGS_HOTREMOVABLE 0x00000100
>  
>  void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
>  

-- 
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 v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[Leonardo Bras]

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Hello David,

On Fri, 2020-04-03 at 09:49 +1100, David Gibson wrote:
> 
> The change looks reasonable.  Is there a PAPR RFC I can see describing
> the new bit, though?

The ACR is approved and I already added the change to LoPAPR/LOPAR,
it's just a matter of time to get it released.
(I think it's accessible to members of OpenPower Foundation)

This is the snippet of the change:

At the bottom of "Table 3.11: Flag Word", add another line containing:
Hot-removable Memory	| 0x00000100 	| If b'1', this LMB can be hot-
removed. 
			|		| If b'0', this LMB may not be hot-
removed

Best regards,
Leonardo Bras

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Re: [PATCH v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[David Gibson]

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On Thu, Apr 02, 2020 at 08:00:57PM -0300, Leonardo Bras wrote:
> Hello David,
> 
> On Fri, 2020-04-03 at 09:49 +1100, David Gibson wrote:
> > 
> > The change looks reasonable.  Is there a PAPR RFC I can see describing
> > the new bit, though?
> 
> The ACR is approved and I already added the change to LoPAPR/LOPAR,
> it's just a matter of time to get it released.
> (I think it's accessible to members of OpenPower Foundation)

Hrm.  The latest LoPAPR I can find is from 2016, so a "matter of time"
isn't very encouraging.

> 
> This is the snippet of the change:
> 
> At the bottom of "Table 3.11: Flag Word", add another line containing:
> Hot-removable Memory	| 0x00000100 	| If b'1', this LMB can be hot-
> removed. 
> 			|		| If b'0', this LMB may not be hot-
> removed
> 
> Best regards,
> Leonardo Bras



-- 
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 v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[Leonardo Bras]

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On Fri, 2020-04-03 at 10:16 +1100, David Gibson wrote:
> On Thu, Apr 02, 2020 at 08:00:57PM -0300, Leonardo Bras wrote:
> > Hello David,
> > 
> > On Fri, 2020-04-03 at 09:49 +1100, David Gibson wrote:
> > > The change looks reasonable.  Is there a PAPR RFC I can see describing
> > > the new bit, though?
> > 
> > The ACR is approved and I already added the change to LoPAPR/LOPAR,
> > it's just a matter of time to get it released.
> > (I think it's accessible to members of OpenPower Foundation)
> 
> Hrm.  The latest LoPAPR I can find is from 2016, so a "matter of time"
> isn't very encouraging.

I understand the feeling.
There is a new initiative inside the OpenPower Foundation to keep these
documents updated. 

I think we will be able to have more frequent updates of the
documentation soon.

Best Regards,

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Re: [PATCH v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[David Gibson]

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On Thu, Apr 02, 2020 at 08:19:34PM -0300, Leonardo Bras wrote:
> On Fri, 2020-04-03 at 10:16 +1100, David Gibson wrote:
> > On Thu, Apr 02, 2020 at 08:00:57PM -0300, Leonardo Bras wrote:
> > > Hello David,
> > > 
> > > On Fri, 2020-04-03 at 09:49 +1100, David Gibson wrote:
> > > > The change looks reasonable.  Is there a PAPR RFC I can see describing
> > > > the new bit, though?
> > > 
> > > The ACR is approved and I already added the change to LoPAPR/LOPAR,
> > > it's just a matter of time to get it released.
> > > (I think it's accessible to members of OpenPower Foundation)
> > 
> > Hrm.  The latest LoPAPR I can find is from 2016, so a "matter of time"
> > isn't very encouraging.
> 
> I understand the feeling.
> There is a new initiative inside the OpenPower Foundation to keep these
> documents updated. 
> 
> I think we will be able to have more frequent updates of the
> documentation soon.

Urgh.  Ok, I'm sorry Leonardo, but,

Nack.  I will not merge a change where my only knowledge of the spec
has to be based on hearsay.

By all means use this as ammunition to convince IBM and/or the
openpower foundation to expedite getting a workable document release
process up and running.

-- 
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 v3 1/1] ppc/spapr: Add hotremovable flag on DIMM LMBs on drmem_v2

[Leonardo Bras]

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On Fri, 2020-04-03 at 10:40 +1100, David Gibson wrote:
> Urgh.  Ok, I'm sorry Leonardo, but,
> 
> Nack.  I will not merge a change where my only knowledge of the spec
> has to be based on hearsay.
> 
> By all means use this as ammunition to convince IBM and/or the
> openpower foundation to expedite getting a workable document release
> process up and running.

No problem David, of course I understand your point.

I am working on this document release, and it will probably be
available soon. 

When it is, we can visit this patch again.

Best regards,
Leonardo Bras

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