[PATCH v9 0/7] i386: Enable TOPOEXT to support hyperthreading on AMD CPU

Babu Moger
2018-05-14T16:41:49Z

This series enables the TOPOEXT feature for AMD CPUs. This is required to
support hyperthreading on kvm guests.

This addresses the issues reported in these bugs:
https://bugzilla.redhat.com/show_bug.cgi?id=1481253
https://bugs.launchpad.net/qemu/+bug/1703506

v9:
Based the patches on Eduardo's git://github.com/ehabkost/qemu.git x86-next
tree. Following 3 patches from v8 are already queued.
i386: Add cache information in X86CPUDefinition
i386: Initialize cache information for EPYC family processors
i386: Helpers to encode cache information consistently
So, submitting the rest of the series here.

Changes:
1. Included Eduardo's clean up patch
2. Added 2.13 machine types
3. Disabled topoext for 2.12 and below versions.
4. Added the assert to core_id as discussed.

v8:
Addressed feedback from Eduardo. Thanks Eduardo for being patient with me.
Tested on AMD EPYC server and also did some basic testing on intel box.
Summary of changes.
1. Reverted back l2 cache associativity. Kept it same as legacy.
2. Changed cache_info structure in X86CPUDefinition and CPUX86State to pointers.
3. Added legacy_cache property in PC_COMPAT_2_12 and initialized legacy_cache
based on static cache_info availability.
4. Squashed patch 4 and 5 and applied it before patch 3.
5. Added legacy cache check for cpuid[2] and cpuid[4] for consistancy.
6. Simplified NUM_SHARING_CACHE definition for readability,
7. Removed assert for core_id as it appeared redundant.
8. Simplified encode_cache_cpuid8000001d little bit.
9. Few more minor changes

v7:
Rebased on top of latest tree after 2.12 release and done few basic tests. There are
no changes except for few minor hunks. Hopefully this gets pulled into 2.13 release.
Please review, let me know of any feedback.

v6:
1.Fixed problem with patch#4(Add new property to control cache info). The parameter
legacy_cache should be "on" by default on machine type "pc-q35-2.10". This was
found by Alexandr Iarygin.
2.Fixed the l3 cache size for EPYC based machines(patch#3). Also, fixed the number of
logical processors sharing the cache(patch#6). Only L3 cache is shared by multiple
cores but not L1 or L2. This was a bug while decoding. This was found by Geoffrey McRae
and he verified the fix.

v5:
In this series I tried to address the feedback from Eduardo Habkost.
The discussion thread is here.
https://patchwork.kernel.org/patch/10299745/
The previous thread is here.
http://patchwork.ozlabs.org/cover/884885/

Reason for these changes.
The cache properties for AMD family of processors have changed from
previous releases. We don't want to display the new information on the
old family of processors as this might cause compatibility issues.

Changes:
1.Based the patches on top of Eduardo's(patch#1) patch.
Changed few things.
Moved the Cache definitions to cpu.h file.
Changed the CPUID_4 names to generic names.
2.Added a new propery "legacy-cache" in cpu object(patch#2). This can be
used to display the old property even if the host supports the new cache
properties.
3.Added cache information in X86CPUDefinition and CPUX86State
4.Patch 6-7 changed quite a bit from previous version does to new approach.
5.Addressed few issues with CPUID_8000_001d and CPUID_8000_001E.

v4:
1.Removed the checks under cpuid 0x8000001D leaf(patch #2). These check are
not necessary. Found this during internal review.
2.Added CPUID_EXT3_TOPOEXT feature for all the 17 family(patch #4). This was
found by Kash Pande during his testing.
3.Removed th hardcoded cpuid xlevel and dynamically extended if CPUID_EXT3_TOPOEXT
is supported(Suggested by Brijesh Singh).

v3:
1.Removed the patch #1. Radim mentioned that original typo problem is in
linux kernel header. qemu is just copying those files.
2.In previous version, I used the cpuid 4 definitions for AMDs cpuid leaf
0x8000001D. CPUID 4 is very intel specific and we dont want to expose those
details under AMD. I have renamed some of these definitions as generic.
These changes are in patch#1. Radim, let me know if this is what you intended.
3.Added assert to for core_id(Suggested by Radim Krcmár).
4.Changed the if condition under "L3 cache info"(Suggested by Gary Hook).
5.Addressed few more text correction and code cleanup(Suggested by Thomas Lendacky).

v2:
Fixed few more minor issues per Gary Hook's comments. Thank you Gary.
Removed the patch#1. We need to handle the instruction cache associativity
seperately. It varies based on the cpu family. I will comeback to that later.
Added two more typo corrections in patch#1 and patch#5.

v1:
Stanislav Lanci posted few patches earlier.
https://patchwork.kernel.org/patch/10040903/

Rebased his patches with few changes.
1.Spit the patches into two, separating cpuid functions
0x8000001D and 0x8000001E (Patch 2 and 3).
2.Removed the generic non-intel check and made a separate patch
with some changes(Patch 5).
3.Fixed L3_N_SETS_AMD(from 4096 to 8192) based on CPUID_Fn8000001D_ECX_x03.

Added 2 more patches.
Patch 1. Fixes cache associativity.
Patch 4. Adds TOPOEXT feature on AMD EPYC CPU.

Babu Moger (6):
pc: add 2.13 machine types
i386: Add new property to control cache info
i386: Populate AMD Processor Cache Information for cpuid 0x8000001D
i386: Add support for CPUID_8000_001E for AMD
i386: Enable TOPOEXT feature on AMD EPYC CPU
i386: Remove generic SMT thread check

Eduardo Habkost (1):
i386: Clean up cache CPUID code

hw/i386/pc_piix.c | 15 ++-
hw/i386/pc_q35.c | 13 ++-
include/hw/i386/pc.h | 12 +++
include/hw/i386/topology.h | 6 ++
target/i386/cpu.c | 195 ++++++++++++++++++++++++++++++-------
target/i386/cpu.h | 19 +++-
target/i386/kvm.c | 29 +++++-
7 files changed, 243 insertions(+), 46 deletions(-)

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2.17.0