Re: [PATCH v2 6/8] pc: memhp: do not export nvdimm's memory via _CRS

From: Igor Mammedov <imammedo@redhat.com>
To: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Cc: pbonzini@redhat.com, gleb@kernel.org, mtosatti@redhat.com,
	stefanha@redhat.com, mst@redhat.com, rth@twiddle.net,
	ehabkost@redhat.com, dan.j.williams@intel.com,
	kvm@vger.kernel.org, qemu-devel@nongnu.org
Subject: Re: [PATCH v2 6/8] pc: memhp: do not export nvdimm's memory via _CRS
Date: Mon, 3 Oct 2016 15:21:54 +0200	[thread overview]
Message-ID: <20161003152154.03766fc1@nial.brq.redhat.com> (raw)
In-Reply-To: <1470984850-66891-7-git-send-email-guangrong.xiao@linux.intel.com>

On Fri, 12 Aug 2016 14:54:08 +0800
Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:

> nvdimm's memory info can not exported via _CRS, instead, it is reported
> by NFIT/FIT
> 
> This patch let _CRS return zero for both memory address and memory size
> if it is a nvdimm device inserted to the slot
I'm not sure if it's right thing to do.
As it's relatively new, spec isn't clear about NVDIMM hotplug
process and how it's related to PNP0C80 memory devices.

The thing is that notify to PNP0C80 will trigger regular
memory hotplug which would expect a valid _CRS and
I won't even try to predict reaction of different guests
on such behavior.

So far exposing NFIT was sufficient for guest to work with
NVDIMMs at startup. So I'd assume NVDIMM_ROOT._FIT() would
provide sufficient info to hot-plug NVDIMM and allow 
NVDIMM driver to handle it.

The only case of using PNP0C80 with NVDIMM, I'd imagine, is
when one would like to expose NVDIMM as conventional RAM and
make guest OS use it as such, which is probably not what you'd
intended do here.

Question is should/could NVDIMM hotplug work without using
PNP0C80?

One could reuse/share memhotplug GPE._E03 to notify NVDIMM_ROOT
but even that is not necessary as NVDIMM has its own QEMU<->guest
interface and could just take the next free _E04 handler.
So I'd suggest to redo this and 7/8 patches to implement
independent (of memhotplug) NVDIMM hotplug as a starting point.

> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> ---
>  hw/acpi/memory_hotplug.c         | 16 ++++++++++++----
>  include/hw/acpi/memory_hotplug.h |  1 +
>  2 files changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/acpi/memory_hotplug.c b/hw/acpi/memory_hotplug.c
> index ec4e64b..73fa62d 100644
> --- a/hw/acpi/memory_hotplug.c
> +++ b/hw/acpi/memory_hotplug.c
> @@ -2,6 +2,7 @@
>  #include "hw/acpi/memory_hotplug.h"
>  #include "hw/acpi/pc-hotplug.h"
>  #include "hw/mem/pc-dimm.h"
> +#include "hw/mem/nvdimm.h"
>  #include "hw/boards.h"
>  #include "hw/qdev-core.h"
>  #include "trace.h"
> @@ -41,6 +42,7 @@ void acpi_memory_ospm_status(MemHotplugState *mem_st, ACPIOSTInfoList ***list)
>  static uint64_t acpi_memory_hotplug_read(void *opaque, hwaddr addr,
>                                           unsigned int size)
>  {
> +    uint64_t maddr, msize;
>      uint32_t val = 0;
>      MemHotplugState *mem_st = opaque;
>      MemStatus *mdev;
> @@ -53,21 +55,25 @@ static uint64_t acpi_memory_hotplug_read(void *opaque, hwaddr addr,
>  
>      mdev = &mem_st->devs[mem_st->selector];
>      o = OBJECT(mdev->dimm);
> +    maddr = o && !mdev->is_nvdimm ? object_property_get_int(o,
> +                                        PC_DIMM_ADDR_PROP, NULL) : 0;
> +    msize = o && !mdev->is_nvdimm ? object_property_get_int(o,
> +                                        PC_DIMM_SIZE_PROP, NULL) : 0;
>      switch (addr) {
>      case 0x0: /* Lo part of phys address where DIMM is mapped */
> -        val = o ? object_property_get_int(o, PC_DIMM_ADDR_PROP, NULL) : 0;
> +        val = maddr;
>          trace_mhp_acpi_read_addr_lo(mem_st->selector, val);
>          break;
>      case 0x4: /* Hi part of phys address where DIMM is mapped */
> -        val = o ? object_property_get_int(o, PC_DIMM_ADDR_PROP, NULL) >> 32 : 0;
> +        val = maddr >> 32;
>          trace_mhp_acpi_read_addr_hi(mem_st->selector, val);
>          break;
>      case 0x8: /* Lo part of DIMM size */
> -        val = o ? object_property_get_int(o, PC_DIMM_SIZE_PROP, NULL) : 0;
> +        val = msize;
>          trace_mhp_acpi_read_size_lo(mem_st->selector, val);
>          break;
>      case 0xc: /* Hi part of DIMM size */
> -        val = o ? object_property_get_int(o, PC_DIMM_SIZE_PROP, NULL) >> 32 : 0;
> +        val = msize >> 32;
>          trace_mhp_acpi_read_size_hi(mem_st->selector, val);
>          break;
>      case 0x10: /* node proximity for _PXM method */
> @@ -78,6 +84,7 @@ static uint64_t acpi_memory_hotplug_read(void *opaque, hwaddr addr,
>          val |= mdev->is_enabled   ? 1 : 0;
>          val |= mdev->is_inserting ? 2 : 0;
>          val |= mdev->is_removing  ? 4 : 0;
> +        val |= mdev->is_nvdimm    ? 16 : 0;
>          trace_mhp_acpi_read_flags(mem_st->selector, val);
>          break;
>      default:
> @@ -245,6 +252,7 @@ void acpi_memory_plug_cb(HotplugHandler *hotplug_dev, MemHotplugState *mem_st,
>  
>      mdev->dimm = dev;
>      mdev->is_enabled = true;
> +    mdev->is_nvdimm = object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM);
>      if (dev->hotplugged) {
>          mdev->is_inserting = true;
>          acpi_send_event(DEVICE(hotplug_dev), ACPI_MEMORY_HOTPLUG_STATUS);
> diff --git a/include/hw/acpi/memory_hotplug.h b/include/hw/acpi/memory_hotplug.h
> index d2c7452..69a05df 100644
> --- a/include/hw/acpi/memory_hotplug.h
> +++ b/include/hw/acpi/memory_hotplug.h
> @@ -17,6 +17,7 @@ typedef struct MemStatus {
>      bool is_enabled;
>      bool is_inserting;
>      bool is_removing;
> +    bool is_nvdimm;
>      uint32_t ost_event;
>      uint32_t ost_status;
>  } MemStatus;