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Re: [Qemu-devel] [PATCH for-3.0 v2] pc: acpi: fix memory hotplug regress
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH for-3.0 v2] pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size |
Date: |
Mon, 30 Jul 2018 17:26:24 -0300 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
On Mon, Jul 30, 2018 at 11:41:41AM +0200, Igor Mammedov wrote:
> Commit 848a1cc1e (hw/acpi-build: build SRAT memory affinity structures for
> DIMM devices)
> broke the first dimm hotplug in following cases:
>
> 1: there is no coldplugged dimm in the last numa node
> but there is a coldplugged dimm in another node
>
> -m 4096,slots=4,maxmem=32G \
> -object memory-backend-ram,id=m0,size=2G \
> -device pc-dimm,memdev=m0,node=0 \
> -numa node,nodeid=0 \
> -numa node,nodeid=1
>
> 2: if order of dimms on CLI is:
> 1st plugged dimm in node1
> 2nd plugged dimm in node0
>
> -m 4096,slots=4,maxmem=32G \
> -object memory-backend-ram,size=2G,id=m0 \
> -device pc-dimm,memdev=m0,node=1 \
> -object memory-backend-ram,id=m1,size=2G \
> -device pc-dimm,memdev=m1,node=0 \
> -numa node,nodeid=0 \
> -numa node,nodeid=1
>
> (qemu) object_add memory-backend-ram,id=m2,size=1G
> (qemu) device_add pc-dimm,memdev=m2,node=0
>
> the first DIMM hotplug to any node except the last one
> fails (Windows is unable to online it).
>
> Length reduction of stub hotplug memory SRAT entry,
> fixes issue for some reason.
>
I'm really bothered by the lack of automated testing for all
these NUMA/ACPI corner cases.
This looks like a good candidate for an avocado_qemu test case.
Can you show pseudo-code of how exactly the bug fix could be
verified, so we can try to write a test case?
> RHBZ: 1609234
I suggest including full URL of bug report[1]. I doubt anybody
outside Red Hat knows what "RHBZ" means.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1609234
>
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> NOTE TO MAINTAINER: UPDATE REFERENCE APCI TABLE BLOBS
>
> v2:
> fixup examples in commit message
> (they were in wrong order and with duplicate memdev=m1)
> ---
> hw/i386/acpi-build.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 9e8350c..b52fdb2 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2269,7 +2269,16 @@ static void build_srat_hotpluggable_memory(GArray
> *table_data, uint64_t base,
> numamem = acpi_data_push(table_data, sizeof *numamem);
>
> if (!info) {
> - build_srat_memory(numamem, cur, end - cur, default_node,
> + /*
> + * 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;
> }
> @@ -2402,14 +2411,6 @@ 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,
> --
> 2.7.4
>
--
Eduardo