Re: [Qemu-devel] [PATCH] pc: acpi: revert back to 1 SRAT entry for hotpluggable area

[Igor Mammedov]

On Fri, 7 Sep 2018 16:44:34 -0400
"Michael S. Tsirkin" <address@hidden> wrote:

> On Wed, Aug 22, 2018 at 11:46:44AM +0200, Igor Mammedov wrote:
> > Commit
> >   10efd7e108 "pc: acpi: fix memory hotplug regression by reducing stub SRAT 
> > entry size"
> > attemped to fix hotplug regression introduced by
> >   848a1cc1e "hw/acpi-build: build SRAT memory affinity structures for DIMM 
> > devices"
> > 
> > fixed issue for Windows/3.0+ linux kernels, however it regressed 2.6 based
> > kernels (RHEL6) to the point where guest might crash at boot.
> > Reason is that 2.6 kernel discards SRAT table due too small last entry
> > which down the road leads to crashes. Hack I've tried in 10efd7e108 is also
> > not ACPI spec compliant according to which whole possible RAM should be
> > described in SRAT. Revert 10efd7e108 to fix regression for 2.6 based 
> > kernels.
> > 
> > With 10efd7e108 reverted, I've also tried splitting SRAT table statically
> > in different ways %/node and %/slot but Windows still fails to online
> > 2nd pc-dimm hot-plugged into node 0 (as described in 10efd7e108) and
> > sometimes even coldplugged pc-dimms where affected with static SRAT
> > partitioning.
> > The only known so far way where Windows stays happy is when we have 1
> > SRAT entry in the last node covering all hotplug area.
> > 
> > Revert 848a1cc1e until we come up with a way to avoid regression
> > on Windows with hotplug area split in several entries.
> > Tested this with 2.6/3.0 based kernels (RHEL6/7) and WS20[08/12/12R2/16]).
> > 
> > Signed-off-by: Igor Mammedov <address@hidden>  
> 
> BTW should this cause any aml test blobs to change?
> Does not seem to ...
test variants memhp and dimmpxm should be affected by this
(I see your pull req has relevant updates to reference SRAT tables)

> 
> > ---
> > CC: address@hidden
> > CC: address@hidden
> > CC: address@hidden
> > CC: address@hidden
> > CC: address@hidden
> > ---
> >  hw/i386/acpi-build.c | 73 
> > +++++++++-------------------------------------------
> >  1 file changed, 12 insertions(+), 61 deletions(-)
> > 
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index e1ee8ae..1599caa 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -2251,64 +2251,6 @@ build_tpm2(GArray *table_data, BIOSLinker *linker, 
> > GArray *tcpalog)
> >  #define HOLE_640K_START  (640 * KiB)
> >  #define HOLE_640K_END   (1 * MiB)
> >  
> > -static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t 
> > base,
> > -                                           uint64_t len, int default_node)
> > -{
> > -    MemoryDeviceInfoList *info_list = qmp_memory_device_list();
> > -    MemoryDeviceInfoList *info;
> > -    MemoryDeviceInfo *mi;
> > -    PCDIMMDeviceInfo *di;
> > -    uint64_t end = base + len, cur, size;
> > -    bool is_nvdimm;
> > -    AcpiSratMemoryAffinity *numamem;
> > -    MemoryAffinityFlags flags;
> > -
> > -    for (cur = base, info = info_list;
> > -         cur < end;
> > -         cur += size, info = info->next) {
> > -        numamem = acpi_data_push(table_data, sizeof *numamem);
> > -
> > -        if (!info) {
> > -            /*
> > -             * Entry is required for Windows to enable memory hotplug in OS
> > -             * and for Linux to enable SWIOTLB when booted with less than
> > -             * 4G of RAM. Windows works better if the entry sets proximity
> > -             * to the highest NUMA node in the machine at the end of the
> > -             * reserved space.
> > -             * Memory devices may override proximity set by this entry,
> > -             * providing _PXM method if necessary.
> > -             */
> > -            build_srat_memory(numamem, end - 1, 1, default_node,
> > -                              MEM_AFFINITY_HOTPLUGGABLE | 
> > MEM_AFFINITY_ENABLED);
> > -            break;
> > -        }
> > -
> > -        mi = info->value;
> > -        is_nvdimm = (mi->type == MEMORY_DEVICE_INFO_KIND_NVDIMM);
> > -        di = !is_nvdimm ? mi->u.dimm.data : mi->u.nvdimm.data;
> > -
> > -        if (cur < di->addr) {
> > -            build_srat_memory(numamem, cur, di->addr - cur, default_node,
> > -                              MEM_AFFINITY_HOTPLUGGABLE | 
> > MEM_AFFINITY_ENABLED);
> > -            numamem = acpi_data_push(table_data, sizeof *numamem);
> > -        }
> > -
> > -        size = di->size;
> > -
> > -        flags = MEM_AFFINITY_ENABLED;
> > -        if (di->hotpluggable) {
> > -            flags |= MEM_AFFINITY_HOTPLUGGABLE;
> > -        }
> > -        if (is_nvdimm) {
> > -            flags |= MEM_AFFINITY_NON_VOLATILE;
> > -        }
> > -
> > -        build_srat_memory(numamem, di->addr, size, di->node, flags);
> > -    }
> > -
> > -    qapi_free_MemoryDeviceInfoList(info_list);
> > -}
> > -
> >  static void
> >  build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> >  {
> > @@ -2414,10 +2356,19 @@ build_srat(GArray *table_data, BIOSLinker *linker, 
> > MachineState *machine)
> >          build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
> >      }
> >  
> > +    /*
> > +     * Entry is required for Windows to enable memory hotplug in OS
> > +     * and for Linux to enable SWIOTLB when booted with less than
> > +     * 4G of RAM. Windows works better if the entry sets proximity
> > +     * to the highest NUMA node in the machine.
> > +     * Memory devices may override proximity set by this entry,
> > +     * providing _PXM method if necessary.
> > +     */
> >      if (hotplugabble_address_space_size) {
> > -        build_srat_hotpluggable_memory(table_data, 
> > machine->device_memory->base,
> > -                                       hotplugabble_address_space_size,
> > -                                       pcms->numa_nodes - 1);
> > +        numamem = acpi_data_push(table_data, sizeof *numamem);
> > +        build_srat_memory(numamem, machine->device_memory->base,
> > +                          hotplugabble_address_space_size, 
> > pcms->numa_nodes - 1,
> > +                          MEM_AFFINITY_HOTPLUGGABLE | 
> > MEM_AFFINITY_ENABLED);
> >      }
> >  
> >      build_header(linker, table_data,
> > -- 
> > 2.7.4  
>